BMI
Replies
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mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
do you understand statistics at all and standard deviations? 25% of the population will fit into typically 1 standard deviation of the avg population - which is why they pick that range
I do understand statistics. Do you understand the art of reading a post properly and understanding it?
I'm talking about giving specific advice to individuals based on their personal circumstances. It's foolish to apply an average to an individual. Imagine what the world would be like if everyone actually had 2.4 children......
maybe that is something to take up with your medical professional then - because i know my doctor doesn't just give me advice based on BMI - she considers results of body fat assessment (done via a dexa scan and also bodpod); as well as food intake - and if she did, she wouldn't be my doctor much longer
BMI is a statistical tool that can provide initial assessment to see whether an individual potentially falls into an increased risk category for health issues (either from being under or over weight).
wow these replies are coming through quick, I'll try my best to keep up!
It would seem you and I are in agreement then, BMI isn't that much of a useful tool. You need other means of testing to understand the bigger picture.
you're talking about about throwing the baby out with the bathwater because it doesn't fit your perception of useful
I'm not sure that's the case. Your doctor gives you advice based on BMI as well as other means of assessment. The instances I'm referring to treat BMI as a single wonder number on it's own with no other questions asked
show me where in this thread or elsewhere on MFP that anyone has advocated taking only BMI as a factor in determining weight?10 -
mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
do you understand statistics at all and standard deviations? 25% of the population will fit into typically 1 standard deviation of the avg population - which is why they pick that range
I do understand statistics. Do you understand the art of reading a post properly and understanding it?
I'm talking about giving specific advice to individuals based on their personal circumstances. It's foolish to apply an average to an individual. Imagine what the world would be like if everyone actually had 2.4 children......
maybe that is something to take up with your medical professional then - because i know my doctor doesn't just give me advice based on BMI - she considers results of body fat assessment (done via a dexa scan and also bodpod); as well as food intake - and if she did, she wouldn't be my doctor much longer
BMI is a statistical tool that can provide initial assessment to see whether an individual potentially falls into an increased risk category for health issues (either from being under or over weight).
wow these replies are coming through quick, I'll try my best to keep up!
It would seem you and I are in agreement then, BMI isn't that much of a useful tool. You need other means of testing to understand the bigger picture.
I don't think anyone is arguing anything other than that. I certainly wouldn't, as that's not what BMI was intended for other than as an initial assessment. However, most people in these forums don't provide us with the results of their full workup at the their last doctor's visit so all we have to make an assessment are height, weight age and stated activity level.
Also, BMI, itself, isn't much of a useful tool, but it is a useful tool to make an initial assessment. It's also useful for making recommendations when you have no better information to go on.
That's a really interesting point. In my experience in reading these forums it tends to be the people replying who say "whats your height and weight, we can work out your BMI" .....rather than saying "tell us some more useful information so that we can properly help you".
But if it isnt that useful then why use it as an initial assessment? Why not get straight in to the details rather than starting to give advice based on some assumption gained from a tool that isnt useful, as you said5 -
mattrus1989 wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
do you understand statistics at all and standard deviations? 25% of the population will fit into typically 1 standard deviation of the avg population - which is why they pick that range
I do understand statistics. Do you understand the art of reading a post properly and understanding it?
I'm talking about giving specific advice to individuals based on their personal circumstances. It's foolish to apply an average to an individual. Imagine what the world would be like if everyone actually had 2.4 children......
maybe that is something to take up with your medical professional then - because i know my doctor doesn't just give me advice based on BMI - she considers results of body fat assessment (done via a dexa scan and also bodpod); as well as food intake - and if she did, she wouldn't be my doctor much longer
BMI is a statistical tool that can provide initial assessment to see whether an individual potentially falls into an increased risk category for health issues (either from being under or over weight).
wow these replies are coming through quick, I'll try my best to keep up!
It would seem you and I are in agreement then, BMI isn't that much of a useful tool. You need other means of testing to understand the bigger picture.
I don't think anyone is arguing anything other than that. I certainly wouldn't, as that's not what BMI was intended for other than as an initial assessment. However, most people in these forums don't provide us with the results of their full workup at the their last doctor's visit so all we have to make an assessment are height, weight age and stated activity level.
Also, BMI, itself, isn't much of a useful tool, but it is a useful tool to make an initial assessment. It's also useful for making recommendations when you have no better information to go on.
That's a really interesting point. In my experience in reading these forums it tends to be the people replying who say "whats your height and weight, we can work out your BMI" .....rather than saying "tell us some more useful information so that we can properly help you".
But if it isnt that useful then why use it as an initial assessment? Why not get straight in to the details rather than starting to give advice based on some assumption gained from a tool that isnt useful, as you said
because very few people on the forum likely have immediate access to a facility where body fat or VO2Max or BMR etc - can be assessed - so asking for BMI is an initial look-see and then further recommendations can be made11 -
deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
do you understand statistics at all and standard deviations? 25% of the population will fit into typically 1 standard deviation of the avg population - which is why they pick that range
I do understand statistics. Do you understand the art of reading a post properly and understanding it?
I'm talking about giving specific advice to individuals based on their personal circumstances. It's foolish to apply an average to an individual. Imagine what the world would be like if everyone actually had 2.4 children......
maybe that is something to take up with your medical professional then - because i know my doctor doesn't just give me advice based on BMI - she considers results of body fat assessment (done via a dexa scan and also bodpod); as well as food intake - and if she did, she wouldn't be my doctor much longer
BMI is a statistical tool that can provide initial assessment to see whether an individual potentially falls into an increased risk category for health issues (either from being under or over weight).
wow these replies are coming through quick, I'll try my best to keep up!
It would seem you and I are in agreement then, BMI isn't that much of a useful tool. You need other means of testing to understand the bigger picture.
I don't think anyone is arguing anything other than that. I certainly wouldn't, as that's not what BMI was intended for other than as an initial assessment. However, most people in these forums don't provide us with the results of their full workup at the their last doctor's visit so all we have to make an assessment are height, weight age and stated activity level.
Also, BMI, itself, isn't much of a useful tool, but it is a useful tool to make an initial assessment. It's also useful for making recommendations when you have no better information to go on.
That's a really interesting point. In my experience in reading these forums it tends to be the people replying who say "whats your height and weight, we can work out your BMI" .....rather than saying "tell us some more useful information so that we can properly help you".
But if it isnt that useful then why use it as an initial assessment? Why not get straight in to the details rather than starting to give advice based on some assumption gained from a tool that isnt useful, as you said
because very few people on the forum likely have immediate access to a facility where body fat or VO2Max or BMR etc - can be assessed - so asking for BMI is an initial look-see and then further recommendations can be made
There are plenty of examples of what I've said, you will come across them pretty quickly. I can barely keep up with the speed of these comments, let alone search the forum for all past threads I've read too.
My point still remains that the "initial look see" can still be wrong, so it seems useless to start with it at all.
It seems we have probably reached the point where we have to agree to disagree. Hopefully this link sums up some of my thoughts (about BMI, not shape index, I don't know anything about that)
https://shapescale.com/blog/health/why-bmi-is-wrong-and-shape-index-is-telling-the-truth/6 -
mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
do you understand statistics at all and standard deviations? 25% of the population will fit into typically 1 standard deviation of the avg population - which is why they pick that range
I do understand statistics. Do you understand the art of reading a post properly and understanding it?
I'm talking about giving specific advice to individuals based on their personal circumstances. It's foolish to apply an average to an individual. Imagine what the world would be like if everyone actually had 2.4 children......
Except mfp really isn't specific advice to individuals based on their personal circumstances... It's an internet forum with a wide range of users, with a wide range of personal experiences, and a wide range of capabilities (intellectual or otherwise). Speaking in the generalities of BMI is enough for plenty of the users here--these are people who ask if raspberry ketones or the HCG diet will work. People who have a good idea of where they want to go and what they want to do, health- and weight-wise, are working with trainers, dietitians, etc. outside of mfp and aren't on here asking random internet strangers for advice on BMI.
Sorry, I missed your message.
In large part, I agree. Which is why I still concede that I understand how BMI can be rolled out as a very general rule of thumb for a massive audience with a huge range of variation.
However, the minute a single person asks a question and a single person responds, surely that response can be slightly tailored to the individual. If it wasnt then why not close the forum and just redirect everyone to a bmi calculator?2 -
mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
do you understand statistics at all and standard deviations? 25% of the population will fit into typically 1 standard deviation of the avg population - which is why they pick that range
I do understand statistics. Do you understand the art of reading a post properly and understanding it?
I'm talking about giving specific advice to individuals based on their personal circumstances. It's foolish to apply an average to an individual. Imagine what the world would be like if everyone actually had 2.4 children......
maybe that is something to take up with your medical professional then - because i know my doctor doesn't just give me advice based on BMI - she considers results of body fat assessment (done via a dexa scan and also bodpod); as well as food intake - and if she did, she wouldn't be my doctor much longer
BMI is a statistical tool that can provide initial assessment to see whether an individual potentially falls into an increased risk category for health issues (either from being under or over weight).
wow these replies are coming through quick, I'll try my best to keep up!
It would seem you and I are in agreement then, BMI isn't that much of a useful tool. You need other means of testing to understand the bigger picture.
I don't think anyone is arguing anything other than that. I certainly wouldn't, as that's not what BMI was intended for other than as an initial assessment. However, most people in these forums don't provide us with the results of their full workup at the their last doctor's visit so all we have to make an assessment are height, weight age and stated activity level.
Also, BMI, itself, isn't much of a useful tool, but it is a useful tool to make an initial assessment. It's also useful for making recommendations when you have no better information to go on.
That's a really interesting point. In my experience in reading these forums it tends to be the people replying who say "whats your height and weight, we can work out your BMI" .....rather than saying "tell us some more useful information so that we can properly help you".
But if it isnt that useful then why use it as an initial assessment? Why not get straight in to the details rather than starting to give advice based on some assumption gained from a tool that isnt useful, as you said
because very few people on the forum likely have immediate access to a facility where body fat or VO2Max or BMR etc - can be assessed - so asking for BMI is an initial look-see and then further recommendations can be made
There are plenty of examples of what I've said, you will come across them pretty quickly. I can barely keep up with the speed of these comments, let alone search the forum for all past threads I've read too.
My point still remains that the "initial look see" can still be wrong, so it seems useless to start with it at all.
It seems we have probably reached the point where we have to agree to disagree. Hopefully this link sums up some of my thoughts (about BMI, not shape index, I don't know anything about that)
https://shapescale.com/blog/health/why-bmi-is-wrong-and-shape-index-is-telling-the-truth/
according to this - my "new" BMI is higher than my actual BMI...so tell me how its a better measurement4 -
mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
If by measurements you mean caliper measurements done by someone who knows what they are doing? Then probably, but measurements themselves aren't particularly accurate.
I also think you and I have a different definition of what it means to be accurate. Individual BMI isn't meant to be a point estimate of someone's body fat percentage, it's meant as an estimate to see what category they fall into and their risks of having an unhealthy body fat percentage based on that category. If people come to MFP with a BMI of 35, it's pretty likely they are indeed obese. As for how can something with such a wide range be accurate, you do realize what it is trying to estimate right? The range of healthy body fat percentages is also wide (14% to 31% for women and 6% to 22% for men), in order to include them all there would also likely be a wide weight range. You're really asking how can such a wide range of weight be healthy and that is not a question for BMI. (Aside from that, statistical accuracy doesn't care about what you think about interval widths, if such a wide interval is accurate for a sample, it's likely mathematically accurate for the population, whether you like how the math works or not).
