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Is every single body in the world intended to be within the so-called healthy BMI range?
Replies
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stanmann571 wrote: »stanmann571 wrote: »stanmann571 wrote: »lemurcat12 wrote: »Here's one good comparison of BF% and BMI (given that the purpose of BMI is to act as a proxy for BF%): https://bmcobes.biomedcentral.com/articles/10.1186/2052-9538-1-9
Key findings (note, this is for white people in Australia, there are likely race-based differences):
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
*BMI particularly underestimates adiposity in elderly men (aged 70 years and older), but also in young men (aged 20–29 years).
That's different from another such study I recall seeing in the past, where it was much more likely to mischaracterize women as not obese when they were than obese when they were not. There was more mischaracterization for the overweight category in that one (this one focused on obesity measures only).
17.3+19.9=37.2% incorrect for women
31.6+46.1=77.7% incorrect for men
I know it's confusing, because the BMI chart includes a "overweight category" and the BF chart does not.
jdlobb already went with a more thorough analysis of the data. So I'll focus on something simple.
17.3+19.9=37.2% incorrect for women
31.6+46.1=77.7% incorrect for men
What you did above? Is quite simply not how numbers work. Take women,
17.3% of women who were identified as obese were not obese.
19.9% of women listed as not obese but actually were.
You can't however add the two together and claim a 37.2% error rate. Just think about it, otherwise I could say:
While 17.3% of women who were classified as obese weren't that means 82.7% of women were identified as obese by bmi were in fact obese
and since 19.9% of women were classified as not obese while they were it means 80.1% of women identified as not obese and weren't obese.
82.7% + 80.1% = 168.2% accurate for women.
BMI is clearly not 162.8% accurate for anything. You can't make the claim 37.2% incorrect for women and 77.7% incorrect for men.
You're partly correct. The correct solution is to average the numbers...
Which puts it at 18% for women and 36% for men ... Which is still well above the 5-10% required as above for being useful.
No, you don't average them either. BMI has three categories normal, overweight, and obese. To calculate an actual error rate you'd need to know the number of people identified as underweight and weren't, people identified as normal and weren't, the number of people identified as overweight and weren't, and the number of people who were identified as obese and weren't.
We literally can't make a determination on the overall accuracy of BMI based on the below two lines.
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
Edit: forgot underweight
And BODYFAT only has 3 Underweight normal and obese. Normal is often subdivided into Athletic fit and acceptable.
But if someone is NOT OBESE per Bodyfat, then they are normal
HTH
HAND
And BODYFAT only has 3 Underweight normal and obese. Normal is often subdivided into Athletic fit and acceptable.
is literally contradicted by
But if someone is NOT OBESE per Bodyfat, then they are normal
two categories or three?
Since 3, still not averaged and still impossible to make an accurate determination of bmi accuracy based on
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%2 -
stanmann571 wrote: »stanmann571 wrote: »stanmann571 wrote: »lemurcat12 wrote: »Here's one good comparison of BF% and BMI (given that the purpose of BMI is to act as a proxy for BF%): https://bmcobes.biomedcentral.com/articles/10.1186/2052-9538-1-9
Key findings (note, this is for white people in Australia, there are likely race-based differences):
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
*BMI particularly underestimates adiposity in elderly men (aged 70 years and older), but also in young men (aged 20–29 years).
That's different from another such study I recall seeing in the past, where it was much more likely to mischaracterize women as not obese when they were than obese when they were not. There was more mischaracterization for the overweight category in that one (this one focused on obesity measures only).
17.3+19.9=37.2% incorrect for women
31.6+46.1=77.7% incorrect for men
I know it's confusing, because the BMI chart includes a "overweight category" and the BF chart does not.
jdlobb already went with a more thorough analysis of the data. So I'll focus on something simple.
17.3+19.9=37.2% incorrect for women
31.6+46.1=77.7% incorrect for men
What you did above? Is quite simply not how numbers work. Take women,
17.3% of women who were identified as obese were not obese.
19.9% of women listed as not obese but actually were.
You can't however add the two together and claim a 37.2% error rate. Just think about it, otherwise I could say:
While 17.3% of women who were classified as obese weren't that means 82.7% of women were identified as obese by bmi were in fact obese
and since 19.9% of women were classified as not obese while they were it means 80.1% of women identified as not obese and weren't obese.
82.7% + 80.1% = 168.2% accurate for women.
BMI is clearly not 162.8% accurate for anything. You can't make the claim 37.2% incorrect for women and 77.7% incorrect for men.
You're partly correct. The correct solution is to average the numbers...
Which puts it at 18% for women and 36% for men ... Which is still well above the 5-10% required as above for being useful.
No, you don't average them either. BMI has three categories normal, overweight, and obese. To calculate an actual error rate you'd need to know the number of people identified as underweight and weren't, people identified as normal and weren't, the number of people identified as overweight and weren't, and the number of people who were identified as obese and weren't.
We literally can't make a determination on the overall accuracy of BMI based on the below two lines.
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
Edit: forgot underweight
And BODYFAT only has 3 Underweight normal and obese. Normal is often subdivided into Athletic fit and acceptable.
But if someone is NOT OBESE per Bodyfat, then they are normal
HTH
HAND
NO. you did not read it. At all. Even the charts YOU posted from SOMEWHERE ELSE had an "ideal weight" category.
How are you possibly this obtuse? You must be trolling at this point.
i know you think there are only 3 because only 3 are shown in Table 4. But please, add the numbers. they do not add to 100. Because this entire study simply IGNORES anybody that has a healthy BMI or ideal BF%4 -
stanmann571 wrote: »Aaron_K123 wrote: »stanmann571 wrote: »It's great for populations. But wildly useless for individuals.
