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Is BMI an accurate way to know how much I should weigh?

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  • Mellouk89Mellouk89 Member Posts: 160 Member Member Posts: 160 Member
    17% is in the healthy range for a male last I checked. I would've been very lean at the higher end of bmi but we aren't talking about being ripped here. We are talking about healthy body fat levels. An average man can be 17% bf at a normal bmi. And the average man is not shredded at a bmi of 25. Dumb argument.

    I didnt bring up the topic of football players, read the damn thread. If you don't want the topic to derail stop quoting and then blame me on the same occasion.

    edited December 2020
  • paperpuddingpaperpudding Member Posts: 6,298 Member Member Posts: 6,298 Member
    I did. I brought up football players. I own that.

    The point of which was to show that real verifiable (as in anyone can google their stats to check) young men who are sporty and muscular are not that far above standard BMI ranges.
    My point in bringing up position was to show I was not cherry picking lean running types.

    However I agree both that and what bf mellouk himself has are irelevant to OP's question.

    Highly highly unlikely a woman wondering if her BMI being outside standard range is not, as the BMI would suggest, overweight.

    How much and how significant that is we don't know without further information from OP.
  • frankwbrownfrankwbrown Member, Premium Posts: 758 Member Member, Premium Posts: 758 Member
    I read a little bit about the history of BMI. I found it interesting that it was developed in the 1830's by a Belgian mathematician, not a physician. It got its name in 1972 in a paper published by Ancel Keys. I believe it was in the 1990's that it was adopted by the WHO.

    The article referenced below hits upon some points that I had been thinking, one of them being that a formula designed to apply to populations will not work as well when applied to individuals. Secondly, while it's true that someone who is extremely overweight will have a high BMI, it is not necessarily true that someone with a high BMI is overweight (we've gone round and round on that one, with many agreeing but saying nevertheless the exceptions are few and understandable). If you read it with an open mind, you'll understand my dislike of BMI. You may not agree, but perhaps you'll understand. In any case, the article serves as my last 2 cents worth on the matter. But I'll happily continue to follow the discussion.

    Ten Reasons Why the BMI Is Bogus

  • frankwbrownfrankwbrown Member, Premium Posts: 758 Member Member, Premium Posts: 758 Member
    No I do not agree nor understand.

    that article seems quite nonsense to me

    things like It suggests there are distinct categories of underweight, ideal, overweight and obese, with sharp boundaries that hinge on a decimal place.

    That's total nonsense.


    Indeed it would be total nonsense - but since nobody is suggesting using BMI like that it is also a total strawman.

    Rest are not much better.

    Tell me how you really feel! :smile:
    You picked the weakest one. I find merit in numbers 1, 2, 8 and 9. There are better methods than BMI. That's all I'm saying.
    And if you can't understand why I would not like BMI despite you liking it, then we'll have to agree to disagree.
    edited December 2020
  • frankwbrownfrankwbrown Member, Premium Posts: 758 Member Member, Premium Posts: 758 Member
    sijomial wrote: »
    ...
    What a simply idiotic article!
    About the only merit in there is that they point out that some people use a simple screening tool in an inappropriate way. A bit like saying a hammer is a bad tool because some people try to use it as a screwdriver.

    The NHS sum up how it can be used, should be used as one of many health assessment tools and its limitations.
    https://www.nhs.uk/live-well/healthy-weight/bmi-calculator/

    Do you think it's possible that, after approximately 190 years, with our current knowledge of the human body and the technology at our disposal, it might be entirely possible to develop a better metric than BMI? One that includes, say, waist circumference (at least) in addition to height and weight? Just sayin'.
  • Theoldguy1Theoldguy1 Member Posts: 1,563 Member Member Posts: 1,563 Member
    sijomial wrote: »
    ...
    What a simply idiotic article!
    About the only merit in there is that they point out that some people use a simple screening tool in an inappropriate way. A bit like saying a hammer is a bad tool because some people try to use it as a screwdriver.

    The NHS sum up how it can be used, should be used as one of many health assessment tools and its limitations.
    https://www.nhs.uk/live-well/healthy-weight/bmi-calculator/

    Do you think it's possible that, after approximately 190 years, with our current knowledge of the human body and the technology at our disposal, it might be entirely possible to develop a better metric than BMI? One that includes, say, waist circumference (at least) in addition to height and weight? Just sayin'.