18.5 is on the verge of underweight for anyone, for someone like him who regularly cycles, it's likely underweight, meaning he likely has a very low body fat percentage (especially since he is a man and likely has a lower body fat percentage than a woman at that weight). How will BMI affect his performance? It won't, but having a lower body fat percentage and trying to lose weight will, which is what BMI is estimating. If you are active and have a low BF%, you're just sacrificing muscle by losing weight, and at his height/weight, that's likely what he's doing. He's 5'9" and 66 kilos as a man, with an FTP of 220, he likely won't gain much by dieting. I say this as a 175cm (5'9") 56 kg (125lb) woman who has been this weight most of my adult life and is also an avid cyclist.
So would you consider caliper measurements done by someone who knows what they're doing to be less accurate than BMI or more?
I'm not sure what you mean in the first few sentences of the 2nd paragraph. Is BMI meant to determine body fat or not?
I agree with you about extreme BMI numbers being "likely" to correlate with obesity, but that can still be better understood by talking about the persons body composition rather than blindly applying a number and therefore a category to them.
I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
You said originally that his BMI will probably negatively affect his performance. Now you say it won't......
Why would having a lower body fat % negatively affect his performance if he lowers that percentage further? He's specifically interested in climbing hills, where a good power to weight ratio is essential. If that fat isn't assisting his power up the hills then it is hindering his power/weight ratio and slowing him down. I won't comment on whether thats a healthy choice, but I'm not sure how its possible to claim that it will negatively affect his performance.
Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Sorry, English isn't my native language so perhaps the language in my post was confusing. Yes, I think caliper measurements done by a "professional" are probably more accurate at assessing BF% than BMI (but I also don't know whether this is true, I have never looked up the study of accuracy of calipers).
BMI, itself, the number, does nothing more than put you into a category, it's the categories which are useful. I do not think BMI, itself, estimates BF% as a point estimate (by point estimate I mean it is not accurate to say a BMI of X equals X% bodyfat, point estimates are never accurate and no statistician would claim such), BMI can, however, make an estimate of whether one is over- or underfat.I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
I say likely because that is how statistics work. BMI is a statistical estimate. It does nothing more than give "likelihoods" and those likelihoods vary with different lifestyle factors (because the underlying population changes, if you want to know the mathematical reason). If we trust BMI then we can only say likelihood because that is all it tells us: likelihoods and risks.
18.5 is the cutoff point for a healthy BMI, taken from the whole population, with no other information, one could only say he was likely on the verge of underweight (because BMI is a likelihood estimation). If we know that he is an active cyclist, the underlying population changes. We are now not looking at BMI for the average population, we are looking at BMI for active cyclists. This distribution will look different. In this distribution, the cutoff BMI for being underfat will likely be higher.
As for BMI negatively affecting his performance, I must have worded it improperly or you misunderstood what I meant, I think having a low BF% and trying to lose weight will negatively affect his performance. I do not think BMI, itself, will negatively affect his performance, it is nothing more than an inferential statistic. If he has a low BF%, it will be hard for him to lose any significant amount of weight without also losing a lot of muscle. If he has a BF% of 20, then he can surely go for it and probably gain some power out of it. However, his w/kg is probably equivalent to a cat 4 racer, he could gain a lot more from decent training before he could gain power by losing weight. He isn't at the point yet where he can only gain power by dropping weight.Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Because I'm a cyclist at his desired weight/height, so I know how it affects at least my own performance. I also want to point out that I am not one of those MFPers who thinks anyone under a BMI of 20 is anorexic, as many people here seem to think.3 -
deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
do you understand statistics at all and standard deviations? 25% of the population will fit into typically 1 standard deviation of the avg population - which is why they pick that range
I do understand statistics. Do you understand the art of reading a post properly and understanding it?
I'm talking about giving specific advice to individuals based on their personal circumstances. It's foolish to apply an average to an individual. Imagine what the world would be like if everyone actually had 2.4 children......
maybe that is something to take up with your medical professional then - because i know my doctor doesn't just give me advice based on BMI - she considers results of body fat assessment (done via a dexa scan and also bodpod); as well as food intake - and if she did, she wouldn't be my doctor much longer
BMI is a statistical tool that can provide initial assessment to see whether an individual potentially falls into an increased risk category for health issues (either from being under or over weight).
wow these replies are coming through quick, I'll try my best to keep up!
It would seem you and I are in agreement then, BMI isn't that much of a useful tool. You need other means of testing to understand the bigger picture.
I don't think anyone is arguing anything other than that. I certainly wouldn't, as that's not what BMI was intended for other than as an initial assessment. However, most people in these forums don't provide us with the results of their full workup at the their last doctor's visit so all we have to make an assessment are height, weight age and stated activity level.
Also, BMI, itself, isn't much of a useful tool, but it is a useful tool to make an initial assessment. It's also useful for making recommendations when you have no better information to go on.
That's a really interesting point. In my experience in reading these forums it tends to be the people replying who say "whats your height and weight, we can work out your BMI" .....rather than saying "tell us some more useful information so that we can properly help you".
But if it isnt that useful then why use it as an initial assessment? Why not get straight in to the details rather than starting to give advice based on some assumption gained from a tool that isnt useful, as you said
because very few people on the forum likely have immediate access to a facility where body fat or VO2Max or BMR etc - can be assessed - so asking for BMI is an initial look-see and then further recommendations can be made
There are plenty of examples of what I've said, you will come across them pretty quickly. I can barely keep up with the speed of these comments, let alone search the forum for all past threads I've read too.
My point still remains that the "initial look see" can still be wrong, so it seems useless to start with it at all.
It seems we have probably reached the point where we have to agree to disagree. Hopefully this link sums up some of my thoughts (about BMI, not shape index, I don't know anything about that)
https://shapescale.com/blog/health/why-bmi-is-wrong-and-shape-index-is-telling-the-truth/
according to this - my "new" BMI is higher than my actual BMI...so tell me how its a better measurement
I'd encourage you, again, to read my post properly. I clearly stated that the information on that site summed up my thoughts on why BMI was such a limited tool, and was not a reflection of my thoughts on shape index, of which I have no knowledge1 -
deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
do you understand statistics at all and standard deviations? 25% of the population will fit into typically 1 standard deviation of the avg population - which is why they pick that range
I do understand statistics. Do you understand the art of reading a post properly and understanding it?
I'm talking about giving specific advice to individuals based on their personal circumstances. It's foolish to apply an average to an individual. Imagine what the world would be like if everyone actually had 2.4 children......
maybe that is something to take up with your medical professional then - because i know my doctor doesn't just give me advice based on BMI - she considers results of body fat assessment (done via a dexa scan and also bodpod); as well as food intake - and if she did, she wouldn't be my doctor much longer
BMI is a statistical tool that can provide initial assessment to see whether an individual potentially falls into an increased risk category for health issues (either from being under or over weight).
wow these replies are coming through quick, I'll try my best to keep up!
It would seem you and I are in agreement then, BMI isn't that much of a useful tool. You need other means of testing to understand the bigger picture.
I don't think anyone is arguing anything other than that. I certainly wouldn't, as that's not what BMI was intended for other than as an initial assessment. However, most people in these forums don't provide us with the results of their full workup at the their last doctor's visit so all we have to make an assessment are height, weight age and stated activity level.
Also, BMI, itself, isn't much of a useful tool, but it is a useful tool to make an initial assessment. It's also useful for making recommendations when you have no better information to go on.
That's a really interesting point. In my experience in reading these forums it tends to be the people replying who say "whats your height and weight, we can work out your BMI" .....rather than saying "tell us some more useful information so that we can properly help you".
But if it isnt that useful then why use it as an initial assessment? Why not get straight in to the details rather than starting to give advice based on some assumption gained from a tool that isnt useful, as you said
because very few people on the forum likely have immediate access to a facility where body fat or VO2Max or BMR etc - can be assessed - so asking for BMI is an initial look-see and then further recommendations can be made
There are plenty of examples of what I've said, you will come across them pretty quickly. I can barely keep up with the speed of these comments, let alone search the forum for all past threads I've read too.
My point still remains that the "initial look see" can still be wrong, so it seems useless to start with it at all.
It seems we have probably reached the point where we have to agree to disagree. Hopefully this link sums up some of my thoughts (about BMI, not shape index, I don't know anything about that)
https://shapescale.com/blog/health/why-bmi-is-wrong-and-shape-index-is-telling-the-truth/
according to this - my "new" BMI is higher than my actual BMI...so tell me how its a better measurement
I've no expertise in this but a study published in the Journal of Translational Medicine concluded it was a "much better indicator of mortality risk". Maybe that's a good place to start1 -
If my bf% is 22 but my BMI is 25 I think it's obvious I don't need to concern myself with what category that places me in but for the most part it's a decent guide for non athletes.5
-
mattrus1989 wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
do you understand statistics at all and standard deviations? 25% of the population will fit into typically 1 standard deviation of the avg population - which is why they pick that range
I do understand statistics. Do you understand the art of reading a post properly and understanding it?
I'm talking about giving specific advice to individuals based on their personal circumstances. It's foolish to apply an average to an individual. Imagine what the world would be like if everyone actually had 2.4 children......
maybe that is something to take up with your medical professional then - because i know my doctor doesn't just give me advice based on BMI - she considers results of body fat assessment (done via a dexa scan and also bodpod); as well as food intake - and if she did, she wouldn't be my doctor much longer
BMI is a statistical tool that can provide initial assessment to see whether an individual potentially falls into an increased risk category for health issues (either from being under or over weight).
wow these replies are coming through quick, I'll try my best to keep up!
It would seem you and I are in agreement then, BMI isn't that much of a useful tool. You need other means of testing to understand the bigger picture.
I don't think anyone is arguing anything other than that. I certainly wouldn't, as that's not what BMI was intended for other than as an initial assessment. However, most people in these forums don't provide us with the results of their full workup at the their last doctor's visit so all we have to make an assessment are height, weight age and stated activity level.
Also, BMI, itself, isn't much of a useful tool, but it is a useful tool to make an initial assessment. It's also useful for making recommendations when you have no better information to go on.
That's a really interesting point. In my experience in reading these forums it tends to be the people replying who say "whats your height and weight, we can work out your BMI" .....rather than saying "tell us some more useful information so that we can properly help you".
But if it isnt that useful then why use it as an initial assessment? Why not get straight in to the details rather than starting to give advice based on some assumption gained from a tool that isnt useful, as you said
Maybe you misunderstood what I meant: BMI is useful...as an initial assessment, it is not useful for much else, nor was it intended to be. We use it as an initial assessment because other tests are costly and/or time consuming. Why do a costly DEXA scan of moderately active 25 year-old who is 180 cm and 70 kg? (Keep in mind, also, that BMI was created at a time before things like DEXA scans, when there were not a lot of reliable ways to measure BF%).
I don't think it should be thrown away all together, we need some "quick and dirty" way to identify cases which are worth looking into more from a health perspective. It's wasteful to do unnecessary tests. I also hate that people on this website act like the fact that BMI is not accurate for bodybuilders and Lance Armstrong means it is not accurate for them either. Sorry, sedentary, middle-aged person with a BMI of 31, your BMI says you are overweight because you probably are, you are not a special-snowflake athlete.11 -
mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
If by measurements you mean caliper measurements done by someone who knows what they are doing? Then probably, but measurements themselves aren't particularly accurate.
