BMI is an utterly bogus means of determining individual fitness assessments, and there's some reason to believe it's not very useful for population measures of fitness.
Dude, thanks for linking to Dr. Keith Devlin's column. Probably the only thing I read religiously in the MAA.
BMI is just one of several mistakes attributed to the great mathematician Quetelet. You can credibly implicate Quetelet for a variety of modern day statistical crimes such as profiling ( attempting to figure out if a person is a criminal based on statistical analysis of race/sex/height/etc...),"normal" age of marriage, statistical rates of divorce in different countries and their implications on fidelity, and such other sociological nonsense.
Dr. Devlin labels these things "junk math, numerological nonsense". But you can take a more charitable view - given that Quetelet practically invented both statistics & sociology ( which he called "physics of society" ), he came up with a number of formulae that seemed true at that time ( mid 1800s ). On hindsight much of this stuff is just silly mathematical manipulation ( Instead of dividing weight by square of height & multiplying by the constant 703, you can square the weight & divide by the cube root of height and put in some other constant...)
If you are interested in the kind of statistics practiced in Quetelet's timeframe, here's some wacky references.
btw, much of what we do today in quant finance is suspiciously similar to what Quetelet suggests :) We build statistical "factor models" that credibly relate earnings of a company in california to the price of chicken in China :) We take a rigged number called the LIBOR & price interest rate derivatives on the spead between this rigged fixed rate & the floating rate. Then the public loses money & we scream - hey who the fuck rigged the LIBOR in the first place ?:) Talk about bootstrapping... honestly, we are no different from Dr. Quetelet. Might as well base Google's quarterly earnings on Page's BMI.
I'm really not a fan of BMI being the determining factor in obesity. At 27 BMI, I'm apparently 3 BMI away from being considered obese. As a naturally large, fairly muscular 24 year old german/irish man, I'm 6 foot 1 and weigh 205 lbs, but you can see my abs and I'm in relatively good physical condition. Is my definition of obese wrong? I always thought obese meant someone with at least a few dozen lbs of excess fat.
Invent a way of easily measuring body fat percentage, and we can do away with BMI. Until then, muscular people can simply ignore these things. BMI works well enough for the rest of the population (the vast majority of the world). If anything, normal people have the opposite problem you do. BMI tends to underestimate obesity in the general population. http://www.cnn.com/2012/04/03/health/obesity-rates-maybe-wor...
Before complaining about "wah wah that's BMI, BMI sucks" please think twice. Everybody knows it's BMI, BMI is a rough measurement of your ratio height to weight.
"The medical establishment has acknowledged major shortcomings of BMI.[...] found that BMI-defined obesity was present in 21% of men and 31% of women. Using body fat percentages (BF%), however, BF%-defined obesity was found in 50% of men and 62% of women."
Take it as a statistical game and stop getting self conscious about it.
Note also: If you are very muscular with a crazy BMI despite no fat it's not healthy either.
Note also: If you are very muscular with a crazy BMI despite no fat it's not healthy either.
I hear this claim parroted quite a bit. I haven't seen any evidence of this in medical literature, though, except in cases of really big guys like NFL lineman. Do you have any references for the claim?
No "everyone" doesn't know that BMI is discredited, the BBC should have put a huge disclaimer on it saying "these numbers are nothing to do with how healthy you are, in fact they are completely meaningless".
I was really interested to see this data until I saw that they use the BMI; possibly the dumbest and most loudly touted measure of health. According to these numbers I am overweight, heading towards obese, and I don't think any doctor on Earth would say I was overweight if they looked at me.
By moving to a city with a lot of S.E. Asian people I'm suddenly above average BMI - I need to move back to Texas.
On the other hand, all those little old Japanese women mean that the average life expectancy here is among the highest in the world - so I should live to a 100 like them
[+] [-] dredmorbius|13 years ago|reply
- Top 10 Reasons Why The BMI Is Bogus : http://www.npr.org/templates/story/story.php?storyId=1062684...