    For most of the population do you think waist measurement gives a different result than BMI? Agree waist measurement is probably better but also has a bit more measurement issues due to questions such as where to measure, it the person relaxed, etc.
  • frankwbrownfrankwbrown Member, Premium Posts: 758 Member Member, Premium Posts: 758 Member
    ...


    Yes I politely did - I'm not pretending your article is sensible when it is not.
    Are you familiar with the notion of friendly sarcasm? :neutral:
    ...

    and yes no 7, the one I quoted was the most ridiculous - and like I said, rest was not much better

    Its not a matter of me liking it, it is a matter of it being an accepted guideline ,which, when used in context, is relevant for the vast majority of people.

    Other things also being relevant or more advanced technology being available for those who want such, doesnt negate that.

    if you really think BMI is not a good tool, then you would want to present better evidence for that opinion than the article you used.

    That it is relevant for the vast majority of people is immaterial to me. And I am speaking not for everyone but for myself and others like me for which it is not a good tool, precisely because I/we are not among that "vast majority of people". I don't understand what you don't get about that.

    I'm not telling anyone not to use BMI. So, please give it up.
    I disagree with your disagreeing to agree to disagree, I think.

    edited December 2020
  • paperpuddingpaperpudding Member Posts: 6,298 Member Member Posts: 6,298 Member
    well you can give it up if you like - please dont tell me when to stop or continue posting.
    I'll decide that myself..

    Unless there is some obvious outlier reason that applies to you ( eg you are an amputee, a person with dwarfism, 9 months pregnant, an elite body builder) then, yes, BMI charts would apply to you - ie you would be at a healthy weight somewhere in, or at the most slightly out, of the standard range.

    Because human body.

    You dont have to use the tool if you dont want to - but that doesnt change what I said.
  • frankwbrownfrankwbrown Member, Premium Posts: 758 Member Member, Premium Posts: 758 Member
    well you can give it up if you like - please dont tell me when to stop or continue posting.
    I'll decide that myself..

    Unless there is some obvious outlier reason that applies to you ( eg you are an amputee, a person with dwarfism, 9 months pregnant, an elite body builder) then, yes, BMI charts would apply to you - ie you would be at a healthy weight somewhere in, or at the most slightly out, of the standard range.

    Because human body.

    You dont have to use the tool if you dont want to - but that doesnt change what I said.

    I suppose I could diet until I fall in the normal BMI range, even if it kills me. Nah, probably not. But I'm thrilled that you, knowing little to nothing about me, think that BMI would apply to me. (fyi: this is sarcasm)

    Like I said... agree to disagree. But I trust you'll have the last word.
  • paperpuddingpaperpudding Member Posts: 6,298 Member Member Posts: 6,298 Member
    I dont need to know anything about you to know that, unless you are an obvious outlier, like the ones I described, then you will be at a healthy weight somewhere in, or at most slightly out of, standard BMI range.

    because human body.
  • frankwbrownfrankwbrown Member, Premium Posts: 758 Member Member, Premium Posts: 758 Member
    What I've learned here today is that BMI applies to me, unless I am an obvious outlier, in which case it doesn't.
    ... because human body.

    tautology... because logic. :D
  • sijomialsijomial Member, Premium Posts: 17,600 Member Member, Premium Posts: 17,600 Member
    What I've learned here today is that BMI applies to me, unless I am an obvious outlier, in which case it doesn't.
    ... because human body.

    tautology... because logic. :D

    Just curious, do you actually think you are an outlier at age 70+ or is this just a general dislike of BMI?
    If you do think you are an outlier - why?

    Just for comparison in my 20's (until I changed sports to one that favoured being lighter) I considered my best weight was indeed about 7lbs into the BMI overweight range. But I had been strength training for many years by then and responded well to training in terms of hypertrophy. Any medic that assessed me would not have been concerned or advise me to drop weight because it was clear I was fit and strong with an unusually good amount of muscle.