I also think you and I have a different definition of what it means to be accurate. Individual BMI isn't meant to be a point estimate of someone's body fat percentage, it's meant as an estimate to see what category they fall into and their risks of having an unhealthy body fat percentage based on that category. If people come to MFP with a BMI of 35, it's pretty likely they are indeed obese. As for how can something with such a wide range be accurate, you do realize what it is trying to estimate right? The range of healthy body fat percentages is also wide (14% to 31% for women and 6% to 22% for men), in order to include them all there would also likely be a wide weight range. You're really asking how can such a wide range of weight be healthy and that is not a question for BMI. (Aside from that, statistical accuracy doesn't care about what you think about interval widths, if such a wide interval is accurate for a sample, it's likely mathematically accurate for the population, whether you like how the math works or not).
18.5 is on the verge of underweight for anyone, for someone like him who regularly cycles, it's likely underweight, meaning he likely has a very low body fat percentage (especially since he is a man and likely has a lower body fat percentage than a woman at that weight). How will BMI affect his performance? It won't, but having a lower body fat percentage and trying to lose weight will, which is what BMI is estimating. If you are active and have a low BF%, you're just sacrificing muscle by losing weight, and at his height/weight, that's likely what he's doing. He's 5'9" and 66 kilos as a man, with an FTP of 220, he likely won't gain much by dieting. I say this as a 175cm (5'9") 56 kg (125lb) woman who has been this weight most of my adult life and is also an avid cyclist.
So would you consider caliper measurements done by someone who knows what they're doing to be less accurate than BMI or more?
I'm not sure what you mean in the first few sentences of the 2nd paragraph. Is BMI meant to determine body fat or not?
I agree with you about extreme BMI numbers being "likely" to correlate with obesity, but that can still be better understood by talking about the persons body composition rather than blindly applying a number and therefore a category to them.
I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
You said originally that his BMI will probably negatively affect his performance. Now you say it won't......
Why would having a lower body fat % negatively affect his performance if he lowers that percentage further? He's specifically interested in climbing hills, where a good power to weight ratio is essential. If that fat isn't assisting his power up the hills then it is hindering his power/weight ratio and slowing him down. I won't comment on whether thats a healthy choice, but I'm not sure how its possible to claim that it will negatively affect his performance.
Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Sorry, English isn't my native language so perhaps the language in my post was confusing. Yes, I think caliper measurements done by a "professional" are probably more accurate at assessing BF% than BMI (but I also don't know whether this is true, I have never looked up the study of accuracy of calipers).
BMI, itself, the number, does nothing more than put you into a category, it's the categories which are useful. I do not think BMI, itself, estimates BF% as a point estimate (by point estimate I mean it is not accurate to say a BMI of X equals X% bodyfat, point estimates are never accurate and no statistician would claim such), BMI can, however, make an estimate of whether one is over- or underfat.I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
I say likely because that is how statistics work. BMI is a statistical estimate. It does nothing more than give "likelihoods" and those likelihoods vary with different lifestyle factors (because the underlying population changes, if you want to know the mathematical reason). If we trust BMI then we can only say likelihood because that is all it tells us: likelihoods and risks.
18.5 is the cutoff point for a healthy BMI, taken from the whole population, with no other information, one could only say he was likely on the verge of underweight (because BMI is a likelihood estimation). If we know that he is an active cyclist, the underlying population changes. We are now not looking at BMI for the average population, we are looking at BMI for active cyclists. This distribution will look different. In this distribution, the cutoff BMI for being underfat will likely be higher.
As for BMI negatively affecting his performance, I must have worded it improperly or you misunderstood what I meant, I think having a low BF% and trying to lose weight will negatively affect his performance. I do not think BMI, itself, will negatively affect his performance, it is nothing more than an inferential statistic. If he has a low BF%, it will be hard for him to lose any significant amount of weight without also losing a lot of muscle. If he has a BF% of 20, then he can surely go for it and probably gain some power out of it. However, his w/kg is probably equivalent to a cat 4 racer, he could gain a lot more from decent training before he could gain power by losing weight. He isn't at the point yet where he can only gain power by dropping weight.Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Because I'm a cyclist at his desired weight/height, so I know how it affects at least my own performance. I also want to point out that I am not one of those MFPers who thinks anyone under a BMI of 20 is anorexic, as many people here seem to think.
You make a good argument, thanks.
I'm no expert in caliper measurements either, but I think it would be fair to say that body composition and fat percentage can be determined much more clearly than the BMI scale.
Your points about population changes is an interesting one, of which you no doubt have more knowledge than me. However, to me at least, its a confusing message. I thought that BMI was a universally recognised scale? Surely the BF% (which BMI claims to calculate) is healthy or unhealthy for any person, regardless of activity? Surely the official BMI numbers and thresholds dont change depending on your activity levels? Maybe I'm wrong but it seems confusing.
For the last part, I totally agree. If he can lose BF then it can still be beneficial to his climbing. That doesn't mean its beneficial to his overall health and it doesnt mean it would be easy to do. And yes, his power needs a lot more work than his weight.1 -
mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
If by measurements you mean caliper measurements done by someone who knows what they are doing? Then probably, but measurements themselves aren't particularly accurate.
I also think you and I have a different definition of what it means to be accurate. Individual BMI isn't meant to be a point estimate of someone's body fat percentage, it's meant as an estimate to see what category they fall into and their risks of having an unhealthy body fat percentage based on that category. If people come to MFP with a BMI of 35, it's pretty likely they are indeed obese. As for how can something with such a wide range be accurate, you do realize what it is trying to estimate right? The range of healthy body fat percentages is also wide (14% to 31% for women and 6% to 22% for men), in order to include them all there would also likely be a wide weight range. You're really asking how can such a wide range of weight be healthy and that is not a question for BMI. (Aside from that, statistical accuracy doesn't care about what you think about interval widths, if such a wide interval is accurate for a sample, it's likely mathematically accurate for the population, whether you like how the math works or not).
18.5 is on the verge of underweight for anyone, for someone like him who regularly cycles, it's likely underweight, meaning he likely has a very low body fat percentage (especially since he is a man and likely has a lower body fat percentage than a woman at that weight). How will BMI affect his performance? It won't, but having a lower body fat percentage and trying to lose weight will, which is what BMI is estimating. If you are active and have a low BF%, you're just sacrificing muscle by losing weight, and at his height/weight, that's likely what he's doing. He's 5'9" and 66 kilos as a man, with an FTP of 220, he likely won't gain much by dieting. I say this as a 175cm (5'9") 56 kg (125lb) woman who has been this weight most of my adult life and is also an avid cyclist.
So would you consider caliper measurements done by someone who knows what they're doing to be less accurate than BMI or more?
I'm not sure what you mean in the first few sentences of the 2nd paragraph. Is BMI meant to determine body fat or not?
I agree with you about extreme BMI numbers being "likely" to correlate with obesity, but that can still be better understood by talking about the persons body composition rather than blindly applying a number and therefore a category to them.
I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
You said originally that his BMI will probably negatively affect his performance. Now you say it won't......
Why would having a lower body fat % negatively affect his performance if he lowers that percentage further? He's specifically interested in climbing hills, where a good power to weight ratio is essential. If that fat isn't assisting his power up the hills then it is hindering his power/weight ratio and slowing him down. I won't comment on whether thats a healthy choice, but I'm not sure how its possible to claim that it will negatively affect his performance.
Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Sorry, English isn't my native language so perhaps the language in my post was confusing. Yes, I think caliper measurements done by a "professional" are probably more accurate at assessing BF% than BMI (but I also don't know whether this is true, I have never looked up the study of accuracy of calipers).
BMI, itself, the number, does nothing more than put you into a category, it's the categories which are useful. I do not think BMI, itself, estimates BF% as a point estimate (by point estimate I mean it is not accurate to say a BMI of X equals X% bodyfat, point estimates are never accurate and no statistician would claim such), BMI can, however, make an estimate of whether one is over- or underfat.I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
I say likely because that is how statistics work. BMI is a statistical estimate. It does nothing more than give "likelihoods" and those likelihoods vary with different lifestyle factors (because the underlying population changes, if you want to know the mathematical reason). If we trust BMI then we can only say likelihood because that is all it tells us: likelihoods and risks.
18.5 is the cutoff point for a healthy BMI, taken from the whole population, with no other information, one could only say he was likely on the verge of underweight (because BMI is a likelihood estimation). If we know that he is an active cyclist, the underlying population changes. We are now not looking at BMI for the average population, we are looking at BMI for active cyclists. This distribution will look different. In this distribution, the cutoff BMI for being underfat will likely be higher.
As for BMI negatively affecting his performance, I must have worded it improperly or you misunderstood what I meant, I think having a low BF% and trying to lose weight will negatively affect his performance. I do not think BMI, itself, will negatively affect his performance, it is nothing more than an inferential statistic. If he has a low BF%, it will be hard for him to lose any significant amount of weight without also losing a lot of muscle. If he has a BF% of 20, then he can surely go for it and probably gain some power out of it. However, his w/kg is probably equivalent to a cat 4 racer, he could gain a lot more from decent training before he could gain power by losing weight. He isn't at the point yet where he can only gain power by dropping weight.Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Because I'm a cyclist at his desired weight/height, so I know how it affects at least my own performance. I also want to point out that I am not one of those MFPers who thinks anyone under a BMI of 20 is anorexic, as many people here seem to think.
You make a good argument, thanks.
I'm no expert in caliper measurements either, but I think it would be fair to say that body composition and fat percentage can be determined much more clearly than the BMI scale.
Your points about population changes is an interesting one, of which you no doubt have more knowledge than me. However, to me at least, its a confusing message. I thought that BMI was a universally recognised scale? Surely the BF% (which BMI claims to calculate) is healthy or unhealthy for any person, regardless of activity? Surely the official BMI numbers and thresholds dont change depending on your activity levels? Maybe I'm wrong but it seems confusing.
For the last part, I totally agree. If he can lose BF then it can still be beneficial to his climbing. That doesn't mean its beneficial to his overall health and it doesnt mean it would be easy to do. And yes, his power needs a lot more work than his weight.
BMI doesn't calculate BF% - which is exactly the issue i thought you were arguing? so now i'm just confused.7 -
mattrus1989 wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
do you understand statistics at all and standard deviations? 25% of the population will fit into typically 1 standard deviation of the avg population - which is why they pick that range
I do understand statistics. Do you understand the art of reading a post properly and understanding it?
I'm talking about giving specific advice to individuals based on their personal circumstances. It's foolish to apply an average to an individual. Imagine what the world would be like if everyone actually had 2.4 children......
maybe that is something to take up with your medical professional then - because i know my doctor doesn't just give me advice based on BMI - she considers results of body fat assessment (done via a dexa scan and also bodpod); as well as food intake - and if she did, she wouldn't be my doctor much longer
BMI is a statistical tool that can provide initial assessment to see whether an individual potentially falls into an increased risk category for health issues (either from being under or over weight).
wow these replies are coming through quick, I'll try my best to keep up!
It would seem you and I are in agreement then, BMI isn't that much of a useful tool. You need other means of testing to understand the bigger picture.