Yeah. And? Its for population analysis. If people want to misuse it and then other people want to complain about it because it got misused I don't know how much I care about that to be honest.
Except it's not people misusing it. it's insurance companies and employers and doctors.
I'm pretty sure they are using it on populations of people. You do realize populations are comprised of individuals right?
Anyways I am about two steps past taking this thread seriously and am probably on my way out. Its just rehashing the same two points over and over again at this point. I'm not mad, just bored.5 -
Aaron_K123 wrote: »stanmann571 wrote: »Aaron_K123 wrote: »stanmann571 wrote: »It's great for populations. But wildly useless for individuals.
Yeah. And? Its for population analysis. If people want to misuse it and then other people want to complain about it because it got misused I don't know how much I care about that to be honest.
Except it's not people misusing it. it's insurance companies and employers and doctors.
I'm pretty sure they are using it on populations of people. You do realize populations are comprised of individuals right?
insurance companies use it because it's reasonably predictive, and more consistent and cheaper to attain than BF%.
If BF% were as easy and cheep to obtain, they would ABSOLUTELY use it, because it's more predictive, and insurance is an actuarial game, accuracy is important. There's no conspiracy to charge body builders higher premiums, that's stupid.4 -
stanmann571 wrote: »stanmann571 wrote: »stanmann571 wrote: »lemurcat12 wrote: »Here's one good comparison of BF% and BMI (given that the purpose of BMI is to act as a proxy for BF%): https://bmcobes.biomedcentral.com/articles/10.1186/2052-9538-1-9
Key findings (note, this is for white people in Australia, there are likely race-based differences):
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
*BMI particularly underestimates adiposity in elderly men (aged 70 years and older), but also in young men (aged 20–29 years).
That's different from another such study I recall seeing in the past, where it was much more likely to mischaracterize women as not obese when they were than obese when they were not. There was more mischaracterization for the overweight category in that one (this one focused on obesity measures only).
17.3+19.9=37.2% incorrect for women
31.6+46.1=77.7% incorrect for men
I know it's confusing, because the BMI chart includes a "overweight category" and the BF chart does not.
jdlobb already went with a more thorough analysis of the data. So I'll focus on something simple.
17.3+19.9=37.2% incorrect for women
31.6+46.1=77.7% incorrect for men
What you did above? Is quite simply not how numbers work. Take women,
17.3% of women who were identified as obese were not obese.
19.9% of women listed as not obese but actually were.
You can't however add the two together and claim a 37.2% error rate. Just think about it, otherwise I could say:
While 17.3% of women who were classified as obese weren't that means 82.7% of women were identified as obese by bmi were in fact obese
and since 19.9% of women were classified as not obese while they were it means 80.1% of women identified as not obese and weren't obese.
82.7% + 80.1% = 168.2% accurate for women.
BMI is clearly not 162.8% accurate for anything. You can't make the claim 37.2% incorrect for women and 77.7% incorrect for men.
You're partly correct. The correct solution is to average the numbers...
Which puts it at 18% for women and 36% for men ... Which is still well above the 5-10% required as above for being useful.
No, you don't average them either. BMI has three categories normal, overweight, and obese. To calculate an actual error rate you'd need to know the number of people identified as underweight and weren't, people identified as normal and weren't, the number of people identified as overweight and weren't, and the number of people who were identified as obese and weren't.
We literally can't make a determination on the overall accuracy of BMI based on the below two lines.
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
Edit: forgot underweight
And BODYFAT only has 3 Underweight normal and obese. Normal is often subdivided into Athletic fit and acceptable.
But if someone is NOT OBESE per Bodyfat, then they are normal
HTH
HAND
NO. you did not read it. At all. Even the charts YOU posted from SOMEWHERE ELSE had an "ideal weight" category.
How are you possibly this obtuse? You must be trolling at this point.
i know you think there are only 3 because only 3 are shown in Table 4. But please, add the numbers. they do not add to 100. Because this entire study simply IGNORES anybody that has a healthy BMI or ideal BF%
Do you not understand that "acceptable" and "ideal" are still "normal"???
How are you possibly this obtuse? You must be trolling at this point.2 -
stanmann571 wrote: »stanmann571 wrote: »stanmann571 wrote: »stanmann571 wrote: »lemurcat12 wrote: »Here's one good comparison of BF% and BMI (given that the purpose of BMI is to act as a proxy for BF%): https://bmcobes.biomedcentral.com/articles/10.1186/2052-9538-1-9
Key findings (note, this is for white people in Australia, there are likely race-based differences):
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
*BMI particularly underestimates adiposity in elderly men (aged 70 years and older), but also in young men (aged 20–29 years).
That's different from another such study I recall seeing in the past, where it was much more likely to mischaracterize women as not obese when they were than obese when they were not. There was more mischaracterization for the overweight category in that one (this one focused on obesity measures only).
17.3+19.9=37.2% incorrect for women
31.6+46.1=77.7% incorrect for men
I know it's confusing, because the BMI chart includes a "overweight category" and the BF chart does not.
jdlobb already went with a more thorough analysis of the data. So I'll focus on something simple.
17.3+19.9=37.2% incorrect for women
31.6+46.1=77.7% incorrect for men
What you did above? Is quite simply not how numbers work. Take women,
17.3% of women who were identified as obese were not obese.
19.9% of women listed as not obese but actually were.
