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In that case BMI gets misused a lot. The bashing comes because whilst it may be useful on a large statistically significant population it is nearly useless at a

In that case BMI gets misused a lot. The bashing comes because whilst it may be useful on a large statistically significant population it is nearly useless at an individual level. One can take two people of identical BMI and one can be actually very fat and the other very slim.

paulojreis 11y ago
Misused, by whom? I trust my physician to know how to interpret the BMI values. I don't trust my insurance company to do the same, but they're eventually the ones with a large n (so to speak) - ethics aside, if they want a cost-effective way to factor obesity in their premium, BMI might be the way to go. They'll overestimate the premium for the bodybuilder, but they'll get right most of the time. I'd expect most misuse to be by the media and random people in the Internet. In both cases, however, you should already be taking everything - not only BMI stuff - with a grain of salt. P.S. Even at an individual level, BMI will hold true for the large majority. Even you're talking in a fitness forum, most people won't have enough muscle mass to affect the index that much.
- heynk 11y ago
  I know a guy who is a hardcore triathlete. At one point a few years ago he was doing really well, sponsored athlete, over 210 pounds with only 7% body fat. He was at a regular check up and the nurse looked at the BMI chart, then looked at him and plainly said 'Maybe you should work out more'. Just my anecdata that BMI is misused even in the medical community.
  - JoeAltmaier 11y ago
    Talking about clueless - had a back issue, physical therapist gave me some good exercises. I asked "In winter I get soft, cycle all summer but with snow I need something else. I hate spin classes. What should I do?" She gave me a dozen reps with a rope on my ankle, 4 lbs weight. Now, 20 miles in a short ride is what, about 4000 reps, at quite a bit more than 4lbs. I mentioned this. She said "Lets just start out at 4 lbs and work up slowly". Sometimes I just wonder.
douche 11y ago
The fact that it takes into account just height and weight is problematic. No consideration of bone structure or body frame. At my absolutely lightest, when you could see every rib sticking out, my BMI was still comfortably in the range considered overweight. If I were to live through the Bataan death camps, I might get down to skin and bone enough to be in the normal range.
- paulojreis 11y ago
  > The fact that it takes into account just height and weight is problematic. No consideration of bone structure or body frame. That's a bug, not a feature, if you allow me to grab the expression from software. It's problematic as any other indicator has "problematic" features. My point being: when you assess any indicator, you can't look only at it's ability to correctly reflect reality (validity). You'll also have to consider other stuff: is it cheap? can I trust people to use it correctly? can it be used consistently? Taking into account only height and weight will diminish validity, but give you positive answers to these three questions. It's a trade-off (and, IMHO, one that's being bashed excessively, considering the empirical evidence saying it's not that "invalid" at all). Compare it with e.g. skinfold estimation of body composition: skinfold estimation is more valid, yet science shows us that it requires a highly trained specialist for it to be reliable (i.e. to do it consistently; and even with professionals, there's not much consistency). This is also problematic, but - again - it's a bug, not a feature. > At my absolutely lightest, when you could see every rib sticking out, my BMI was still comfortably in the range considered overweight. ... and that's you being an outlier, or close. :) I'm one as well; also overweight, by BMI standard. But I have to consider that my care with nutrition and fitness should also be close to outlier in nature, regarding population in general. Knowing this, you and I (and our physicians) will take it into account. And - if the need arises - use another metric. I do both skinfold estimation of body composition and waist circumference measurement but rely mostly on the latter for tracking progress (I'm not a professional and, of course, it's me measuring myself, so I choose the method where I might mess up less).
  - douche 11y ago
    I'm not so sure that I'm really an outlier, to be honest. I think the data that the BMI calculations are based on is outdated. It's the same numbers you see from New York Life actuarial tables from the 40s and 50s, when big chunks of the population experienced malnutrition. Quite honestly, I have no idea how someone could be 6'2" and only weigh 148 pounds, which is the bottom end of "normal" BMI, according to the NIH[1]. [1] http://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmi_tbl.htm http://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmi_...

paulojreis 11y ago

Misused, by whom? I trust my physician to know how to interpret the BMI values. I don't trust my insurance company to do the same, but they're eventually the ones with a large n (so to speak) - ethics aside, if they want a cost-effective way to factor obesity in their premium, BMI might be the way to go. They'll overestimate the premium for the bodybuilder, but they'll get right most of the time. I'd expect most misuse to be by the media and random people in the Internet. In both cases, however, you should already be taking everything - not only BMI stuff - with a grain of salt. P.S. Even at an individual level, BMI will hold true for the large majority. Even you're talking in a fitness forum, most people won't have enough muscle mass to affect the index that much.

heynk 11y ago
I know a guy who is a hardcore triathlete. At one point a few years ago he was doing really well, sponsored athlete, over 210 pounds with only 7% body fat. He was at a regular check up and the nurse looked at the BMI chart, then looked at him and plainly said 'Maybe you should work out more'. Just my anecdata that BMI is misused even in the medical community.
- JoeAltmaier 11y ago
  Talking about clueless - had a back issue, physical therapist gave me some good exercises. I asked "In winter I get soft, cycle all summer but with snow I need something else. I hate spin classes. What should I do?" She gave me a dozen reps with a rope on my ankle, 4 lbs weight. Now, 20 miles in a short ride is what, about 4000 reps, at quite a bit more than 4lbs. I mentioned this. She said "Lets just start out at 4 lbs and work up slowly". Sometimes I just wonder.

douche 11y ago

The fact that it takes into account just height and weight is problematic. No consideration of bone structure or body frame. At my absolutely lightest, when you could see every rib sticking out, my BMI was still comfortably in the range considered overweight. If I were to live through the Bataan death camps, I might get down to skin and bone enough to be in the normal range.

paulojreis 11y ago
> The fact that it takes into account just height and weight is problematic. No consideration of bone structure or body frame. That's a bug, not a feature, if you allow me to grab the expression from software. It's problematic as any other indicator has "problematic" features. My point being: when you assess any indicator, you can't look only at it's ability to correctly reflect reality (validity). You'll also have to consider other stuff: is it cheap? can I trust people to use it correctly? can it be used consistently? Taking into account only height and weight will diminish validity, but give you positive answers to these three questions. It's a trade-off (and, IMHO, one that's being bashed excessively, considering the empirical evidence saying it's not that "invalid" at all). Compare it with e.g. skinfold estimation of body composition: skinfold estimation is more valid, yet science shows us that it requires a highly trained specialist for it to be reliable (i.e. to do it consistently; and even with professionals, there's not much consistency). This is also problematic, but - again - it's a bug, not a feature. > At my absolutely lightest, when you could see every rib sticking out, my BMI was still comfortably in the range considered overweight. ... and that's you being an outlier, or close. :) I'm one as well; also overweight, by BMI standard. But I have to consider that my care with nutrition and fitness should also be close to outlier in nature, regarding population in general. Knowing this, you and I (and our physicians) will take it into account. And - if the need arises - use another metric. I do both skinfold estimation of body composition and waist circumference measurement but rely mostly on the latter for tracking progress (I'm not a professional and, of course, it's me measuring myself, so I choose the method where I might mess up less).
- douche 11y ago
  I'm not so sure that I'm really an outlier, to be honest. I think the data that the BMI calculations are based on is outdated. It's the same numbers you see from New York Life actuarial tables from the 40s and 50s, when big chunks of the population experienced malnutrition. Quite honestly, I have no idea how someone could be 6'2" and only weigh 148 pounds, which is the bottom end of "normal" BMI, according to the NIH[1]. [1] http://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmi_tbl.htm http://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmi_...