I don't think anyone is arguing anything other than that. I certainly wouldn't, as that's not what BMI was intended for other than as an initial assessment. However, most people in these forums don't provide us with the results of their full workup at the their last doctor's visit so all we have to make an assessment are height, weight age and stated activity level.
Also, BMI, itself, isn't much of a useful tool, but it is a useful tool to make an initial assessment. It's also useful for making recommendations when you have no better information to go on.
That's a really interesting point. In my experience in reading these forums it tends to be the people replying who say "whats your height and weight, we can work out your BMI" .....rather than saying "tell us some more useful information so that we can properly help you".
But if it isnt that useful then why use it as an initial assessment? Why not get straight in to the details rather than starting to give advice based on some assumption gained from a tool that isnt useful, as you said
Maybe you misunderstood what I meant: BMI is useful...as an initial assessment, it is not useful for much else, nor was it intended to be. We use it as an initial assessment because other tests are costly and/or time consuming. Why do a costly DEXA scan of moderately active 25 year-old who is 180 cm and 70 kg? (Keep in mind, also, that BMI was created at a time before things like DEXA scans, when there were not a lot of reliable ways to measure BF%).
I don't think it should be thrown away all together, we need some "quick and dirty" way to identify cases which are worth looking into more from a health perspective. It's wasteful to do unnecessary tests. I also hate that people on this website act like the fact that BMI is not accurate for bodybuilders and Lance Armstrong means it is not accurate for them either. Sorry, sedentary, middle-aged person with a BMI of 31, your BMI says you are overweight because you probably are, you are not a special-snowflake athlete.
I agree with you in the most part. You definitely hit the nail on the head with "quick and dirty" but also when you suggested that BMI comes from a time long past. You'd think we could move on to slightly more modern and accurate ways of assessment.
I agree about using extreme examples to apply it to other people too. But does falling in the middle of the "healthy" grading mean you can relax about your weight and not worry about health problems? No, I dont think it does1 -
mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
do you understand statistics at all and standard deviations? 25% of the population will fit into typically 1 standard deviation of the avg population - which is why they pick that range
I do understand statistics. Do you understand the art of reading a post properly and understanding it?
I'm talking about giving specific advice to individuals based on their personal circumstances. It's foolish to apply an average to an individual. Imagine what the world would be like if everyone actually had 2.4 children......
maybe that is something to take up with your medical professional then - because i know my doctor doesn't just give me advice based on BMI - she considers results of body fat assessment (done via a dexa scan and also bodpod); as well as food intake - and if she did, she wouldn't be my doctor much longer
BMI is a statistical tool that can provide initial assessment to see whether an individual potentially falls into an increased risk category for health issues (either from being under or over weight).
wow these replies are coming through quick, I'll try my best to keep up!
It would seem you and I are in agreement then, BMI isn't that much of a useful tool. You need other means of testing to understand the bigger picture.
I don't think anyone is arguing anything other than that. I certainly wouldn't, as that's not what BMI was intended for other than as an initial assessment. However, most people in these forums don't provide us with the results of their full workup at the their last doctor's visit so all we have to make an assessment are height, weight age and stated activity level.
Also, BMI, itself, isn't much of a useful tool, but it is a useful tool to make an initial assessment. It's also useful for making recommendations when you have no better information to go on.
That's a really interesting point. In my experience in reading these forums it tends to be the people replying who say "whats your height and weight, we can work out your BMI" .....rather than saying "tell us some more useful information so that we can properly help you".
But if it isnt that useful then why use it as an initial assessment? Why not get straight in to the details rather than starting to give advice based on some assumption gained from a tool that isnt useful, as you said
because very few people on the forum likely have immediate access to a facility where body fat or VO2Max or BMR etc - can be assessed - so asking for BMI is an initial look-see and then further recommendations can be made
There are plenty of examples of what I've said, you will come across them pretty quickly. I can barely keep up with the speed of these comments, let alone search the forum for all past threads I've read too.
My point still remains that the "initial look see" can still be wrong, so it seems useless to start with it at all.
It seems we have probably reached the point where we have to agree to disagree. Hopefully this link sums up some of my thoughts (about BMI, not shape index, I don't know anything about that)
https://shapescale.com/blog/health/why-bmi-is-wrong-and-shape-index-is-telling-the-truth/
according to this - my "new" BMI is higher than my actual BMI...so tell me how its a better measurement
I'd encourage you, again, to read my post properly. I clearly stated that the information on that site summed up my thoughts on why BMI was such a limited tool, and was not a reflection of my thoughts on shape index, of which I have no knowledge
i read your post - however, when they erroneously say in said same post that this alternate tool is a better measurement and but there is no scientific validity mentioned - then the entire information in the post is IMHO questionable - since that is the basis that any researcher or student would evaluate the information contained within5 -
TavistockToad wrote: »mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
If by measurements you mean caliper measurements done by someone who knows what they are doing? Then probably, but measurements themselves aren't particularly accurate.
I also think you and I have a different definition of what it means to be accurate. Individual BMI isn't meant to be a point estimate of someone's body fat percentage, it's meant as an estimate to see what category they fall into and their risks of having an unhealthy body fat percentage based on that category. If people come to MFP with a BMI of 35, it's pretty likely they are indeed obese. As for how can something with such a wide range be accurate, you do realize what it is trying to estimate right? The range of healthy body fat percentages is also wide (14% to 31% for women and 6% to 22% for men), in order to include them all there would also likely be a wide weight range. You're really asking how can such a wide range of weight be healthy and that is not a question for BMI. (Aside from that, statistical accuracy doesn't care about what you think about interval widths, if such a wide interval is accurate for a sample, it's likely mathematically accurate for the population, whether you like how the math works or not).
18.5 is on the verge of underweight for anyone, for someone like him who regularly cycles, it's likely underweight, meaning he likely has a very low body fat percentage (especially since he is a man and likely has a lower body fat percentage than a woman at that weight). How will BMI affect his performance? It won't, but having a lower body fat percentage and trying to lose weight will, which is what BMI is estimating. If you are active and have a low BF%, you're just sacrificing muscle by losing weight, and at his height/weight, that's likely what he's doing. He's 5'9" and 66 kilos as a man, with an FTP of 220, he likely won't gain much by dieting. I say this as a 175cm (5'9") 56 kg (125lb) woman who has been this weight most of my adult life and is also an avid cyclist.
So would you consider caliper measurements done by someone who knows what they're doing to be less accurate than BMI or more?
I'm not sure what you mean in the first few sentences of the 2nd paragraph. Is BMI meant to determine body fat or not?
I agree with you about extreme BMI numbers being "likely" to correlate with obesity, but that can still be better understood by talking about the persons body composition rather than blindly applying a number and therefore a category to them.
I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
You said originally that his BMI will probably negatively affect his performance. Now you say it won't......
Why would having a lower body fat % negatively affect his performance if he lowers that percentage further? He's specifically interested in climbing hills, where a good power to weight ratio is essential. If that fat isn't assisting his power up the hills then it is hindering his power/weight ratio and slowing him down. I won't comment on whether thats a healthy choice, but I'm not sure how its possible to claim that it will negatively affect his performance.
Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Sorry, English isn't my native language so perhaps the language in my post was confusing. Yes, I think caliper measurements done by a "professional" are probably more accurate at assessing BF% than BMI (but I also don't know whether this is true, I have never looked up the study of accuracy of calipers).
BMI, itself, the number, does nothing more than put you into a category, it's the categories which are useful. I do not think BMI, itself, estimates BF% as a point estimate (by point estimate I mean it is not accurate to say a BMI of X equals X% bodyfat, point estimates are never accurate and no statistician would claim such), BMI can, however, make an estimate of whether one is over- or underfat.I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
I say likely because that is how statistics work. BMI is a statistical estimate. It does nothing more than give "likelihoods" and those likelihoods vary with different lifestyle factors (because the underlying population changes, if you want to know the mathematical reason). If we trust BMI then we can only say likelihood because that is all it tells us: likelihoods and risks.
18.5 is the cutoff point for a healthy BMI, taken from the whole population, with no other information, one could only say he was likely on the verge of underweight (because BMI is a likelihood estimation). If we know that he is an active cyclist, the underlying population changes. We are now not looking at BMI for the average population, we are looking at BMI for active cyclists. This distribution will look different. In this distribution, the cutoff BMI for being underfat will likely be higher.
As for BMI negatively affecting his performance, I must have worded it improperly or you misunderstood what I meant, I think having a low BF% and trying to lose weight will negatively affect his performance. I do not think BMI, itself, will negatively affect his performance, it is nothing more than an inferential statistic. If he has a low BF%, it will be hard for him to lose any significant amount of weight without also losing a lot of muscle. If he has a BF% of 20, then he can surely go for it and probably gain some power out of it. However, his w/kg is probably equivalent to a cat 4 racer, he could gain a lot more from decent training before he could gain power by losing weight. He isn't at the point yet where he can only gain power by dropping weight.Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Because I'm a cyclist at his desired weight/height, so I know how it affects at least my own performance. I also want to point out that I am not one of those MFPers who thinks anyone under a BMI of 20 is anorexic, as many people here seem to think.
You make a good argument, thanks.
I'm no expert in caliper measurements either, but I think it would be fair to say that body composition and fat percentage can be determined much more clearly than the BMI scale.
Your points about population changes is an interesting one, of which you no doubt have more knowledge than me. However, to me at least, its a confusing message. I thought that BMI was a universally recognised scale? Surely the BF% (which BMI claims to calculate) is healthy or unhealthy for any person, regardless of activity? Surely the official BMI numbers and thresholds dont change depending on your activity levels? Maybe I'm wrong but it seems confusing.
For the last part, I totally agree. If he can lose BF then it can still be beneficial to his climbing. That doesn't mean its beneficial to his overall health and it doesnt mean it would be easy to do. And yes, his power needs a lot more work than his weight.
BMI doesn't calculate BF% - which is exactly the issue i thought you were arguing? so now i'm just confused.
But it does assess your health and risk of obesity related diseases based on the assumed fat that your body has, does it not? Hence it categorising people as "obese" based purely on their height and weight3 -
also the only article in the Journal of Translational Measurement related to this new measurement was a study on sedentary male university students (N=114) and the study specifically focused on Triacylglycerols, total cholesterol and HDL-cholesterol levels in plasma compared between the 2 measurements0
-
mattrus1989 wrote: »TavistockToad wrote: »mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
If by measurements you mean caliper measurements done by someone who knows what they are doing? Then probably, but measurements themselves aren't particularly accurate.
I also think you and I have a different definition of what it means to be accurate. Individual BMI isn't meant to be a point estimate of someone's body fat percentage, it's meant as an estimate to see what category they fall into and their risks of having an unhealthy body fat percentage based on that category. If people come to MFP with a BMI of 35, it's pretty likely they are indeed obese. As for how can something with such a wide range be accurate, you do realize what it is trying to estimate right? The range of healthy body fat percentages is also wide (14% to 31% for women and 6% to 22% for men), in order to include them all there would also likely be a wide weight range. You're really asking how can such a wide range of weight be healthy and that is not a question for BMI. (Aside from that, statistical accuracy doesn't care about what you think about interval widths, if such a wide interval is accurate for a sample, it's likely mathematically accurate for the population, whether you like how the math works or not).