You can't however add the two together and claim a 37.2% error rate. Just think about it, otherwise I could say:
While 17.3% of women who were classified as obese weren't that means 82.7% of women were identified as obese by bmi were in fact obese
and since 19.9% of women were classified as not obese while they were it means 80.1% of women identified as not obese and weren't obese.
82.7% + 80.1% = 168.2% accurate for women.
BMI is clearly not 162.8% accurate for anything. You can't make the claim 37.2% incorrect for women and 77.7% incorrect for men.
You're partly correct. The correct solution is to average the numbers...
Which puts it at 18% for women and 36% for men ... Which is still well above the 5-10% required as above for being useful.
No, you don't average them either. BMI has three categories normal, overweight, and obese. To calculate an actual error rate you'd need to know the number of people identified as underweight and weren't, people identified as normal and weren't, the number of people identified as overweight and weren't, and the number of people who were identified as obese and weren't.
We literally can't make a determination on the overall accuracy of BMI based on the below two lines.
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
Edit: forgot underweight
And BODYFAT only has 3 Underweight normal and obese. Normal is often subdivided into Athletic fit and acceptable.
But if someone is NOT OBESE per Bodyfat, then they are normal
HTH
HAND
NO. you did not read it. At all. Even the charts YOU posted from SOMEWHERE ELSE had an "ideal weight" category.
How are you possibly this obtuse? You must be trolling at this point.
i know you think there are only 3 because only 3 are shown in Table 4. But please, add the numbers. they do not add to 100. Because this entire study simply IGNORES anybody that has a healthy BMI or ideal BF%
Do you not understand that "acceptable" and "ideal" are still "normal"???
How are you possibly this obtuse? You must be trolling at this point.
this has to be a joke.
The study breaks BF% into 4 categories. Underweight, Ideal Weight, Overweight, and Obese.
These 4 categories mirror the 4 categories of BMI.
Table 1 makes this plainly clear.
this quote
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
CLEARLY only concerns whether people are in the UPPER MOST category, obese, in either or both categories.
It is not, in any way, whatso ever, saying that 17.3% of women and 31.6% of men identified as obese are NORMAL weight.
It is saying that they were OVERWEIGHT. Which still means they were above 20.6% BF to 24.2% BF depending on age for men, and 36% to 37.2% for women.3 -
stanmann571 wrote: »stanmann571 wrote: »stanmann571 wrote: »stanmann571 wrote: »lemurcat12 wrote: »Here's one good comparison of BF% and BMI (given that the purpose of BMI is to act as a proxy for BF%): https://bmcobes.biomedcentral.com/articles/10.1186/2052-9538-1-9
Key findings (note, this is for white people in Australia, there are likely race-based differences):
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
*BMI particularly underestimates adiposity in elderly men (aged 70 years and older), but also in young men (aged 20–29 years).
That's different from another such study I recall seeing in the past, where it was much more likely to mischaracterize women as not obese when they were than obese when they were not. There was more mischaracterization for the overweight category in that one (this one focused on obesity measures only).
17.3+19.9=37.2% incorrect for women
31.6+46.1=77.7% incorrect for men
I know it's confusing, because the BMI chart includes a "overweight category" and the BF chart does not.
jdlobb already went with a more thorough analysis of the data. So I'll focus on something simple.
17.3+19.9=37.2% incorrect for women
31.6+46.1=77.7% incorrect for men
What you did above? Is quite simply not how numbers work. Take women,
17.3% of women who were identified as obese were not obese.
19.9% of women listed as not obese but actually were.
You can't however add the two together and claim a 37.2% error rate. Just think about it, otherwise I could say:
While 17.3% of women who were classified as obese weren't that means 82.7% of women were identified as obese by bmi were in fact obese
and since 19.9% of women were classified as not obese while they were it means 80.1% of women identified as not obese and weren't obese.
82.7% + 80.1% = 168.2% accurate for women.
BMI is clearly not 162.8% accurate for anything. You can't make the claim 37.2% incorrect for women and 77.7% incorrect for men.
You're partly correct. The correct solution is to average the numbers...
Which puts it at 18% for women and 36% for men ... Which is still well above the 5-10% required as above for being useful.
No, you don't average them either. BMI has three categories normal, overweight, and obese. To calculate an actual error rate you'd need to know the number of people identified as underweight and weren't, people identified as normal and weren't, the number of people identified as overweight and weren't, and the number of people who were identified as obese and weren't.
We literally can't make a determination on the overall accuracy of BMI based on the below two lines.
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
Edit: forgot underweight
And BODYFAT only has 3 Underweight normal and obese. Normal is often subdivided into Athletic fit and acceptable.
But if someone is NOT OBESE per Bodyfat, then they are normal
HTH
HAND
NO. you did not read it. At all. Even the charts YOU posted from SOMEWHERE ELSE had an "ideal weight" category.
How are you possibly this obtuse? You must be trolling at this point.
i know you think there are only 3 because only 3 are shown in Table 4. But please, add the numbers. they do not add to 100. Because this entire study simply IGNORES anybody that has a healthy BMI or ideal BF%
Do you not understand that "acceptable" and "ideal" are still "normal"???
How are you possibly this obtuse? You must be trolling at this point.
this has to be a joke.
The study breaks BF% into 4 categories. Underweight, Ideal Weight, Overweight, and Obese.
These 4 categories mirror the 4 categories of BMI.
Table 1 makes this plainly clear.
this quote
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
CLEARLY only concerns whether people are in the UPPER MOST category, obese, in either or both categories.
It is not, in any way, whatso ever, saying that 17.3% of women and 31.6% of men identified as obese are NORMAL weight.
