A life in the day

7/27/2004

BMI

Filed under: — site admin @ 12:28 pm

I don’t understand the justification for the Body Mass Index (BMI). I guess they’ve found a strong correlation between BMI and body fat percentage, and the correlation is the most important thing. But I don’t understand the units. It’s measured in kg/m2. Wouldn’t kg/m3 be more logical? Are we supposed to be two dimensional?

This scale would give the same score to a five-footer and a six-footer who weighs just 44% more (62/52). I would expect that the logical equilibrium point would be 72.8% more (63/53.) I know that children are treated somewhat differently, but in the existing scale, a 25-pound three-foot tall child would scale up to a six-foot tall adult weighing only 100 pounds.

(For those with more logical measurement scales, 2.2 pounds = 1 kilogram, and 1 foot = 12 inches = 30.48 centimeters.)

I can find many BMI calculators online, and some medical references to the relationship between BMI and body fat percent. But nothing explains why the units are in mass/height2.

I’m puzzled.

Update: A more recent entry notes that the use of the BMI by medical professionals is being eliminated.

One Response to “BMI”

  1. A life in the day… » BMI update Says:

    […] 10/5/2004 BMI updateFiled under: Diabetes — Scott Sauyet @ 2:03 pm In a July entry I discussed my confusion about the unit […]

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