18.5 is on the verge of underweight for anyone, for someone like him who regularly cycles, it's likely underweight, meaning he likely has a very low body fat percentage (especially since he is a man and likely has a lower body fat percentage than a woman at that weight). How will BMI affect his performance? It won't, but having a lower body fat percentage and trying to lose weight will, which is what BMI is estimating. If you are active and have a low BF%, you're just sacrificing muscle by losing weight, and at his height/weight, that's likely what he's doing. He's 5'9" and 66 kilos as a man, with an FTP of 220, he likely won't gain much by dieting. I say this as a 175cm (5'9") 56 kg (125lb) woman who has been this weight most of my adult life and is also an avid cyclist.
So would you consider caliper measurements done by someone who knows what they're doing to be less accurate than BMI or more?
I'm not sure what you mean in the first few sentences of the 2nd paragraph. Is BMI meant to determine body fat or not?
I agree with you about extreme BMI numbers being "likely" to correlate with obesity, but that can still be better understood by talking about the persons body composition rather than blindly applying a number and therefore a category to them.
I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
You said originally that his BMI will probably negatively affect his performance. Now you say it won't......
Why would having a lower body fat % negatively affect his performance if he lowers that percentage further? He's specifically interested in climbing hills, where a good power to weight ratio is essential. If that fat isn't assisting his power up the hills then it is hindering his power/weight ratio and slowing him down. I won't comment on whether thats a healthy choice, but I'm not sure how its possible to claim that it will negatively affect his performance.
Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Sorry, English isn't my native language so perhaps the language in my post was confusing. Yes, I think caliper measurements done by a "professional" are probably more accurate at assessing BF% than BMI (but I also don't know whether this is true, I have never looked up the study of accuracy of calipers).
BMI, itself, the number, does nothing more than put you into a category, it's the categories which are useful. I do not think BMI, itself, estimates BF% as a point estimate (by point estimate I mean it is not accurate to say a BMI of X equals X% bodyfat, point estimates are never accurate and no statistician would claim such), BMI can, however, make an estimate of whether one is over- or underfat.I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
I say likely because that is how statistics work. BMI is a statistical estimate. It does nothing more than give "likelihoods" and those likelihoods vary with different lifestyle factors (because the underlying population changes, if you want to know the mathematical reason). If we trust BMI then we can only say likelihood because that is all it tells us: likelihoods and risks.
18.5 is the cutoff point for a healthy BMI, taken from the whole population, with no other information, one could only say he was likely on the verge of underweight (because BMI is a likelihood estimation). If we know that he is an active cyclist, the underlying population changes. We are now not looking at BMI for the average population, we are looking at BMI for active cyclists. This distribution will look different. In this distribution, the cutoff BMI for being underfat will likely be higher.
As for BMI negatively affecting his performance, I must have worded it improperly or you misunderstood what I meant, I think having a low BF% and trying to lose weight will negatively affect his performance. I do not think BMI, itself, will negatively affect his performance, it is nothing more than an inferential statistic. If he has a low BF%, it will be hard for him to lose any significant amount of weight without also losing a lot of muscle. If he has a BF% of 20, then he can surely go for it and probably gain some power out of it. However, his w/kg is probably equivalent to a cat 4 racer, he could gain a lot more from decent training before he could gain power by losing weight. He isn't at the point yet where he can only gain power by dropping weight.Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Because I'm a cyclist at his desired weight/height, so I know how it affects at least my own performance. I also want to point out that I am not one of those MFPers who thinks anyone under a BMI of 20 is anorexic, as many people here seem to think.
You make a good argument, thanks.
I'm no expert in caliper measurements either, but I think it would be fair to say that body composition and fat percentage can be determined much more clearly than the BMI scale.
Your points about population changes is an interesting one, of which you no doubt have more knowledge than me. However, to me at least, its a confusing message. I thought that BMI was a universally recognised scale? Surely the BF% (which BMI claims to calculate) is healthy or unhealthy for any person, regardless of activity? Surely the official BMI numbers and thresholds dont change depending on your activity levels? Maybe I'm wrong but it seems confusing.
For the last part, I totally agree. If he can lose BF then it can still be beneficial to his climbing. That doesn't mean its beneficial to his overall health and it doesnt mean it would be easy to do. And yes, his power needs a lot more work than his weight.
BMI doesn't calculate BF% - which is exactly the issue i thought you were arguing? so now i'm just confused.
But it does assess your health and risk of obesity related diseases based on the assumed fat that your body has, does it not? Hence it categorising people as "obese" based purely on their height and weight
is that why you have such an issue with BMI? it calls you fat!? :laugh:6 -
TavistockToad wrote: »mattrus1989 wrote: »TavistockToad wrote: »mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
If by measurements you mean caliper measurements done by someone who knows what they are doing? Then probably, but measurements themselves aren't particularly accurate.
I also think you and I have a different definition of what it means to be accurate. Individual BMI isn't meant to be a point estimate of someone's body fat percentage, it's meant as an estimate to see what category they fall into and their risks of having an unhealthy body fat percentage based on that category. If people come to MFP with a BMI of 35, it's pretty likely they are indeed obese. As for how can something with such a wide range be accurate, you do realize what it is trying to estimate right? The range of healthy body fat percentages is also wide (14% to 31% for women and 6% to 22% for men), in order to include them all there would also likely be a wide weight range. You're really asking how can such a wide range of weight be healthy and that is not a question for BMI. (Aside from that, statistical accuracy doesn't care about what you think about interval widths, if such a wide interval is accurate for a sample, it's likely mathematically accurate for the population, whether you like how the math works or not).
18.5 is on the verge of underweight for anyone, for someone like him who regularly cycles, it's likely underweight, meaning he likely has a very low body fat percentage (especially since he is a man and likely has a lower body fat percentage than a woman at that weight). How will BMI affect his performance? It won't, but having a lower body fat percentage and trying to lose weight will, which is what BMI is estimating. If you are active and have a low BF%, you're just sacrificing muscle by losing weight, and at his height/weight, that's likely what he's doing. He's 5'9" and 66 kilos as a man, with an FTP of 220, he likely won't gain much by dieting. I say this as a 175cm (5'9") 56 kg (125lb) woman who has been this weight most of my adult life and is also an avid cyclist.
So would you consider caliper measurements done by someone who knows what they're doing to be less accurate than BMI or more?
I'm not sure what you mean in the first few sentences of the 2nd paragraph. Is BMI meant to determine body fat or not?
I agree with you about extreme BMI numbers being "likely" to correlate with obesity, but that can still be better understood by talking about the persons body composition rather than blindly applying a number and therefore a category to them.
I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
You said originally that his BMI will probably negatively affect his performance. Now you say it won't......
Why would having a lower body fat % negatively affect his performance if he lowers that percentage further? He's specifically interested in climbing hills, where a good power to weight ratio is essential. If that fat isn't assisting his power up the hills then it is hindering his power/weight ratio and slowing him down. I won't comment on whether thats a healthy choice, but I'm not sure how its possible to claim that it will negatively affect his performance.
Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Sorry, English isn't my native language so perhaps the language in my post was confusing. Yes, I think caliper measurements done by a "professional" are probably more accurate at assessing BF% than BMI (but I also don't know whether this is true, I have never looked up the study of accuracy of calipers).
BMI, itself, the number, does nothing more than put you into a category, it's the categories which are useful. I do not think BMI, itself, estimates BF% as a point estimate (by point estimate I mean it is not accurate to say a BMI of X equals X% bodyfat, point estimates are never accurate and no statistician would claim such), BMI can, however, make an estimate of whether one is over- or underfat.I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
I say likely because that is how statistics work. BMI is a statistical estimate. It does nothing more than give "likelihoods" and those likelihoods vary with different lifestyle factors (because the underlying population changes, if you want to know the mathematical reason). If we trust BMI then we can only say likelihood because that is all it tells us: likelihoods and risks.
18.5 is the cutoff point for a healthy BMI, taken from the whole population, with no other information, one could only say he was likely on the verge of underweight (because BMI is a likelihood estimation). If we know that he is an active cyclist, the underlying population changes. We are now not looking at BMI for the average population, we are looking at BMI for active cyclists. This distribution will look different. In this distribution, the cutoff BMI for being underfat will likely be higher.
As for BMI negatively affecting his performance, I must have worded it improperly or you misunderstood what I meant, I think having a low BF% and trying to lose weight will negatively affect his performance. I do not think BMI, itself, will negatively affect his performance, it is nothing more than an inferential statistic. If he has a low BF%, it will be hard for him to lose any significant amount of weight without also losing a lot of muscle. If he has a BF% of 20, then he can surely go for it and probably gain some power out of it. However, his w/kg is probably equivalent to a cat 4 racer, he could gain a lot more from decent training before he could gain power by losing weight. He isn't at the point yet where he can only gain power by dropping weight.Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Because I'm a cyclist at his desired weight/height, so I know how it affects at least my own performance. I also want to point out that I am not one of those MFPers who thinks anyone under a BMI of 20 is anorexic, as many people here seem to think.
You make a good argument, thanks.
I'm no expert in caliper measurements either, but I think it would be fair to say that body composition and fat percentage can be determined much more clearly than the BMI scale.
Your points about population changes is an interesting one, of which you no doubt have more knowledge than me. However, to me at least, its a confusing message. I thought that BMI was a universally recognised scale? Surely the BF% (which BMI claims to calculate) is healthy or unhealthy for any person, regardless of activity? Surely the official BMI numbers and thresholds dont change depending on your activity levels? Maybe I'm wrong but it seems confusing.
For the last part, I totally agree. If he can lose BF then it can still be beneficial to his climbing. That doesn't mean its beneficial to his overall health and it doesnt mean it would be easy to do. And yes, his power needs a lot more work than his weight.
BMI doesn't calculate BF% - which is exactly the issue i thought you were arguing? so now i'm just confused.
But it does assess your health and risk of obesity related diseases based on the assumed fat that your body has, does it not? Hence it categorising people as "obese" based purely on their height and weight
is that why you have such an issue with BMI? it calls you fat!? :laugh:
I fall in the middle of the healthy scale. Thank god! Now i can sleep at night0 -
mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
If by measurements you mean caliper measurements done by someone who knows what they are doing? Then probably, but measurements themselves aren't particularly accurate.
I also think you and I have a different definition of what it means to be accurate. Individual BMI isn't meant to be a point estimate of someone's body fat percentage, it's meant as an estimate to see what category they fall into and their risks of having an unhealthy body fat percentage based on that category. If people come to MFP with a BMI of 35, it's pretty likely they are indeed obese. As for how can something with such a wide range be accurate, you do realize what it is trying to estimate right? The range of healthy body fat percentages is also wide (14% to 31% for women and 6% to 22% for men), in order to include them all there would also likely be a wide weight range. You're really asking how can such a wide range of weight be healthy and that is not a question for BMI. (Aside from that, statistical accuracy doesn't care about what you think about interval widths, if such a wide interval is accurate for a sample, it's likely mathematically accurate for the population, whether you like how the math works or not).
18.5 is on the verge of underweight for anyone, for someone like him who regularly cycles, it's likely underweight, meaning he likely has a very low body fat percentage (especially since he is a man and likely has a lower body fat percentage than a woman at that weight). How will BMI affect his performance? It won't, but having a lower body fat percentage and trying to lose weight will, which is what BMI is estimating. If you are active and have a low BF%, you're just sacrificing muscle by losing weight, and at his height/weight, that's likely what he's doing. He's 5'9" and 66 kilos as a man, with an FTP of 220, he likely won't gain much by dieting. I say this as a 175cm (5'9") 56 kg (125lb) woman who has been this weight most of my adult life and is also an avid cyclist.