It is saying that they were OVERWEIGHT. Which still means they were above 20.6% BF to 24.2% BF depending on age for men, and 36% to 37.2% for women .
WHICH IS DEFINED by BF standards as NORMAL.
You're getting hung up and confused.
It doesn't matter how you subdivide normal.
https://www.acefitness.org/education-and-resources/lifestyle/blog/112/what-are-the-guidelines-for-percentage-of-body-fat-loss3 -
NorthCascades wrote: »Aaron_K123 wrote: »Aaron_K123 wrote: »stanmann571 wrote: »Aaron_K123 wrote: »Aaron_K123 wrote: »Viking_Batman wrote: »If the world went by BMI
Arnold Schwarzenegger in his prime would be considered super morbidly obese as would Dwayne 'the rock' Johnson, it's a dated measurement of health.
That...is not...what BMI...is for. If you use a hammer to try to cut down a tree yeah you might think the hammer is a useless tool but maybe, just maybe, you just aren't using the hammer for its intended purpose. Maybe there is nothing wrong with a hammer as a tool.
BMI isn't for individuals, it is for populations. It is a statistical measure. If you attempt to use a tool for the wrong thing of course it doesn't work very well.
ok, let's be a little clear on something.
As a tool it predicts that 95% of people in a population would be approximately within the normal BMI range under normal conditions, with no extenuating factors. Not that any particular percentage of people WILL be in that range.
Likewise, on an individual level, it predicts that there is a 95% probability that any particular individual in a population would be in the normal BMI range baring external conditions or other factors.
Your average person would have a normal BMI if they didn't lead a sedentary lifestyle and each more calories than their body needs.
Likewise, your average person would have a normal BMI if they didn't spend hours a day in the gym cultivating extra-ordinary muscle mass.
If you, as an individual, do not have a "normal" BMI, then the next step is to take additional factors into consideration. If they are negative, not enough exercise and too much food, then they should be eliminated for the good of your health. If they are positive, lots of exercise and proper nutrition, then they should be encouraged. If they are outside of your control, disease or disorder, then they should be treated. But BMI provides a reasonable baseline estimate from which to start, and to identify if there are mitigating factors that need to be addressed (for good or bad.)
I was taking into account the idea of applying BMI as a metric of health (yes I understand that is not exactly what it is for but that is how people are using it). What I was saying was that for a given population 95% of the time if you apply BMI as a means to determine if someone is obese or not the answer you get will be right (BMI is 28, person is predicted to be obese...person is obese) while 5% it will be wrong (BMI is 28, person is predicted to be obese...person is not obese). One could argue that that is just a misapplication of BMI in the first place but I'm trying to speak to the context of its use within this debate.
So as a "rule for determining whether a person is obese" maybe it has a 95% accuracy (I made up that number, just giving it as an example). Maybe a DEXA scan has a 99.9% accuracy. If you are dealing with an individual and have both options then yeah go with the DEXA. If you are dealing with a large population and want to know what percentage is obese you aren't going to DEXA scan the entire populace so go with BMI.
BMI is not a normalized distribution. What is considered a "normal BMI" is not the peak of a bell curve or something it is based on studies of BMI compared to measures of body compisition. You could have a population where the majority of people do not have a "normal" BMI.
Except the actual accuracy isn't even close to 95%... it's closer to 70%
The accuracy would actually depend on the population. Presumably its more accurate in the population for which the model was initially created. I don't know what the accuracy is but I'm pretty sure it is above 50% anywhere and it probably varies population to population...I doubt it is one fixed value.
he's insistent that because one study found inconsistency between what BMI said was "obese" and what their cutoffs for BF% said was "obese", that BMI is thus junk. He didn't really read the study, he just pulled out a choice quote that somebody else found and posted and ran with it.
As I repeatedly pointed out, the australian study actually makes the case that BMI is overly broad, and more people are obese than BMI says. Which is literally the exact opposite of why most people in this thread hate BMI.
Did you try kicking him in the dick?
New thread in the support forum: "kick him in the dick button is missing."
I'd maybe be willing to bet that's already in chit-chat.
2 -
10 -
Generally speaking, it’s a good range for most people; unless you’re an athletes, got a health condition, or training.
But I really don’t care if other people are within the BMI or not. I’ve never asked or wondered. A person’s body weight, fat percentage, health, fitness are their own business.
But I do have my own stantdards of what’s attractive and what’s not. I’m not gonna force it on others and theirs isn’t gonna change mine.2 -
stanmann571 wrote: »stanmann571 wrote: »stanmann571 wrote: »stanmann571 wrote: »stanmann571 wrote: »lemurcat12 wrote: »Here's one good comparison of BF% and BMI (given that the purpose of BMI is to act as a proxy for BF%): https://bmcobes.biomedcentral.com/articles/10.1186/2052-9538-1-9
Key findings (note, this is for white people in Australia, there are likely race-based differences):
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
*BMI particularly underestimates adiposity in elderly men (aged 70 years and older), but also in young men (aged 20–29 years).
That's different from another such study I recall seeing in the past, where it was much more likely to mischaracterize women as not obese when they were than obese when they were not. There was more mischaracterization for the overweight category in that one (this one focused on obesity measures only).
17.3+19.9=37.2% incorrect for women
31.6+46.1=77.7% incorrect for men
I know it's confusing, because the BMI chart includes a "overweight category" and the BF chart does not.
jdlobb already went with a more thorough analysis of the data. So I'll focus on something simple.
17.3+19.9=37.2% incorrect for women
31.6+46.1=77.7% incorrect for men
What you did above? Is quite simply not how numbers work. Take women,
17.3% of women who were identified as obese were not obese.
