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Arthur T Knackerbracket has found the following story:
Cedars-Sinai investigators have developed a simpler and more accurate method of estimating body fat than the widely used body mass index, or BMI, with the goal of better understanding obesity.
The new method is highlighted in a study published in Scientific Reports, one of the Nature journals.
"We wanted to identify a more reliable, simple and inexpensive method to assess body fat percentage without using sophisticated equipment," said the study leader, Orison Woolcott, MD, of Cedars-Sinai.
While the BMI is commonly accepted, many medical experts in the field of obesity consider it to be inaccurate because it cannot distinguish among bone mass, muscle mass and excess fat. BMI also does not account for the influence of gender -- women generally have more body fat than men.
[...] To determine relative fat mass (RFM), you need to measure your height as well as your waist circumference. To measure your waist, place the tape measure right at the top of the hip bone and reach it around your body for the most reliable result. Next, put those numbers into the relative fat mass equation -- making a ratio out of the height and waist measurements. The formula is adjusted for gender:
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(Score: 2) by AthanasiusKircher on Tuesday August 28 2018, @10:31PM
Well, there's a super-obvious reason in that BMI scales with the square of a body measurement (relative to weight) while actual bodies are 3-D and thus BMI only is going to gain in two dimensions while your body gains in three.
The ONLY reason BMI even seemed to work at all was because it was originally intended as a population metric, i.e. something to compare across large numbers of people. It was never intended to be used as a measure for individuals, and doing so was always idiotic.
The only reason it worked in the first place for a population metric is because it is deliberately DESIGNED to scale badly. Why? Because populations have men and women. Women tend to have higher bodyfat percentages (when healthy) than men. Women are also shorter. So you want a metric that allows shorter people to be "fatter" (but still healthy, i.e. women) and taller people to be thinner in bodyfat (i.e. men).
For short men or tall women, BMI is a disaster, as it is for any outliers, like you. But the only people who should be surprised are those who don't understand basic dimensional analysis and don't know why BMI was designed in the first place.
(By the way, you might think you'd get better results by tweaking the exponent in BMI to make it cubed instead of squared. But human bodies don't quite expand equally in all dimensions as they grow taller, so it seems the best exponent is probably in the middle between 2 and 3. But that's still a bad metric given diversity of body shapes, frame size, etc. Again likely the only reason BMI was ever used was because back in the days before calculators, calculating an exponent of 2 was easier than doing 2.4 or whatever. Ironically, old fitness tables used to take into account things like "frame size" when looking at someone -- it's only in the past few decades since we've had access to pocket calculators that doctors decided to advocate for a stupid oversimplified measure that was never intended to be applied to individuals.)