So would you consider caliper measurements done by someone who knows what they're doing to be less accurate than BMI or more?
I'm not sure what you mean in the first few sentences of the 2nd paragraph. Is BMI meant to determine body fat or not?
I agree with you about extreme BMI numbers being "likely" to correlate with obesity, but that can still be better understood by talking about the persons body composition rather than blindly applying a number and therefore a category to them.
I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
You said originally that his BMI will probably negatively affect his performance. Now you say it won't......
Why would having a lower body fat % negatively affect his performance if he lowers that percentage further? He's specifically interested in climbing hills, where a good power to weight ratio is essential. If that fat isn't assisting his power up the hills then it is hindering his power/weight ratio and slowing him down. I won't comment on whether thats a healthy choice, but I'm not sure how its possible to claim that it will negatively affect his performance.
Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Sorry, English isn't my native language so perhaps the language in my post was confusing. Yes, I think caliper measurements done by a "professional" are probably more accurate at assessing BF% than BMI (but I also don't know whether this is true, I have never looked up the study of accuracy of calipers).
BMI, itself, the number, does nothing more than put you into a category, it's the categories which are useful. I do not think BMI, itself, estimates BF% as a point estimate (by point estimate I mean it is not accurate to say a BMI of X equals X% bodyfat, point estimates are never accurate and no statistician would claim such), BMI can, however, make an estimate of whether one is over- or underfat.I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
I say likely because that is how statistics work. BMI is a statistical estimate. It does nothing more than give "likelihoods" and those likelihoods vary with different lifestyle factors (because the underlying population changes, if you want to know the mathematical reason). If we trust BMI then we can only say likelihood because that is all it tells us: likelihoods and risks.
18.5 is the cutoff point for a healthy BMI, taken from the whole population, with no other information, one could only say he was likely on the verge of underweight (because BMI is a likelihood estimation). If we know that he is an active cyclist, the underlying population changes. We are now not looking at BMI for the average population, we are looking at BMI for active cyclists. This distribution will look different. In this distribution, the cutoff BMI for being underfat will likely be higher.
As for BMI negatively affecting his performance, I must have worded it improperly or you misunderstood what I meant, I think having a low BF% and trying to lose weight will negatively affect his performance. I do not think BMI, itself, will negatively affect his performance, it is nothing more than an inferential statistic. If he has a low BF%, it will be hard for him to lose any significant amount of weight without also losing a lot of muscle. If he has a BF% of 20, then he can surely go for it and probably gain some power out of it. However, his w/kg is probably equivalent to a cat 4 racer, he could gain a lot more from decent training before he could gain power by losing weight. He isn't at the point yet where he can only gain power by dropping weight.Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Because I'm a cyclist at his desired weight/height, so I know how it affects at least my own performance. I also want to point out that I am not one of those MFPers who thinks anyone under a BMI of 20 is anorexic, as many people here seem to think.
You make a good argument, thanks.
I'm no expert in caliper measurements either, but I think it would be fair to say that body composition and fat percentage can be determined much more clearly than the BMI scale.
Your points about population changes is an interesting one, of which you no doubt have more knowledge than me. However, to me at least, its a confusing message. I thought that BMI was a universally recognised scale? Surely the BF% (which BMI claims to calculate) is healthy or unhealthy for any person, regardless of activity? Surely the official BMI numbers and thresholds dont change depending on your activity levels? Maybe I'm wrong but it seems confusing.
For the last part, I totally agree. If he can lose BF then it can still be beneficial to his climbing. That doesn't mean its beneficial to his overall health and it doesnt mean it would be easy to do. And yes, his power needs a lot more work than his weight.
I agree that I think this is a point where BMI has been misapplied, it's not meant to estimate body fat percentage, per se. Statisticians hate point estimates because they are almost never accurate. What it is meant to do is estimate whether someone is under- or overfat based on their height and weight. Basically they take a distribution of people and make a range in which x% of people have a healthy body fat. The range changes depending on activity level because the body fat percentage for a certain height/weight will be different depending on activity level, as you have pointed out. So, someone with a BMI of 19 who is lightly active might have a BF% of 20, but someone with a BMI of 19 that is a professional athlete might have a BF% of 14. So if the underlying population changes, in this case to athletes, the BMI at which one will have too little body fat will probably be higher (because muscle is denser than fat, as we all know, thus a higher weight to height ratio for the same BF%). The intervals are then shifted upwards for athletes, downwards for excessively sedentary people.
Long story short: BMI is just a ratio they use that is correlated with BF% but doesn't necessarily estimate it. And in that case, if it is used to estimate BF% itself, it is incorrectly applied.2 -
deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
do you understand statistics at all and standard deviations? 25% of the population will fit into typically 1 standard deviation of the avg population - which is why they pick that range
I do understand statistics. Do you understand the art of reading a post properly and understanding it?
I'm talking about giving specific advice to individuals based on their personal circumstances. It's foolish to apply an average to an individual. Imagine what the world would be like if everyone actually had 2.4 children......
maybe that is something to take up with your medical professional then - because i know my doctor doesn't just give me advice based on BMI - she considers results of body fat assessment (done via a dexa scan and also bodpod); as well as food intake - and if she did, she wouldn't be my doctor much longer
BMI is a statistical tool that can provide initial assessment to see whether an individual potentially falls into an increased risk category for health issues (either from being under or over weight).
wow these replies are coming through quick, I'll try my best to keep up!
It would seem you and I are in agreement then, BMI isn't that much of a useful tool. You need other means of testing to understand the bigger picture.
I don't think anyone is arguing anything other than that. I certainly wouldn't, as that's not what BMI was intended for other than as an initial assessment. However, most people in these forums don't provide us with the results of their full workup at the their last doctor's visit so all we have to make an assessment are height, weight age and stated activity level.
Also, BMI, itself, isn't much of a useful tool, but it is a useful tool to make an initial assessment. It's also useful for making recommendations when you have no better information to go on.
That's a really interesting point. In my experience in reading these forums it tends to be the people replying who say "whats your height and weight, we can work out your BMI" .....rather than saying "tell us some more useful information so that we can properly help you".
But if it isnt that useful then why use it as an initial assessment? Why not get straight in to the details rather than starting to give advice based on some assumption gained from a tool that isnt useful, as you said
because very few people on the forum likely have immediate access to a facility where body fat or VO2Max or BMR etc - can be assessed - so asking for BMI is an initial look-see and then further recommendations can be made
There are plenty of examples of what I've said, you will come across them pretty quickly. I can barely keep up with the speed of these comments, let alone search the forum for all past threads I've read too.
My point still remains that the "initial look see" can still be wrong, so it seems useless to start with it at all.
It seems we have probably reached the point where we have to agree to disagree. Hopefully this link sums up some of my thoughts (about BMI, not shape index, I don't know anything about that)
https://shapescale.com/blog/health/why-bmi-is-wrong-and-shape-index-is-telling-the-truth/
according to this - my "new" BMI is higher than my actual BMI...so tell me how its a better measurement
I'd encourage you, again, to read my post properly. I clearly stated that the information on that site summed up my thoughts on why BMI was such a limited tool, and was not a reflection of my thoughts on shape index, of which I have no knowledge
i read your post - however, when they erroneously say in said same post that this alternate tool is a better measurement and but there is no scientific validity mentioned - then the entire information in the post is IMHO questionable - since that is the basis that any researcher or student would evaluate the information contained within
Well I was quite clear about why I was posting the article.....
The shortcomings of the alternate tool has no reflection on the limitations of the BMI. Those limitations are true and present whether there's better alternatives or not.
0 -
mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
If by measurements you mean caliper measurements done by someone who knows what they are doing? Then probably, but measurements themselves aren't particularly accurate.
I also think you and I have a different definition of what it means to be accurate. Individual BMI isn't meant to be a point estimate of someone's body fat percentage, it's meant as an estimate to see what category they fall into and their risks of having an unhealthy body fat percentage based on that category. If people come to MFP with a BMI of 35, it's pretty likely they are indeed obese. As for how can something with such a wide range be accurate, you do realize what it is trying to estimate right? The range of healthy body fat percentages is also wide (14% to 31% for women and 6% to 22% for men), in order to include them all there would also likely be a wide weight range. You're really asking how can such a wide range of weight be healthy and that is not a question for BMI. (Aside from that, statistical accuracy doesn't care about what you think about interval widths, if such a wide interval is accurate for a sample, it's likely mathematically accurate for the population, whether you like how the math works or not).
18.5 is on the verge of underweight for anyone, for someone like him who regularly cycles, it's likely underweight, meaning he likely has a very low body fat percentage (especially since he is a man and likely has a lower body fat percentage than a woman at that weight). How will BMI affect his performance? It won't, but having a lower body fat percentage and trying to lose weight will, which is what BMI is estimating. If you are active and have a low BF%, you're just sacrificing muscle by losing weight, and at his height/weight, that's likely what he's doing. He's 5'9" and 66 kilos as a man, with an FTP of 220, he likely won't gain much by dieting. I say this as a 175cm (5'9") 56 kg (125lb) woman who has been this weight most of my adult life and is also an avid cyclist.
So would you consider caliper measurements done by someone who knows what they're doing to be less accurate than BMI or more?
I'm not sure what you mean in the first few sentences of the 2nd paragraph. Is BMI meant to determine body fat or not?
I agree with you about extreme BMI numbers being "likely" to correlate with obesity, but that can still be better understood by talking about the persons body composition rather than blindly applying a number and therefore a category to them.
I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
You said originally that his BMI will probably negatively affect his performance. Now you say it won't......
Why would having a lower body fat % negatively affect his performance if he lowers that percentage further? He's specifically interested in climbing hills, where a good power to weight ratio is essential. If that fat isn't assisting his power up the hills then it is hindering his power/weight ratio and slowing him down. I won't comment on whether thats a healthy choice, but I'm not sure how its possible to claim that it will negatively affect his performance.
Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Sorry, English isn't my native language so perhaps the language in my post was confusing. Yes, I think caliper measurements done by a "professional" are probably more accurate at assessing BF% than BMI (but I also don't know whether this is true, I have never looked up the study of accuracy of calipers).
BMI, itself, the number, does nothing more than put you into a category, it's the categories which are useful. I do not think BMI, itself, estimates BF% as a point estimate (by point estimate I mean it is not accurate to say a BMI of X equals X% bodyfat, point estimates are never accurate and no statistician would claim such), BMI can, however, make an estimate of whether one is over- or underfat.I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
I say likely because that is how statistics work. BMI is a statistical estimate. It does nothing more than give "likelihoods" and those likelihoods vary with different lifestyle factors (because the underlying population changes, if you want to know the mathematical reason). If we trust BMI then we can only say likelihood because that is all it tells us: likelihoods and risks.
18.5 is the cutoff point for a healthy BMI, taken from the whole population, with no other information, one could only say he was likely on the verge of underweight (because BMI is a likelihood estimation). If we know that he is an active cyclist, the underlying population changes. We are now not looking at BMI for the average population, we are looking at BMI for active cyclists. This distribution will look different. In this distribution, the cutoff BMI for being underfat will likely be higher.
