My 1,000 word essay on why BMI isn't useful for a sample size of 1

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  • hipari
    hipari Posts: 1,365 Member
    Leaving aside OP's chart - because I am not a graph person and I dont really understand what it is saying and it has obvious inaccuracies if it includes subjects with 0% body fat

    I dont get the antagonism either.

    BMI is a useful guide for the vast majority of people - and for those who are genuine outliers, this is obvious both to themselves and their doctors.

    Does anyone really not know, or think a doctor would not see, that they are an elite body builder or an amputee or a person with dwarfism or 9 months pregnant or have a huge instestinal tumour or any other reason why standard BMI calculations would not apply to them??

    So, sure, in OP's words, BMI is not a useful number for those n = 1 people.

    No kidding.


    My own n=1 - as a not very muscular middle aged woman with a BMI of 28 - both my doctor and myself and any casual observer could tell it wasnt an abnormal amount of muscle or a medical condition - I was plain old over weight.
    am healthier now and less likely to develop weight related medical conditions, with a BMI of 23.

    Agreed. BMI is a model that measures people, not math that can be proven in absolute terms. "Healthy" or "unhealthy" is not a binary, it's a model that gives guidelines that are relevant to most people. Since "healthy" isn't binary, there's not really a definite limit between "normal weight" and "overweight", those are constructs created as guidelines as well.

    My own n=1: My current BMI is 33 and there is no question that I am overweight/obese. However, all body composition measurements I've taken (multiple), health professionals' estimations and my past experience indicate that my "ideal" or "healthy" weight would likely be at BMI 25-26, which would still make me overweight according to BMI charts. While in that case BMI wouldn't be exactly "correct" in that sense, there's no question in my mind that it's a good indicator of which direction I should take.
  • paperpudding
    paperpudding Posts: 9,515 Member
    Hipari - yes I agree. The BMI chart is a spectrum not an absolute Yes or No cut off.

    we sometimes see threads where people are saying I am fit, I go to the gym, I have lost weight but I cant get my BMI below 25.1 - as if somehow 24.9 and 25.1 were some massive difference and that 0.1% is going to change everything.


    But, barring obvious outliers, examples as in my post above yours, the vast majority of people can be sure 33 is not a healthy BMI for them.


    However, as I have stated on these threads before, there are sporty muscular young men who are quite healthy slightly above the official cut off point - ie with a BMI of around 26 -28

    Not elite body builders - just fit sporty young men.

    Again I was a not so fit 50 year old woman, not a sporty muscular young man - and I didnt need a doctor or a chart to tell me that the exceptions of 28 being upper end of healthy did not apply to me.



  • hipari
    hipari Posts: 1,365 Member
    @paperpudding exactly. I’m fairly muscular (under the fat), with a large frame, wide pelvis (hip bones) and big boobs, so putting a healthy fat percentage on top of all that easily leads to a BMI that’s slightly over 25. From BMI 33 it’s pretty clear that there’s only one direction, but the distance to ”healthy” can’t be defined on exact terms.

    BMI is a great indicator, not an absolute truth.
  • bmeadows380
    bmeadows380 Posts: 2,981 Member
    I was one of those who was against the BMI for years until I finally got a grasp of what the BMI was saying and that it was a statistical average and was really communicating risk of health problems. I think it comes in to a common misunderstanding and miscommunication of the point behind the number for a given person - the common perception is that if you are above a 25, then you have to be "unhealthy" no matter how active or fit you really are. And medical doctors for a long time pushed that number; nowadays they seem to be getting away from using it as a hard and fast rule, or at least, its seems that way in my experience. I'm hearing a lot more advice on losing 5% of your current weight and not so much on the BMI number. Not sure about the insurance companies, though.

    For me personally, I seriously doubt I'll ever make it to that magical 25 BMI; I"m getting older and I don't think I have the patience or the fortitude it takes to be super tight on your logging to lose those last 10-15 lbs. I can live with being in the "overweight" category; its still worlds healthier and a much better risk profile than what I had when I was stage III obese.
  • NorthCascades
    NorthCascades Posts: 10,968 Member
    Leaving aside OP's chart - because I am not a graph person and I dont really understand what it is saying and it has obvious inaccuracies if it includes subjects with 0% body fat

    I dont get the antagonism either.

    BMI is a useful guide for the vast majority of people - and for those who are genuine outliers, this is obvious both to themselves and their doctors.

    Does anyone really not know, or think a doctor would not see, that they are an elite body builder or an amputee or a person with dwarfism or 9 months pregnant or have a huge instestinal tumour or any other reason why standard BMI calculations would not apply to them??

    So, sure, in OP's words, BMI is not a useful number for those n = 1 people.

    No kidding.


    My own n=1 - as a not very muscular middle aged woman with a BMI of 28 - both my doctor and myself and any casual observer could tell it wasnt an abnormal amount of muscle or a medical condition - I was plain old over weight.
    am healthier now and less likely to develop weight related medical conditions, with a BMI of 23.

    Just a guess, but I think this (the OP) sets peoples' BS detectors off.
  • Mellouk89
    Mellouk89 Posts: 469 Member
    I think waist measurement is a better indicator, at least for men. If you don't trust the BMI chart, measure your waist and find out if it's ok relative to your height.
  • paperpudding
    paperpudding Posts: 9,515 Member
    Why would you not trust the BMI chart??

    Or more correctly, using the BMI chart in context ??
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