19.9% of women listed as not obese but actually were.
You can't however add the two together and claim a 37.2% error rate. Just think about it, otherwise I could say:
While 17.3% of women who were classified as obese weren't that means 82.7% of women were identified as obese by bmi were in fact obese
and since 19.9% of women were classified as not obese while they were it means 80.1% of women identified as not obese and weren't obese.
82.7% + 80.1% = 168.2% accurate for women.
BMI is clearly not 162.8% accurate for anything. You can't make the claim 37.2% incorrect for women and 77.7% incorrect for men.
You're partly correct. The correct solution is to average the numbers...
Which puts it at 18% for women and 36% for men ... Which is still well above the 5-10% required as above for being useful.
No, you don't average them either. BMI has three categories normal, overweight, and obese. To calculate an actual error rate you'd need to know the number of people identified as underweight and weren't, people identified as normal and weren't, the number of people identified as overweight and weren't, and the number of people who were identified as obese and weren't.
We literally can't make a determination on the overall accuracy of BMI based on the below two lines.
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
Edit: forgot underweight
And BODYFAT only has 3 Underweight normal and obese. Normal is often subdivided into Athletic fit and acceptable.
But if someone is NOT OBESE per Bodyfat, then they are normal
HTH
HAND
NO. you did not read it. At all. Even the charts YOU posted from SOMEWHERE ELSE had an "ideal weight" category.
How are you possibly this obtuse? You must be trolling at this point.
i know you think there are only 3 because only 3 are shown in Table 4. But please, add the numbers. they do not add to 100. Because this entire study simply IGNORES anybody that has a healthy BMI or ideal BF%
Do you not understand that "acceptable" and "ideal" are still "normal"???
How are you possibly this obtuse? You must be trolling at this point.
this has to be a joke.
The study breaks BF% into 4 categories. Underweight, Ideal Weight, Overweight, and Obese.
These 4 categories mirror the 4 categories of BMI.
Table 1 makes this plainly clear.
this quote
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
CLEARLY only concerns whether people are in the UPPER MOST category, obese, in either or both categories.
It is not, in any way, whatso ever, saying that 17.3% of women and 31.6% of men identified as obese are NORMAL weight.
It is saying that they were OVERWEIGHT. Which still means they were above 20.6% BF to 24.2% BF depending on age for men, and 36% to 37.2% for women .
WHICH IS DEFINED by BF standards as NORMAL.
You're getting hung up and confused.
It doesn't matter how you subdivide normal.
https://www.acefitness.org/education-and-resources/lifestyle/blog/112/what-are-the-guidelines-for-percentage-of-body-fat-loss
the authors of the study divided BF% into 4 categories to correspond directly with BMI.
What you are saying is that somebody with a BMI of either "healthy weight" or "overweight" is normal.
They do not, not for one second, not in any way what so ever, say that somebody with an "ideal weight" or "overweight" BF% would be expected to fit into a "healthy weight" BMI.
Underweight = Underweight
Ideal Weight = Healthy Weight
Overweight = Overweight
Obese = Obese
Any % differences they present are PURELY drawn across those lines.
So they found that 17.3% of women and 31.6% of men identified as obese by BMI were overweight based on BF%, and that 19.9% of women and 41.6% of men identified as overweight by BMI were obese by BF%
Net/Net, this still means that BMI is too forgiving, and that it actually gives weight targets that are TOO HIGH for most people. WHICH I'M PRETTY SURE A LOT OF PEOPLE HERE WOULD HAVE A PROBLEM WITH.
2 -
Aaron_K123 wrote: »Aaron_K123 wrote: »stanmann571 wrote: »Aaron_K123 wrote: »Aaron_K123 wrote: »Viking_Batman wrote: »If the world went by BMI
Arnold Schwarzenegger in his prime would be considered super morbidly obese as would Dwayne 'the rock' Johnson, it's a dated measurement of health.
That...is not...what BMI...is for. If you use a hammer to try to cut down a tree yeah you might think the hammer is a useless tool but maybe, just maybe, you just aren't using the hammer for its intended purpose. Maybe there is nothing wrong with a hammer as a tool.
BMI isn't for individuals, it is for populations. It is a statistical measure. If you attempt to use a tool for the wrong thing of course it doesn't work very well.
ok, let's be a little clear on something.
As a tool it predicts that 95% of people in a population would be approximately within the normal BMI range under normal conditions, with no extenuating factors. Not that any particular percentage of people WILL be in that range.
Likewise, on an individual level, it predicts that there is a 95% probability that any particular individual in a population would be in the normal BMI range baring external conditions or other factors.
Your average person would have a normal BMI if they didn't lead a sedentary lifestyle and each more calories than their body needs.
Likewise, your average person would have a normal BMI if they didn't spend hours a day in the gym cultivating extra-ordinary muscle mass.
If you, as an individual, do not have a "normal" BMI, then the next step is to take additional factors into consideration. If they are negative, not enough exercise and too much food, then they should be eliminated for the good of your health. If they are positive, lots of exercise and proper nutrition, then they should be encouraged. If they are outside of your control, disease or disorder, then they should be treated. But BMI provides a reasonable baseline estimate from which to start, and to identify if there are mitigating factors that need to be addressed (for good or bad.)
I was taking into account the idea of applying BMI as a metric of health (yes I understand that is not exactly what it is for but that is how people are using it). What I was saying was that for a given population 95% of the time if you apply BMI as a means to determine if someone is obese or not the answer you get will be right (BMI is 28, person is predicted to be obese...person is obese) while 5% it will be wrong (BMI is 28, person is predicted to be obese...person is not obese). One could argue that that is just a misapplication of BMI in the first place but I'm trying to speak to the context of its use within this debate.