    But when I dieted down from clearly overweight/overfat in my 50's despite an atypical physique for an old fart my best weight did turn out to be in the BMI normal range.
  • AnnPT77AnnPT77 Member, Premium Posts: 18,171 Member Member, Premium Posts: 18,171 Member
    sijomial wrote: »
    What I've learned here today is that BMI applies to me, unless I am an obvious outlier, in which case it doesn't.
    ... because human body.

    tautology... because logic. :D

    Just curious, do you actually think you are an outlier at age 70+ or is this just a general dislike of BMI?
    If you do think you are an outlier - why?

    Just for comparison in my 20's (until I changed sports to one that favoured being lighter) I considered my best weight was indeed about 7lbs into the BMI overweight range. But I had been strength training for many years by then and responded well to training in terms of hypertrophy. Any medic that assessed me would not have been concerned or advise me to drop weight because it was clear I was fit and strong with an unusually good amount of muscle.

    But when I dieted down from clearly overweight/overfat in my 50's despite an atypical physique for an old fart my best weight did turn out to be in the BMI normal range.

    Background admission: I'm female, and narrow-hipped, so no question of being at the top of the normal BMI range at an ideal weight even at reasonable muscle mass (by which I mean any rational muscle mass I believe I could achieve, even had I started young, and tried hard), though being at a healthy weight near the top of BMI range would be possible.

    Main point of my post: I think many people who are significantly overweight** underestimate the reduction in lean mass that will occur with sensible weight loss, even without muscle loss along the way. There's a lot of body-stuff included in lean mass, and some of it we actually need materially less of, at a significantly lower body weight, so the body doesn't prioritize keeping it around. Perhaps even some muscle could be lost, without functional impact, I don't know. Also, I understand that BIA estimates are unreliable.

    I'm working from memory here because I can't put my hands on the datasheets, but IIRC, a BIA device put my body fat percent at around 35%ish when I was class 1 obese, weighing 183 (and around that value for several measurements over a period of time). That would imply 64 pounds of fat, 119 of lean mass (rounded). That's an improbably low BF%, but not totally implausible all factors considered at the time. Now, I'm at 125 pounds, and my BIA scale consistently says around 23% BF. Rounded to whole numbers, that would be 29 pounds of fat, and 96 pounds of lean mass.

    I guarantee I didn't lose 23 pounds of functional muscle mass during that weight loss. My objectively-measured best performance at a sport requiring strength but not penalizing fat stayed about the same, before and after. (Machine rowing, if anyone cares. Statistically, heavyweights are faster, but the reason is not generally understood to be bodyweight per se.)

    So, not only do I agree with you, sijomial, that our bodies at an older age may not be what we'd assume based on a younger age; but also I think one can't make too many assumptions from fat/lean numbers when significantly overweight, as a predictor of healthy bodyweight once sensible loss has taken place.

    ** I'm not taking veiled jabs at any PP here, I'm just extending the conversational sub-threads. If I'm jabbing, the reader will know it. Further, I understand that some scan results include an estimate of muscle mass per se, or of bone mass (which also should not change lots, at least not quickly, but would narrow down what the lean mass is). I don't have any of those results, personally.

    I'm pretty much writing this because I think it's responsive to the thread's general theme of "what metrics help one predict a good goal weight". Personally, I think relying on scan metrics as a predictor, if significantly overweight at the start, may not be all that helpful. I'm no expert, though.
  • AnnPT77AnnPT77 Member, Premium Posts: 18,171 Member Member, Premium Posts: 18,171 Member
    AnnPT77 wrote: »
    Theoldguy1 wrote: »
    Have you compared a DEXA scan to the Withings scale? We have an older scale and it isn't worth the powder to blow it to hell regarding getting a reading similar to DEXA scan.
    Yes. Here is a comparison:

    A = Withings Body+ (9/30 at 6:10 am);
    B = DEXA scan (9/30 at 11:30 am)
    body fat: A = 49% , B = 44.5%
    weight (lb): A = 304.9, B = 305.0
    fat mass (lb): A = 150.8, B = 135.6
    lean mass (lb): A = 154.1, B = 169.4 (159.9 excluding bone mass)
    water mass (lb): A = 125.8, B = n/a
    bone mass (lb): A = 7.6, B = 9.5
    BMI: A = 40.4

    Bioelectrical impedance isn't that accurate, especially when only feet are involved (vs feet and hands).
    I use it primarily to confirm that I'm losing fat mass and not lean mass.