As for BMI negatively affecting his performance, I must have worded it improperly or you misunderstood what I meant, I think having a low BF% and trying to lose weight will negatively affect his performance. I do not think BMI, itself, will negatively affect his performance, it is nothing more than an inferential statistic. If he has a low BF%, it will be hard for him to lose any significant amount of weight without also losing a lot of muscle. If he has a BF% of 20, then he can surely go for it and probably gain some power out of it. However, his w/kg is probably equivalent to a cat 4 racer, he could gain a lot more from decent training before he could gain power by losing weight. He isn't at the point yet where he can only gain power by dropping weight.Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Because I'm a cyclist at his desired weight/height, so I know how it affects at least my own performance. I also want to point out that I am not one of those MFPers who thinks anyone under a BMI of 20 is anorexic, as many people here seem to think.
You make a good argument, thanks.
I'm no expert in caliper measurements either, but I think it would be fair to say that body composition and fat percentage can be determined much more clearly than the BMI scale.
Your points about population changes is an interesting one, of which you no doubt have more knowledge than me. However, to me at least, its a confusing message. I thought that BMI was a universally recognised scale? Surely the BF% (which BMI claims to calculate) is healthy or unhealthy for any person, regardless of activity? Surely the official BMI numbers and thresholds dont change depending on your activity levels? Maybe I'm wrong but it seems confusing.
For the last part, I totally agree. If he can lose BF then it can still be beneficial to his climbing. That doesn't mean its beneficial to his overall health and it doesnt mean it would be easy to do. And yes, his power needs a lot more work than his weight.
I agree that I think this is a point where BMI has been misapplied, it's not meant to estimate body fat percentage, per se. Statisticians hate point estimates because they are almost never accurate. What it is meant to do is estimate whether someone is under- or overfat based on their height and weight. Basically they take a distribution of people and make a range in which x% of people have a healthy body fat. The range changes depending on activity level because the body fat percentage for a certain height/weight will be different depending on activity level, as you have pointed out. So, someone with a BMI of 19 who is lightly active might have a BF% of 20, but someone with a BMI of 19 that is a professional athlete might have a BF% of 14. So if the underlying population changes, in this case to athletes, the BMI at which one will have too little body fat will probably be higher (because muscle is denser than fat, as we all know, thus a higher weight to height ratio for the same BF%). The intervals are then shifted upwards for athletes, downwards for excessively sedentary people.
Long story short: BMI is just a ratio they use that is correlated with BF% but doesn't necessarily estimate it. And in that case, if it is used to estimate BF% itself, it is incorrectly applied.
Also to add more examples of the change in underlying population: the BMI range for healthy according to the WHO is different for Asians, with the cutoff for obesity at 27 instead of 30, again because they tend to have a higher BF% for a certain BMI.1 -
deannalfisher wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
do you understand statistics at all and standard deviations? 25% of the population will fit into typically 1 standard deviation of the avg population - which is why they pick that range
68% will fit in one standard deviation, and 95% will fall within two.
3 -
mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
If by measurements you mean caliper measurements done by someone who knows what they are doing? Then probably, but measurements themselves aren't particularly accurate.
I also think you and I have a different definition of what it means to be accurate. Individual BMI isn't meant to be a point estimate of someone's body fat percentage, it's meant as an estimate to see what category they fall into and their risks of having an unhealthy body fat percentage based on that category. If people come to MFP with a BMI of 35, it's pretty likely they are indeed obese. As for how can something with such a wide range be accurate, you do realize what it is trying to estimate right? The range of healthy body fat percentages is also wide (14% to 31% for women and 6% to 22% for men), in order to include them all there would also likely be a wide weight range. You're really asking how can such a wide range of weight be healthy and that is not a question for BMI. (Aside from that, statistical accuracy doesn't care about what you think about interval widths, if such a wide interval is accurate for a sample, it's likely mathematically accurate for the population, whether you like how the math works or not).
18.5 is on the verge of underweight for anyone, for someone like him who regularly cycles, it's likely underweight, meaning he likely has a very low body fat percentage (especially since he is a man and likely has a lower body fat percentage than a woman at that weight). How will BMI affect his performance? It won't, but having a lower body fat percentage and trying to lose weight will, which is what BMI is estimating. If you are active and have a low BF%, you're just sacrificing muscle by losing weight, and at his height/weight, that's likely what he's doing. He's 5'9" and 66 kilos as a man, with an FTP of 220, he likely won't gain much by dieting. I say this as a 175cm (5'9") 56 kg (125lb) woman who has been this weight most of my adult life and is also an avid cyclist.
So would you consider caliper measurements done by someone who knows what they're doing to be less accurate than BMI or more?
I'm not sure what you mean in the first few sentences of the 2nd paragraph. Is BMI meant to determine body fat or not?
I agree with you about extreme BMI numbers being "likely" to correlate with obesity, but that can still be better understood by talking about the persons body composition rather than blindly applying a number and therefore a category to them.
I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
You said originally that his BMI will probably negatively affect his performance. Now you say it won't......
Why would having a lower body fat % negatively affect his performance if he lowers that percentage further? He's specifically interested in climbing hills, where a good power to weight ratio is essential. If that fat isn't assisting his power up the hills then it is hindering his power/weight ratio and slowing him down. I won't comment on whether thats a healthy choice, but I'm not sure how its possible to claim that it will negatively affect his performance.
Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Sorry, English isn't my native language so perhaps the language in my post was confusing. Yes, I think caliper measurements done by a "professional" are probably more accurate at assessing BF% than BMI (but I also don't know whether this is true, I have never looked up the study of accuracy of calipers).
BMI, itself, the number, does nothing more than put you into a category, it's the categories which are useful. I do not think BMI, itself, estimates BF% as a point estimate (by point estimate I mean it is not accurate to say a BMI of X equals X% bodyfat, point estimates are never accurate and no statistician would claim such), BMI can, however, make an estimate of whether one is over- or underfat.I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
I say likely because that is how statistics work. BMI is a statistical estimate. It does nothing more than give "likelihoods" and those likelihoods vary with different lifestyle factors (because the underlying population changes, if you want to know the mathematical reason). If we trust BMI then we can only say likelihood because that is all it tells us: likelihoods and risks.
18.5 is the cutoff point for a healthy BMI, taken from the whole population, with no other information, one could only say he was likely on the verge of underweight (because BMI is a likelihood estimation). If we know that he is an active cyclist, the underlying population changes. We are now not looking at BMI for the average population, we are looking at BMI for active cyclists. This distribution will look different. In this distribution, the cutoff BMI for being underfat will likely be higher.
As for BMI negatively affecting his performance, I must have worded it improperly or you misunderstood what I meant, I think having a low BF% and trying to lose weight will negatively affect his performance. I do not think BMI, itself, will negatively affect his performance, it is nothing more than an inferential statistic. If he has a low BF%, it will be hard for him to lose any significant amount of weight without also losing a lot of muscle. If he has a BF% of 20, then he can surely go for it and probably gain some power out of it. However, his w/kg is probably equivalent to a cat 4 racer, he could gain a lot more from decent training before he could gain power by losing weight. He isn't at the point yet where he can only gain power by dropping weight.Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Because I'm a cyclist at his desired weight/height, so I know how it affects at least my own performance. I also want to point out that I am not one of those MFPers who thinks anyone under a BMI of 20 is anorexic, as many people here seem to think.
You make a good argument, thanks.
I'm no expert in caliper measurements either, but I think it would be fair to say that body composition and fat percentage can be determined much more clearly than the BMI scale.
Your points about population changes is an interesting one, of which you no doubt have more knowledge than me. However, to me at least, its a confusing message. I thought that BMI was a universally recognised scale? Surely the BF% (which BMI claims to calculate) is healthy or unhealthy for any person, regardless of activity? Surely the official BMI numbers and thresholds dont change depending on your activity levels? Maybe I'm wrong but it seems confusing.
For the last part, I totally agree. If he can lose BF then it can still be beneficial to his climbing. That doesn't mean its beneficial to his overall health and it doesnt mean it would be easy to do. And yes, his power needs a lot more work than his weight.
I agree that I think this is a point where BMI has been misapplied, it's not meant to estimate body fat percentage, per se. Statisticians hate point estimates because they are almost never accurate. What it is meant to do is estimate whether someone is under- or overfat based on their height and weight. Basically they take a distribution of people and make a range in which x% of people have a healthy body fat. The range changes depending on activity level because the body fat percentage for a certain height/weight will be different depending on activity level, as you have pointed out. So, someone with a BMI of 19 who is lightly active might have a BF% of 20, but someone with a BMI of 19 that is a professional athlete might have a BF% of 14. So if the underlying population changes, in this case to athletes, the BMI at which one will have too little body fat will probably be higher (because muscle is denser than fat, as we all know, thus a higher weight to height ratio for the same BF%). The intervals are then shifted upwards for athletes, downwards for excessively sedentary people.
Long story short: BMI is just a ratio they use that is correlated with BF% but doesn't necessarily estimate it. And in that case, if it is used to estimate BF% itself, it is incorrectly applied.
That's very interesting, thanks. You'll have to bear with me, in the hope that I've properly understood what you said. If i have understood, then what I don't still understand is this movement of the scale that you refer to. I've not seen any bmi calculators that take in to account your level of activity. Indeed, its clear from other websites that a lot of people with lots of muscle would be classed as overweight on the BMI scale, hence making it a useless tool.
And lastly, I still dont really understand the distinction between being correlated to BF% and not estimating it. Is this not the same thing? The general consensus of BMI is to indicate whether you are at risk of health problems due to excess fat. Hence the classification of "obese". If BMI were to be followed by everyone then doctors would be telling weight lifters to lose weight because the muscle would causes coronary problems.
Bear with me, I'm trying to learn
1 -
mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »mattrus1989 wrote: »Is this a reference to this thread? https://community.myfitnesspal.com/en/discussion/10682410/need-help-and-advice-to-lose-more-weight-and-achieve-a-cyclist-climber-body
not exclusively although that thread does have elements of what I'm talking about, yes
I don't think that thread is the hill to die on. Regardless of the error rate involved with BMI, it's probably pretty accurate in predicting whether or not one is underweight if they are highly active. A BMI of 18.5 for a very active cyclist is likely underweight and will probably negatively affect performance (and I say that as a cyclist with a BMI of 18.5).
As for other mentions of BMI, it's not inaccurate enough that it should be disposed of completely, and for most people coming to this website, it's probably a good thing to keep an eye on. It also wouldn't hurt to choose goal weights for most people here based on BMI, especially if they don't have another way of accurately measuring their body fat.
I think we've already concluded that it wasn't one thread in isolation, so no ones dying on any hills.
How can something with such a broad range of acceptable measurements be classed as "pretty accurate"? Using myself as the example again, I wouldnt consider a 25% range of variability to be "pretty accurate".
I'm intrigued about the relationship between BMI and being active. Why is 18.5 (a supposedly healthy level of BMI) unhealthy for a cyclist and how would it negatively affect performance?
For weight loss, it seems to me that taking measurements of key areas of the body (as MFP allows you to do) would give you a better indication of body composition vs weight.
If by measurements you mean caliper measurements done by someone who knows what they are doing? Then probably, but measurements themselves aren't particularly accurate.