So as a "rule for determining whether a person is obese" maybe it has a 95% accuracy (I made up that number, just giving it as an example). Maybe a DEXA scan has a 99.9% accuracy. If you are dealing with an individual and have both options then yeah go with the DEXA. If you are dealing with a large population and want to know what percentage is obese you aren't going to DEXA scan the entire populace so go with BMI.
BMI is not a normalized distribution. What is considered a "normal BMI" is not the peak of a bell curve or something it is based on studies of BMI compared to measures of body compisition. You could have a population where the majority of people do not have a "normal" BMI.
Except the actual accuracy isn't even close to 95%... it's closer to 70%
The accuracy would actually depend on the population. Presumably its more accurate in the population for which the model was initially created. I don't know what the accuracy is but I'm pretty sure it is above 50% anywhere and it probably varies population to population...I doubt it is one fixed value.
he's insistent that because one study found inconsistency between what BMI said was "obese" and what their cutoffs for BF% said was "obese", that BMI is thus junk. He didn't really read the study, he just pulled out a choice quote that somebody else found and posted and ran with it.
As I repeatedly pointed out, the australian study actually makes the case that BMI is overly broad, and more people are obese than BMI says. Which is literally the exact opposite of why most people in this thread hate BMI.
Did you try kicking him in the dick?
http://www.bbc.com/news/420326291 -
Aaron_K123 wrote: »Viking_Batman wrote: »If the world went by BMI
Arnold Schwarzenegger in his prime would be considered super morbidly obese as would Dwayne 'the rock' Johnson, it's a dated measurement of health.
That...is not...what BMI...is for. If you use a hammer to try to cut down a tree yeah you might think the hammer is a useless tool but maybe, just maybe, you just aren't using the hammer for its intended purpose. Maybe there is nothing wrong with a hammer as a tool.
BMI isn't for individuals, it is for populations. It is a statistical measure. If you attempt to use a tool for the wrong thing of course it doesn't work very well.
ok, let's be a little clear on something.
As a tool it predicts that 95% of people in a population would be approximately within the normal BMI range under normal conditions, with no extenuating factors. Not that any particular percentage of people WILL be in that range.
Likewise, on an individual level, it predicts that there is a 95% probability that any particular individual in a population would be in the normal BMI range baring external conditions or other factors.
Your average person would have a normal BMI if they didn't lead a sedentary lifestyle and each more calories than their body needs.
Likewise, your average person would have a normal BMI if they didn't spend hours a day in the gym cultivating extra-ordinary muscle mass.
If you, as an individual, do not have a "normal" BMI, then the next step is to take additional factors into consideration. If they are negative, not enough exercise and too much food, then they should be eliminated for the good of your health. If they are positive, lots of exercise and proper nutrition, then they should be encouraged. If they are outside of your control, disease or disorder, then they should be treated. But BMI provides a reasonable baseline estimate from which to start, and to identify if there are mitigating factors that need to be addressed (for good or bad.)stanmann571 wrote: »stanmann571 wrote: »stanmann571 wrote: »stanmann571 wrote: »stanmann571 wrote: »lemurcat12 wrote: »Here's one good comparison of BF% and BMI (given that the purpose of BMI is to act as a proxy for BF%): https://bmcobes.biomedcentral.com/articles/10.1186/2052-9538-1-9
Key findings (note, this is for white people in Australia, there are likely race-based differences):
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
*BMI particularly underestimates adiposity in elderly men (aged 70 years and older), but also in young men (aged 20–29 years).
That's different from another such study I recall seeing in the past, where it was much more likely to mischaracterize women as not obese when they were than obese when they were not. There was more mischaracterization for the overweight category in that one (this one focused on obesity measures only).
17.3+19.9=37.2% incorrect for women
31.6+46.1=77.7% incorrect for men
I know it's confusing, because the BMI chart includes a "overweight category" and the BF chart does not.
jdlobb already went with a more thorough analysis of the data. So I'll focus on something simple.
17.3+19.9=37.2% incorrect for women
31.6+46.1=77.7% incorrect for men
What you did above? Is quite simply not how numbers work. Take women,
17.3% of women who were identified as obese were not obese.
19.9% of women listed as not obese but actually were.
You can't however add the two together and claim a 37.2% error rate. Just think about it, otherwise I could say:
While 17.3% of women who were classified as obese weren't that means 82.7% of women were identified as obese by bmi were in fact obese
and since 19.9% of women were classified as not obese while they were it means 80.1% of women identified as not obese and weren't obese.
82.7% + 80.1% = 168.2% accurate for women.
BMI is clearly not 162.8% accurate for anything. You can't make the claim 37.2% incorrect for women and 77.7% incorrect for men.
You're partly correct. The correct solution is to average the numbers...
Which puts it at 18% for women and 36% for men ... Which is still well above the 5-10% required as above for being useful.
No, you don't average them either. BMI has three categories normal, overweight, and obese. To calculate an actual error rate you'd need to know the number of people identified as underweight and weren't, people identified as normal and weren't, the number of people identified as overweight and weren't, and the number of people who were identified as obese and weren't.
We literally can't make a determination on the overall accuracy of BMI based on the below two lines.
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
Edit: forgot underweight
And BODYFAT only has 3 Underweight normal and obese. Normal is often subdivided into Athletic fit and acceptable.
But if someone is NOT OBESE per Bodyfat, then they are normal
HTH
HAND
NO. you did not read it. At all. Even the charts YOU posted from SOMEWHERE ELSE had an "ideal weight" category.
