Among adults, I guarantee you there is an inverse relationship between BMI and sprint times.
I made the statement about my own 100m sprint time to characterize my own level of fitness beyond the crude BMI. Sprint times define fitness as a function of mass and muscle.
My point is that I am classified as overweight by BMI at 6’ 195lbs, yet I have a 32in waist and can sprint faster than 95%(bs retorical stat) of the population.
Specifically, I’ve heard that excess weight, whether muscle or fat, stresses the skeletal system and joints; also that it taxes the cardiovascular system to supply blood and oxygen to all that body mass.
I brought it up here because I’ve only ‘heard’ it – in various articles and some messageboards. Maybe even on the SDMB. I thought somebody might know offhand whether it was true or not. But it looks like I’m going to have to do some research. If I’ve heard it, that means others have; so even if it isn’t true I should be able to find some refutation somewhere.
Well, the BMI index is rather outdated. (Read all three pages of the study I link in that post.) What really needs to be considered is the amount of what they call visceral fat, which is not obvious by looking at a person, a round person can have very little, and a skinny person with a gut can have a lot and be at great risk. ETA: So, the location of the fat, as well as how much of that kind of fat there is, is a more important consideration when evaluating the person’s health risks.
BMI is a great tool to use when you need to roughly, yet objectively, guage a thousand folks for a study. Applying it to individuals at a doctor’s office… completely retarded. The doctor will be much more accurate just looking at your ass to tell you whether you’re fat and unhealthy than by following the BMI. Scientific studies can’t have such subjectiveness, but a doctor eyeing you up and down will easily account for how muscular you are, etc. I think the real point is that by using the BMI, the doctor can feel like it’s the chart that’s calling you fat, not him. Small distinction, but probably of significant psychological importance.
Er, what I meant to say was: Scientists use BMI because they have to. It’s completely objective, and it’s cheap. Objectivity is a be-all-end-all to a research scientist, but objectivity doesn’t really equal accuracy. Objectivity just means someone can’t come up and accuse you of things that you’ll have no way of disproving. So research scientists demand objectivity at all costs, even thought it actually would be more accurate to look at a person to see if he’s fat. Calipers or other techniques might be even more accurate while also being fully objective, but if the only choices, for reasons of cost, are BMI and looking, then research scientists should pick BMI and doctors at a doctor’s office should just look.