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Thread: BMI - A flawed concept?

  1. #1

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    Question BMI - A flawed concept?

    linkage!



    What do you think? I've never really believed the whole BMI thing, and I hear that the BMI calculator was actually invented by an insurance company, for the purposes of eliminating people they didn't want to insure by making as many people abnormal as possible.

    Opinions?

  2. #2

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    I think that BMI is a guide only based on averages and statistics. I haven't heard the rumour about the insurance compnay.

    I don't think I'm ever going to have a BMI under 25 - just my bone structure and how much muscle I have. I have read that some elite athletes have a BMI of over 30! Maybe fat % is what everyone should be worried about...but that is hard to accurately measure I've been told.

  3. #3

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    I find it a bit strange that men and women both use the same formula with BMI calculation.
    I think every measure is a bit flawed though. I know the skin fold test is - my brother was a very good comeptitive swimmer, very fit etc and when they did the skin fold test on him they had to do his twice becuase the reading was obese, when he quite obviously was not.

    Even the waist measurement thingy with women supposedly needing to be 80cm or under.
    ATM my bmi is around 23, but my waist is 81 and really even when I lose the extra 5 kilos, I doubt my waist measurement is going much lower than 79.

    Theres no right formula for everyone, I think the BMI was supposed to suit a lot of people, and I know that they use it in the defence force too.

  4. #4

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    and the police....which is a buggar cos they use the fat test too where they pinch your fat bits. When i left the accedemy I weighed 54kgs. I am 165cm tall. I had less than 20cm of fat on the pinch test. I was grossly underweight. My BMI was under 21. However - to their credit I had to put on 2 kgs to get to the 54kg before they would let me attest. 12 months later I weighed 60kg and got over 100cm on the fat test.....it can't have been 5kg of pure fat.
    Very flawed.

    I also was there with a guy who's BMI was 44 - they weren't going to let him attest. He was however a state sprinter and was a weightlifter - he could leg press a tonne (1000kg)

  5. #5

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    My hubby constantly weighs in at 'obese' on the BMI however it's all muscle with him, so clearly that is flawed. I've read that better indicators of health outcomes are the actual waist measurement, it has more to do with the kind of fat that predisposes you to diabetes, high blood pressure and heart disease than actual weight for height.

  6. #6

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    the rumor about bmi's being made up by exclusive insurance companies sounds like a load. Its one of those averages things. Averages don't necessarily apply to 100% of everyone- that's why they're called averages. If you maintain a healthy, active lifestyle and you feel good about yourself who the heck has a right to tell you that you must fall between this or that number whether that's a BMI or a number on a scale. They can p1ss off.

  7. #7
    paradise lost Guest

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    BMI was developed in the 1840's for the field of social physics. It was meant to be an epidemiological scale to look at the health of populations. Because most populations will have a small number of anorexics, athletes and bodybuilders it is actually useful for what is was designed for. Unfortunately it is less useful when applied to an individual because it is a tool for looking at population trends.

    It is useful in that it can provide risk factors for averages - for instance having a BMI over 40 is called morbid obesity because there is a strong chance that the person will have morbidity (symptoms) related directly to their weight. And being between 18.5 and 25 for AVERAGE people (not pregnant people, or bodybuilders or many athletes) is associated with least weight-related risk to health.

    It's best to take BMI, as with anything else, with a pinch of salt. If you are working out regularly, are healthy (no high BP, type 2 diabetes etc.), eating a good diet, and are still out of the "normal" BMI catergory it probably doesn't mean anything much. Most of us know if we're honest with ourselves when there is a problem and when there isn't. Not that many athletes will look at their BMI and think "oh gosh, i need to lose weight" because just to BE an athlete you are so aware of diet and exercise. Equally there will be some people with a BMI of 21 who are actually carrying a relatively high % of fat because they eat badly and never exercise and just happen to have a metabolism that stops them getting very heavy.

    It can actually happen that anorexics go into hospital and have high % body fat because when you crash diet your body uses the fastest-to-access energy supply - your muscles. So they might only weigh 30kg but 9kg (30%) is fat because they have almost no lean mass left at all. Typically people in that state are very weak and can barely stand up because their bodies have used all the muscle just to stay alive.

    FWIW for me to qualify as a normal runner in an american road race (rather than an athena, the catergory for heavier female runners) i would have to have a BMI of 19.5. As it is i am healthy and can run and my BMI is 23.7-24.1, and i have no desire to be lighter.

    It might be worth knowing that the link provided is from the site of a man whose daughter was misdiagnosed as anorexic and as such is a fairly biased view.