- Beyond BMI, Why doctors won't stop using an outdated measure for obesity : http://www.slate.com/id/2223095/
- Do You Believe in Fairies, Unicorns, or the BMI? : http://www.maa.org/devlin/devlin_05_09.html
[+] [-] dxbydt|13 years ago|reply
BMI is just one of several mistakes attributed to the great mathematician Quetelet. You can credibly implicate Quetelet for a variety of modern day statistical crimes such as profiling ( attempting to figure out if a person is a criminal based on statistical analysis of race/sex/height/etc...),"normal" age of marriage, statistical rates of divorce in different countries and their implications on fidelity, and such other sociological nonsense.
Dr. Devlin labels these things "junk math, numerological nonsense". But you can take a more charitable view - given that Quetelet practically invented both statistics & sociology ( which he called "physics of society" ), he came up with a number of formulae that seemed true at that time ( mid 1800s ). On hindsight much of this stuff is just silly mathematical manipulation ( Instead of dividing weight by square of height & multiplying by the constant 703, you can square the weight & divide by the cube root of height and put in some other constant...) If you are interested in the kind of statistics practiced in Quetelet's timeframe, here's some wacky references.
http://en.wikisource.org/wiki/Popular_Science_Monthly/Volume...
http://statistiks.net/wp-content/plugins/downloads-manager/u...
btw, much of what we do today in quant finance is suspiciously similar to what Quetelet suggests :) We build statistical "factor models" that credibly relate earnings of a company in california to the price of chicken in China :) We take a rigged number called the LIBOR & price interest rate derivatives on the spead between this rigged fixed rate & the floating rate. Then the public loses money & we scream - hey who the fuck rigged the LIBOR in the first place ?:) Talk about bootstrapping... honestly, we are no different from Dr. Quetelet. Might as well base Google's quarterly earnings on Page's BMI.
[+] [-] tfb|13 years ago|reply
[+] [-] streptomycin|13 years ago|reply
[+] [-] evilmushroom|13 years ago|reply
This is going to tell me I'm fat.
[+] [-] graeme|13 years ago|reply
I hovered around 25 BMI, was muscular, thought it was silly. Everyone considered me "lean". But, no abs.
Now I can see mine, am very strong, and have a 23 BMI.
It's possible BMI effectiveness changes with height though, which would make it even worse. I'm 5'6".
[+] [-] scott_s|13 years ago|reply
[+] [-] gaius|13 years ago|reply
I'm a Marathon runner who is apparently fatter than 99% of the world...
[+] [-] jere|13 years ago|reply
But whether you're muscular or fat, this scale is a pretty good reminder of how well nourished we are compared to everyone else.
[+] [-] mithras|13 years ago|reply
"You're most like someone from DR Congo"
[+] [-] graeme|13 years ago|reply
They clearly mean I'm heavier than most people, but lighter than the average BMI. Very large people skew the average upwards.
Edit: I am wrong. See the comment below. I thought average referred to arithmetic mean.
[+] [-] dredmorbius|13 years ago|reply
You're messing up "average" and "mean" :)
[+] [-] victork2|13 years ago|reply
http://en.wikipedia.org/wiki/Body_mass_index#Limitations_and...
"The medical establishment has acknowledged major shortcomings of BMI.[...] found that BMI-defined obesity was present in 21% of men and 31% of women. Using body fat percentages (BF%), however, BF%-defined obesity was found in 50% of men and 62% of women."
Take it as a statistical game and stop getting self conscious about it.
Note also: If you are very muscular with a crazy BMI despite no fat it's not healthy either.
[+] [-] vonmoltke|13 years ago|reply
I hear this claim parroted quite a bit. I haven't seen any evidence of this in medical literature, though, except in cases of really big guys like NFL lineman. Do you have any references for the claim?
[+] [-] gaius|13 years ago|reply
[+] [-] mathewsanders|13 years ago|reply
[+] [-] Tooluka|13 years ago|reply
[+] [-] cryptide|13 years ago|reply
[+] [-] thekungfuman|13 years ago|reply
[+] [-] excuse-me|13 years ago|reply
By moving to a city with a lot of S.E. Asian people I'm suddenly above average BMI - I need to move back to Texas.
On the other hand, all those little old Japanese women mean that the average life expectancy here is among the highest in the world - so I should live to a 100 like them