How are you possibly this obtuse? You must be trolling at this point.
i know you think there are only 3 because only 3 are shown in Table 4. But please, add the numbers. they do not add to 100. Because this entire study simply IGNORES anybody that has a healthy BMI or ideal BF%
Do you not understand that "acceptable" and "ideal" are still "normal"???
How are you possibly this obtuse? You must be trolling at this point.
this has to be a joke.
The study breaks BF% into 4 categories. Underweight, Ideal Weight, Overweight, and Obese.
These 4 categories mirror the 4 categories of BMI.
Table 1 makes this plainly clear.
this quote
*17.3% of women and 31.6% of men identified as obese according to BMI were not, based on BF%.
*19.9% of women and 46.1% of men who were NOT obese by BMI actually were by BF%
CLEARLY only concerns whether people are in the UPPER MOST category, obese, in either or both categories.
It is not, in any way, whatso ever, saying that 17.3% of women and 31.6% of men identified as obese are NORMAL weight.
It is saying that they were OVERWEIGHT. Which still means they were above 20.6% BF to 24.2% BF depending on age for men, and 36% to 37.2% for women .
WHICH IS DEFINED by BF standards as NORMAL.
You're getting hung up and confused.
It doesn't matter how you subdivide normal.
https://www.acefitness.org/education-and-resources/lifestyle/blog/112/what-are-the-guidelines-for-percentage-of-body-fat-loss
the authors of the study divided BF% into 4 categories to correspond directly with BMI.
What you are saying is that somebody with a BMI of either "healthy weight" or "overweight" is normal.
They do not, not for one second, not in any way what so ever, say that somebody with an "ideal weight" or "overweight" BF% would be expected to fit into a "healthy weight" BMI.
Underweight = Underweight
Ideal Weight = Healthy Weight
Overweight = Overweight
Obese = Obese
Any % differences they present are PURELY drawn across those lines.
So they found that 17.3% of women and 31.6% of men identified as obese by BMI were overweight based on BF%, and that 19.9% of women and 41.6% of men identified as overweight by BMI were obese by BF%
Net/Net, this still means that BMI is too forgiving, and that it actually gives weight targets that are TOO HIGH for most people. WHICH I'M PRETTY SURE A LOT OF PEOPLE HERE WOULD HAVE A PROBLEM WITH.
So it's NOT as you asserted a tool that makes a meaningful assertion for 95% of the population.
Ultimately, that's what it boils down to and all I was asserting
For 20% of women and 35% of men it gets it wrong
Half of those women and men are given false comfort and half false concern, but regardless, they're getting the wrong message.
Which is notwithstanding the part that Overweight BMI is misleadingly labeled.2 -
1
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Which is literally the exact opposite of why most people in this thread hate BMI.
I seriously doubt that "most people" in this thread "hate BMI."
Maybe one or two drop ins, probably no regular posters, but I suppose I could be wrong. Maybe those who "hate BMI" could identify themselves.2 -
accidentalpancake wrote: »This is me at 6lbs OVER the very tip top of my "healthy" BMI range:
Being overly muscular is not a prerequisite for there being variations in the applicability of BMI. At the outer edges of height distribution, there are similar, documented issues to those that are constantly pointed out for athletes and bodybuilders.
This is exactly why I said it doesn't really work for men as well as women. I think BMI is far more accurate for women. It makes absolutely NO sense we use the same scale for men and women given 110lbs on a male 5'4 is going to look vastly different from 5'4 female at the same weight.1 -
I just discovered that the CDC has a pretty good page addressing the question of BMI to BF% correlations, with citationsHow good is BMI as an indicator of body fatness?
The correlation between the BMI and body fatness is fairly strong1,2,3,7, but even if 2 people have the same BMI, their level of body fatness may differ12.
In general,
At the same BMI, women tend to have more body fat than men.
At the same BMI, Blacks have less body fat than do Whites13,14, and Asians have more body fat than do Whites15
At the same BMI, older people, on average, tend to have more body fat than younger adults.
At the same BMI, athletes have less body fat than do non-athletes.
The accuracy of BMI as an indicator of body fatness also appears to be higher in persons with higher levels of BMI and body fatness16. While, a person with a very high BMI (e.g., 35 kg/m2) is very likely to have high body fat, a relatively high BMI can be the results of either high body fat or high lean body mass (muscle and bone). A trained healthcare provider should perform appropriate health assessments in order to evaluate an individual’s health status and risks.
If an athlete or other person with a lot of muscle has a BMI over 25, is that person still considered to be overweight?
According to the BMI weight status categories, anyone with a BMI between 25 and 29.9 would be classified as overweight and anyone with a BMI over 30 would be classified as obese.
However, athletes may have a high BMI because of increased muscularity rather than increased body fatness. In general, a person who has a high BMI is likely to have body fatness and would be considered to be overweight or obese, but this may not apply to athletes. A trained healthcare provider should perform appropriate health assessments in order to evaluate an individual’s health status and risks.
References
1Garrow, J.S. & Webster, J., 1985. Quetelet’s index (W/H2) as a measure of fatness. Int. J. Obes., 9(2), pp.147–153.
2Freedman, D.S., Horlick, M. & Berenson, G.S., 2013. A comparison of the Slaughter skinfold-thickness equations and BMI in predicting body fatness and cardiovascular disease risk factor levels in children. Am. J. Clin. Nutr., 98(6), pp.1417–24.
