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by dtech 2950 days ago
Even for large populations BMI is a pretty mediocre metric since it is heavily influenced by length.

The formula is kept simple `weight / height^2` to help 19th century doctors. A more accurate growth rate for healthy weight is something like `weight / heigth^2.5` [1]

This oversimplification causes standard BMI treshholds to underestimate obesity for short people (<1.6m), and overestimate obesity for tall people (>1.8m).

[1] https://people.maths.ox.ac.uk/trefethen/bmi.html

1 comments

That changed drops my BMI two points, and as a tall person, really seems more in line with where I'm at weight wise. The goal for a normal weight is actually realistic and attainable. I've noticed that tall people only seem to be within the normal BMI range if they are the slender sort - if you look a more normally proportioned tall person you're automatically overweight, and very little extra weight put you in the obese category.
Interesting, for a 2.0m tall person, for a BMI of 22 (normal) you should weight 95kg instead of 88kg for the regular BMI
You can weight 108 kg (238 lbs) instead of 100 (220 lbs) for a BMI of 25 (top of the normal range). 18 lbs is quite a lot of difference, even at that weight. I stand at 198 cm's and hit 238 lbs last summer. At that point I had very little belly fat - 220 lbs would probably get me close to visible abs (the top few at least), which I don't think should be the top of the "normal" category.