    Bx

  8. #8

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    Good post hoobley.

  9. #9

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    When DH applied for the Air Force they said his BMI was just above average and that he should lose 5-10kg. But no matter what he did, he could not. He was going to the gym every day. He went back and they said his BMI was even higher. They said he needed to lose more (they still accepted him though) but he couldnt because he had more muscle than fat which is heavier than fat. He is an average person and it does not work for him. So i think the defence force and police academy etc need to wake up to this that is just does not work for everyone. I mean imagine someone like one of those huge footballers going to apply for the defence force. I know that some of them have a BMI of 35 and over! But they dont look like they have any fat on them! I doubt they are going to be turned down for that fact. It's rediculous!

    *off my soap box now*

  10. #10

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    Havent read all the posts so i apologise if i am repeating others.

    BMI (based on weight) is flawed as it doesnt take into account things such as bone density and muscle distrubution....

    Just the same as labelling a weight as obese or bariatric (the medical term that is use for the really really over weight people).
    I authored a hospital policy for Bariatric patients and found that a lot of places were saying that a patient over the weight of 150kg was technically Bariatric (we have not used a weight in our definition). Whilst a lot of people at this weight are very overweight, there are a minority of very tall muscle bound blokes that are this size but are certianly far from far or overweight.

    I believe that if you are really serious about these things tests using calipers to measure body fat are far more effective (although so what humiliating!!!)

    I too am a heavy person often weighting the same as a size 14 or 16 person, but comfortably fitting into 10-12's. when i excercise i put on muscle quickly and thus rarely loose 'weight' but certainly change shape.

  11. #11
    paradise lost Guest

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    Antheia that's crazy! THe American Navy do a caliper skinfold test on anyone, either sex, who has a BMI over what they consider acceptable, and never turn down purely on weight - they WANT strong muscular types! I can't believe they just kept weighing him and didn't do a bodyfat analysis.

    Some of it is down to bodytype (somatotype). You get ectomorphs, mesomorphs and endomorphs.

    Ectomorphs tend to be small and light and do not gain fat or muscle easily. Many top-class runners are ectomorphs. The body tends to be shortish with long limbs and slim, athletic look.

    Mesomorphs tend to be hourglass (women) or rectangular (men) in shape and have large heavy bones and a high proportion of muscle mass. They look athletic, but heavier. Tennis players are a good example, or rowers, big sturdy bodies but hardly any fat.

    Endomorphs tend to be apple (men, sometimes women) or pear (women) shaped and gain fat easily as they have a naturally efficient digestive system and higher number of fat cells. They are better suited to endurance swimming-type events. David Wallaims (the Little Britain comedian, who has also swum the english channel) is an endomorph.

    None of those are absolutes. I'm an endomorph but when i'm slim (i.e. when i'm carrying the right amount of weight for my body) i look a bit more mesomorphic (hourglass), and once i HAVE the extra muscle i find it easier to keep my fat %age down, though i do have to continually work at it. My DP is a mesomorph - he eats MASSES and can gain fat but he only has to LOOK at weights and his muscles grow. His thighs are to die for, OMG, the spin classes and bodypump have made them huge.

    The somatotype is considered to be outdated in physiology because some silly people did studies to see if certain types were more likely to be suicidal or criminals (and drew mainly blanks or at least got questionable results) but i still look around my gym and see these body types.

    Being endomorphic doesn't mean one will be fat, though it is easier for us to gain fat than for an ectomorph, ectomorphs CAN get fat if they work at it. My Bodypump classes are taught by two women, Sharon is an Endomorph and VERY fit, carries a bit of weight but is in no way fat and is VERY powerful, and Leanne is an ectomorph, tiny, light and lifts her OWN WEIGHT for the squat track, even though to look at her thighs you'd think she only does distance running as she's so lean, but there she is lifting masses several times every week.

    I think it can be useful to know because it helps us with aptitudes. Like i enjoy my running and like to run, but i know it's unlikely i'll ever be any kind of running athlete - i doubt i could get sub 50minutes for a 10k without a LOT of prefessional type training. Put me in a pool however and i can really tear it up even when i'm out of shape. When i first learned about the somatotypes i felt annoyed as it's hard to hear "it will always be easiest for you to gain fat" but now i try to see it as my body is the most adaptable. Yeah, sure, i gain fat easily, but i have a lot of endurance for all that and i CAN gain muscle if i work at it. If i were a horse people would be FIGHTING over me - a horse that can perform moderately well for a LONG time on only hay...? Amazin! LOL

    Bx
    Last edited by paradise lost; February 6th, 2008 at 08:24 PM. Reason: spelling

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