3Wohlfahrt-Veje, C. et al., 2014. Body fat throughout childhood in 2647 healthy Danish children: agreement of BMI, waist circumference, skinfolds with dual X-ray absorptiometry. Eur. J. Clin. Nutr., 68(6), pp.664–70.
4Steinberger, J. et al., 2005. Comparison of body fatness measurements by BMI and skinfolds vs dual energy X-ray absorptiometry and their relation to cardiovascular risk factors in adolescents. Int. J. Obes., 29(11), pp.1346–1352.
5Sun, Q. et al., 2010. Comparison of dual-energy x-ray absorptiometric and anthropometric measures of adiposity in relation to adiposity-related biologic factors. Am. J. Epidemiol., 172(12), pp.1442–1454.
6Lawlor, D.A. et al., 2010. Association between general and central adiposity in childhood, and change in these, with cardiovascular risk factors in adolescence: prospective cohort study. BMJ, 341, p.c6224.
7Flegal, K.M. & Graubard, B.I., 2009. Estimates of excess deaths associated with body mass index and other anthropometric variables. Am. J. Clin. Nutr., 89(4), pp.1213–1219.
8Freedman, D.S. et al., 2009. Relation of body mass index and skinfold thicknesses to cardiovascular disease risk factors in children: the Bogalusa Heart Study. Am. J. Clin. Nutr., 90(1), pp.210–216.
9Willett, K. et al., 2006. Comparison of bioelectrical impedance and BMI in predicting obesity-related medical conditions. Obes. (Silver Spring), 14(3), pp.480–490.
10NHLBI. 2013. Managing Overweight and Obesity in Adults: Systematic Evidence Review from the Obesity Expert Panel[PDF – 5.98MB]
11Kuczmarski, R.J. et al., 2002. 2000 CDC Growth Charts for the United States: methods and development. Vital Health Stat. 11., 11(246), pp.1–190.
12Prentice, A.M. & Jebb, S.A., 2001. Beyond body mass index. Obes. Rev., 2(3), pp.141–7.
13Wagner, D.R. & Heyward, V.H., 2000. Measures of body composition in blacks and whites: a comparative review. Am. J. Clin. Nutr., 71(6), pp.1392–1402.
14Flegal, K.M. et al., 2010. High adiposity and high body mass index-for-age in US children and adolescents overall and by race-ethnic group. Am. J. Clin. Nutr., 91(4), pp.1020–6.
15Barba, C. et al., 2004. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet, 363(9403), pp.157–163.
16Bray, G.A. et al., 2001. Evaluation of body fat in fatter and leaner 10-y-old African American and white children: the Baton Rouge Children’s Study. Am. J. Clin. Nutr., 73(4), pp.687–702.
17Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults[PDF – 1.25MB].
18Bhaskaran K, Douglas I, Forbes H, dos-Santos-Silva I, Leon DA, Smeeth L. Body-mass index and risk of 22 specific cancers: a population-based cohort study of 5•24 million UK adults. Lancet. 2014 Aug 30;384(9945):755-65. doi: 10.1016/S0140-6736(14)60892-8. Epub 2014 Aug 13.
19Engstrom G, Hedblad B, Stavenow L, Lind P, Janzon L and Lingarde F. Inflammation- sensitive plasma proteins are associated with future weight gain. Diabetes. Aug 2003; 52(08): 2097-101.
20Marseglia L, Manti S, D’Angelo G, Nicotera A, Parisi E, DiRosa G, Gitto E, Arrigo T. Oxidative stress in obesity: a critical component in human diseases. International Journal of Molecular Sciences. Dec 2014; 16(1):378-400.
21Kasen, Stephanie, et al. “Obesity and psychopathology in women: a three decade prospective study.” International Journal of Obesity 32.3 (2008): 558-566.
22Luppino, Floriana S., et al. “Overweight, obesity, and depression: a systematic review and meta-analysis of longitudinal studies.” Archives of general psychiatry 67.3 (2010): 220-229.
23Han, T. S., et al. “Quality of life in relation to overweight and body fat distribution.” American Journal of Public Health 88.12 (1998): 1814-1820.5 -
Noreenmarie1234 wrote: »accidentalpancake wrote: »This is me at 6lbs OVER the very tip top of my "healthy" BMI range:
Being overly muscular is not a prerequisite for there being variations in the applicability of BMI. At the outer edges of height distribution, there are similar, documented issues to those that are constantly pointed out for athletes and bodybuilders.
This is exactly why I said it doesn't really work for men as well as women. I think BMI is far more accurate for women. It makes absolutely NO sense we use the same scale for men and women given 110lbs on a male 5'4 is going to look vastly different from 5'4 female at the same weight.
but that is why there is a range...
a man who is 5 ft 4 woudl be considered in a healthy weight range between 110 - 144...and that's why it can be applied to both genders.
3 -
lemurcat12 wrote: »Which is literally the exact opposite of why most people in this thread hate BMI.
I seriously doubt that "most people" in this thread "hate BMI."
Maybe one or two drop ins, probably no regular posters, but I suppose I could be wrong. Maybe those who "hate BMI" could identify themselves.
I was rather ambivalent toward BMI prior to this thread, but the longer it goes on, the more negative I am becoming. Oh wait, it's just the thread about BMI that I hate, not the measurement itself...9 -
@lemurcat12lemurcat12 wrote: »Which is literally the exact opposite of why most people in this thread hate BMI.
I seriously doubt that "most people" in this thread "hate BMI."
Maybe one or two drop ins, probably no regular posters, but I suppose I could be wrong. Maybe those who "hate BMI" could identify themselves.
I hate it because at a BMI of 24.8 I'm not an outlier and I would really like to be special.
6
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