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by coldpie 3554 days ago
BMI is a perfectly valid first-order approximation of appropriate weight ranges for the 95% of the population who are not body builders.
2 comments

Perhaps BMI isn't very accurate for slightly short people. It says I should weigh 115-149 lbs. I currently weigh 190 and when I manage to get down to 170, I look very athletic. The last time I weighed 149, I looked like I was starving.

It seems similarly unreasonable for most of my friends and family.

Your standards are based on living in a society of fat people. At 149 you'd still be sporting copious amounts of flab.
My standards are based on objective reality and a decent knowledge of physical fitness and nutrition.

When I weighed 160, I had slightly defined abs. Similar to what you would see on someone with 10-15% body fat.

The existence of a lot of overweight people in the US doesn't change what the words "overweight" and "athletic" mean.

First you looked "very athletic" at 170, now your abs were "slightly defined" at 160. Uh huh. If that means anything, that means you had a lot of visceral fat, or it's more stored in the legs.
And well, it's WAY past the edit window now. The next time you are at 160, I recommend using the tape measure to measure things like waist to chest circumference, and thigh circumference. Then ask if those measurements are bigger than what can be explained by the muscular performance you get. Another thing you can do is try jumping rope, running in place, or doing jumping jacks. When I do these activities, I get "jiggle." My moobs and stomach get jerked around, because there is some flab there. The effect lessens as you lose weight.

What is not objective is looking in the mirror in some lighting and thinking you look pretty good. That's a subjective measurement based on objective reality. Your body might distributed fat in a way that's relatively aesthetically pleasing -- mine does too, it hides it all in the thighs, and people think I'm way more in shape than I am -- and that's not the same thing as being healthy.

Which BMI are you using? The traditional BMI isn't great for very short people - but for the opposite reason you give.

Traditional BMI makes short people think they're thinner than they are.

My argument is that no one can claim BMI or IQ is a scientific form of measurement.
Both are absolutely scientific: they provide good test-retest reliability and correlate with other measures.

Maybe they are crude. Maybe there are better alternatives. That doesn't make them unscientific.

I really don't know how you got here. BMI has been raked over the coals (new and old methods) for being wildly inaccurate for anyone outside of a conditional range. IQ does not predict what to expect from a human being.

Those who double down on IQ as being infallible have something to lose if it's proven to be hack. And history is not on your side here.

> BMI has been raked over the coals (new and old methods) for being wildly inaccurate for anyone outside of a conditional range.

No it hasn't.

BMI doesn't work for three groups of people: it makes very tall or very athletic people think they're fatter than they are, and it makes very short people think they're thinner than they are. But, as GP says, that's less than 5% of the population.

Look at all the effort that's gone into improving hiring. And what're the only factors that people have ever found that actually correlate with job performance? Work sample and IQ.

History is very much on the side of IQ realism. Ten years ago people were denying that a general factor of intelligence existed at all, now it's down to nitpicking or argument from ignorance.

It's perfectly scientific. It just doesn't mean what people think it means.