I also think you and I have a different definition of what it means to be accurate. Individual BMI isn't meant to be a point estimate of someone's body fat percentage, it's meant as an estimate to see what category they fall into and their risks of having an unhealthy body fat percentage based on that category. If people come to MFP with a BMI of 35, it's pretty likely they are indeed obese. As for how can something with such a wide range be accurate, you do realize what it is trying to estimate right? The range of healthy body fat percentages is also wide (14% to 31% for women and 6% to 22% for men), in order to include them all there would also likely be a wide weight range. You're really asking how can such a wide range of weight be healthy and that is not a question for BMI. (Aside from that, statistical accuracy doesn't care about what you think about interval widths, if such a wide interval is accurate for a sample, it's likely mathematically accurate for the population, whether you like how the math works or not).
18.5 is on the verge of underweight for anyone, for someone like him who regularly cycles, it's likely underweight, meaning he likely has a very low body fat percentage (especially since he is a man and likely has a lower body fat percentage than a woman at that weight). How will BMI affect his performance? It won't, but having a lower body fat percentage and trying to lose weight will, which is what BMI is estimating. If you are active and have a low BF%, you're just sacrificing muscle by losing weight, and at his height/weight, that's likely what he's doing. He's 5'9" and 66 kilos as a man, with an FTP of 220, he likely won't gain much by dieting. I say this as a 175cm (5'9") 56 kg (125lb) woman who has been this weight most of my adult life and is also an avid cyclist.
So would you consider caliper measurements done by someone who knows what they're doing to be less accurate than BMI or more?
I'm not sure what you mean in the first few sentences of the 2nd paragraph. Is BMI meant to determine body fat or not?
I agree with you about extreme BMI numbers being "likely" to correlate with obesity, but that can still be better understood by talking about the persons body composition rather than blindly applying a number and therefore a category to them.
I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
You said originally that his BMI will probably negatively affect his performance. Now you say it won't......
Why would having a lower body fat % negatively affect his performance if he lowers that percentage further? He's specifically interested in climbing hills, where a good power to weight ratio is essential. If that fat isn't assisting his power up the hills then it is hindering his power/weight ratio and slowing him down. I won't comment on whether thats a healthy choice, but I'm not sure how its possible to claim that it will negatively affect his performance.
Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Sorry, English isn't my native language so perhaps the language in my post was confusing. Yes, I think caliper measurements done by a "professional" are probably more accurate at assessing BF% than BMI (but I also don't know whether this is true, I have never looked up the study of accuracy of calipers).
BMI, itself, the number, does nothing more than put you into a category, it's the categories which are useful. I do not think BMI, itself, estimates BF% as a point estimate (by point estimate I mean it is not accurate to say a BMI of X equals X% bodyfat, point estimates are never accurate and no statistician would claim such), BMI can, however, make an estimate of whether one is over- or underfat.I still don't understand the link youre making with cycling and BMI. Why does him being someone "who regularly cycles" have anything to do with being "likely underweight"? If we trust BMI then hes either underweight or he isnt, regardless of whether he cycles or sits on the couch all day.
I say likely because that is how statistics work. BMI is a statistical estimate. It does nothing more than give "likelihoods" and those likelihoods vary with different lifestyle factors (because the underlying population changes, if you want to know the mathematical reason). If we trust BMI then we can only say likelihood because that is all it tells us: likelihoods and risks.
18.5 is the cutoff point for a healthy BMI, taken from the whole population, with no other information, one could only say he was likely on the verge of underweight (because BMI is a likelihood estimation). If we know that he is an active cyclist, the underlying population changes. We are now not looking at BMI for the average population, we are looking at BMI for active cyclists. This distribution will look different. In this distribution, the cutoff BMI for being underfat will likely be higher.
As for BMI negatively affecting his performance, I must have worded it improperly or you misunderstood what I meant, I think having a low BF% and trying to lose weight will negatively affect his performance. I do not think BMI, itself, will negatively affect his performance, it is nothing more than an inferential statistic. If he has a low BF%, it will be hard for him to lose any significant amount of weight without also losing a lot of muscle. If he has a BF% of 20, then he can surely go for it and probably gain some power out of it. However, his w/kg is probably equivalent to a cat 4 racer, he could gain a lot more from decent training before he could gain power by losing weight. He isn't at the point yet where he can only gain power by dropping weight.Lastly, I'm not sure why you're telling me your statistics. What difference does that make to this discussion?
Because I'm a cyclist at his desired weight/height, so I know how it affects at least my own performance. I also want to point out that I am not one of those MFPers who thinks anyone under a BMI of 20 is anorexic, as many people here seem to think.
You make a good argument, thanks.
I'm no expert in caliper measurements either, but I think it would be fair to say that body composition and fat percentage can be determined much more clearly than the BMI scale.
Your points about population changes is an interesting one, of which you no doubt have more knowledge than me. However, to me at least, its a confusing message. I thought that BMI was a universally recognised scale? Surely the BF% (which BMI claims to calculate) is healthy or unhealthy for any person, regardless of activity? Surely the official BMI numbers and thresholds dont change depending on your activity levels? Maybe I'm wrong but it seems confusing.
For the last part, I totally agree. If he can lose BF then it can still be beneficial to his climbing. That doesn't mean its beneficial to his overall health and it doesnt mean it would be easy to do. And yes, his power needs a lot more work than his weight.
I agree that I think this is a point where BMI has been misapplied, it's not meant to estimate body fat percentage, per se. Statisticians hate point estimates because they are almost never accurate. What it is meant to do is estimate whether someone is under- or overfat based on their height and weight. Basically they take a distribution of people and make a range in which x% of people have a healthy body fat. The range changes depending on activity level because the body fat percentage for a certain height/weight will be different depending on activity level, as you have pointed out. So, someone with a BMI of 19 who is lightly active might have a BF% of 20, but someone with a BMI of 19 that is a professional athlete might have a BF% of 14. So if the underlying population changes, in this case to athletes, the BMI at which one will have too little body fat will probably be higher (because muscle is denser than fat, as we all know, thus a higher weight to height ratio for the same BF%). The intervals are then shifted upwards for athletes, downwards for excessively sedentary people.
Long story short: BMI is just a ratio they use that is correlated with BF% but doesn't necessarily estimate it. And in that case, if it is used to estimate BF% itself, it is incorrectly applied.
That's very interesting, thanks. You'll have to bear with me, in the hope that I've properly understood what you said. If i have understood, then what I don't still understand is this movement of the scale that you refer to. I've not seen any bmi calculators that take in to account your level of activity. Indeed, its clear from other websites that a lot of people with lots of muscle would be classed as overweight on the BMI scale, hence making it a useless tool.
And lastly, I still dont really understand the distinction between being correlated to BF% and not estimating it. Is this not the same thing? The general consensus of BMI is to indicate whether you are at risk of health problems due to excess fat. Hence the classification of "obese". If BMI were to be followed by everyone then doctors would be telling weight lifters to lose weight because the muscle would causes coronary problems.
Bear with me, I'm trying to learn
Yes, it would be a much more accurate to take into account activity level (over time, obviously, since being extremely active for a week won't make you an athlete), but the underlying distribution these websites use is for the average population, since that is the original sample used to calculate BMI. If we could create different BMI intervals for different activity levels, it would be more accurate.
As for being correlated with BF%, correlation, at least here, just means they move in the same direction (mathematically for other functions it means the functions have some sort of relationship), so a higher BMI usually means a higher BF%. Correlation is not absolute though, it ranges from -1 (moving completely opposite) to 1 (moving perfectly together). BMI is somewhere between 0 and 1. They move in the same direction, but not perfectly, that means, on average, higher BMI will mean higher body fat percentage, but not always. Things like running vs calories burned are probably closer to a correlation of 1, the more you run, the more calories you burn, pretty much always, and we can calculate the extra calorie burn from x minutes of running pretty accurately. On the other hand, things like education and income are less than 1, but still more than zero (in general, people who have higher degrees earn more, but there are always some outliers and some overlap, some high school dropouts start million dollar companies, some people with PhDs work at fast food restaurants). Not sure if I'm overly simplifying it for you, but essentially BMI correlates with BF%, but not perfectly, there will be some outliers and some overlap. The more data you add that also correlates with BF%, like activity level, the more accurate it will be (because the "model" will now have a higher correlation).
Basically, BF% is influenced by a number of factors, weight and height are two of them, but not all of them, so adding more, makes it correlate more, makes it more accurate. Hence why it's only useful as an initial assessment in order to find cases that deserve more scrutiny and more data points.1 -
Thanks! I wish I could say that was oversimplifying it for me but I only just managed to follow. Very interesting!1
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Having read it a 2nd time.....and a 3rd, that all makes sense. Thanks for taking the time to explain it.
Given time to consider all this, it seems that we all agree in the most part, because applying this theory to a large population makes a lot of sense for wide and general application. I'll stand by my original belief though that applying that to an individual without consideration for the other factors is not going to be accurate, which I think most people agree with me on. I don't think I can agree on using it myself but I can see why others may want to0 -
I use the healthy weight range which is based on BMI a lot here, so I'll chime in. When a poster gives limited info and their goal weight seems really low or high, or the rate of loss they are aiming for is aggressive, I find it an easy way to explain the situation. Sure it would be great if the OP would answer a bunch of questions about stats, but very often they don't have those numbers or never post again in the thread. I'd rather give them generalized advice based on a statistical avg than nothing.
In threads about athletic performance and norms, I try to stay out of discussions about numbers because I'm not an athlete and the OP may very well already work with pros who know more than I do.
But the average newbie doesn't know their BF%, how to accurately measure themselves, or what a healthy weight even means, is very unlikely to be overly muscular or lean, and doesn't want to provide much personal info on a public forum. In those circumstances I think BMI is a useful generality to work with.14 -
I use the healthy weight range which is based on BMI a lot here, so I'll chime in. When a poster gives limited info and their goal weight seems really low or high, or the rate of loss they are aiming for is aggressive, I find it an easy way to explain the situation. Sure it would be great if the OP would answer a bunch of questions about stats, but very often they don't have those numbers or never post again in the thread. I'd rather give them generalized advice based on a statistical avg than nothing.
In threads about athletic performance and norms, I try to stay out of discussions about numbers because I'm not an athlete and the OP may very well already work with pros who know more than I do.
But the average newbie doesn't know their BF%, how to accurately measure themselves, or what a healthy weight even means, is very unlikely to be overly muscular or lean, and doesn't want to provide much personal info on a public forum. In those circumstances I think BMI is a useful generality to work with.
Agreed. As usual, context matters. When talking with people who are just starting to try to lose weight and/or improve their health and fitness, and are trying to establish some kind of reasonable weight goal, BMI is a useful metric (and I rarely see it touted as the one single measure to be used as a reference, as the PP claimed).
Since the PP is a cyclist, I'd liken it to advice given to beginning bicyclists looking for their first bike and tips on how to start riding. At that point, they don't need power meters, carbon fiber wheels or aero bars, don't need to know their FTP or lactate threshold, don't need interval training programs, etc. - they need advice on getting a bike that fits and how to ride it without killing themselves. Once they stick around long enough to get a reasonable foundation established and have a bit of seat time, maybe they'll start to develop more specific goals - and then it's time to start diving into the nuts and bolts of things.
All the other stuff about BMI has been well and thoroughly hashed out in the hundreds of BMI threads before, and is still ongoing in a thread in the Debate forum.9 -
Deleting my past comment...I don't want to contribute to eating disorder-y thinking (just read the cyclist post.)3
This discussion has been closed.
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