    Some doctors at Cedars-Sinai developed an alternative to BMI. It's called Body Fat Mass Index.
    Relative Fat Mass Index:
    Men: 64 – (20 x height/waist circumference) = RFM
    Women: 76 – (20 x height/waist circumference) = RFM
    https://www.cedars-sinai.org/blog/relative-fat-mass.html

    So - since we've digressed the bejeepers out of this thread already - why not: What result does the RFM calculation yield, for you?

    I'm curious, because the result it gives for me - especially if I measure my "waist" at just above the top of my pelvic bones as directed in the article, rather than at natural waist - is . . . improbable, IMO. I understand that the article says RFM is "roughly equal to your body fat percentage." Maybe they define "roughly" differently than I do?

    I'm as capable as the next person of having pleasant delusions about my body composition, but the "Navy calculator" says 23%, BIA scale says 23.3%, visual (my own biased eyes, photos like those on an earlier page in the thread) would be mid-twenties % (high teens upper body look, 25-30 lower body look, roughly), BMI 20.6.

    RFM, using natural waist = 29. (OK, maybe that's roughly roughly. Very roughly.)
    RFM, using top of hip bone as instructed in article = 34. Huh?

    I'm not truly bizarre in body geometry, either, I swear. Definitely within the range of normal human females.

    So, since I didn't see an answer to this, I'll extend the question to others: Did *anyone* else try the RFM calculator?

    https://www.cedars-sinai.org/blog/relative-fat-mass.html

    If so, did it produce a number "roughly equal to your body fat percentage", or what you believe that percentage to be?

    I'm curious, that's all.
  • lemurcat2lemurcat2 Member, Premium Posts: 6,502 Member Member, Premium Posts: 6,502 Member
    AnnPT77 wrote: »
    AnnPT77 wrote: »
    Theoldguy1 wrote: »
    Have you compared a DEXA scan to the Withings scale? We have an older scale and it isn't worth the powder to blow it to hell regarding getting a reading similar to DEXA scan.
    Yes. Here is a comparison:

    A = Withings Body+ (9/30 at 6:10 am);
    B = DEXA scan (9/30 at 11:30 am)
    body fat: A = 49% , B = 44.5%
    weight (lb): A = 304.9, B = 305.0
    fat mass (lb): A = 150.8, B = 135.6
    lean mass (lb): A = 154.1, B = 169.4 (159.9 excluding bone mass)
    water mass (lb): A = 125.8, B = n/a
    bone mass (lb): A = 7.6, B = 9.5
    BMI: A = 40.4

    Bioelectrical impedance isn't that accurate, especially when only feet are involved (vs feet and hands).
    I use it primarily to confirm that I'm losing fat mass and not lean mass.

    Some doctors at Cedars-Sinai developed an alternative to BMI. It's called Body Fat Mass Index.
    Relative Fat Mass Index:
    Men: 64 – (20 x height/waist circumference) = RFM
    Women: 76 – (20 x height/waist circumference) = RFM
    https://www.cedars-sinai.org/blog/relative-fat-mass.html

    So - since we've digressed the bejeepers out of this thread already - why not: What result does the RFM calculation yield, for you?

    I'm curious, because the result it gives for me - especially if I measure my "waist" at just above the top of my pelvic bones as directed in the article, rather than at natural waist - is . . . improbable, IMO. I understand that the article says RFM is "roughly equal to your body fat percentage." Maybe they define "roughly" differently than I do?

    I'm as capable as the next person of having pleasant delusions about my body composition, but the "Navy calculator" says 23%, BIA scale says 23.3%, visual (my own biased eyes, photos like those on an earlier page in the thread) would be mid-twenties % (high teens upper body look, 25-30 lower body look, roughly), BMI 20.6.

    RFM, using natural waist = 29. (OK, maybe that's roughly roughly. Very roughly.)
    RFM, using top of hip bone as instructed in article = 34. Huh?

    I'm not truly bizarre in body geometry, either, I swear. Definitely within the range of normal human females.

    So, since I didn't see an answer to this, I'll extend the question to others: Did *anyone* else try the RFM calculator?

    https://www.cedars-sinai.org/blog/relative-fat-mass.html

    If so, did it produce a number "roughly equal to your body fat percentage", or what you believe that percentage to be?

    I'm curious, that's all.

    No, it's quite a bit off for me, including using the numbers I had when I had a Dexa.
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