Time to replace the BMI as a measure, or otherwise, of obesity

20 January 2025

The Body Mass Index (BMI), may, at last, be about to be shown the door. Health care experts from across the world have been calling for a new means of defining obesity, according to research published by The Lancet:

We recommend that BMI should be used only as a surrogate measure of health risk at a population level, for epidemiological studies, or for screening purposes, rather than as an individual measure of health. Excess adiposity should be confirmed by either direct measurement of body fat, where available, or at least one anthropometric criterion (eg, waist circumference, waist-to-hip ratio, or waist-to-height ratio) in addition to BMI, using validated methods and cutoff points appropriate to age, gender, and ethnicity.

It’s always struck me as an odd way to determine whether a person is of a healthy, or otherwise, weight, simply by dividing their height by their weight.

My BMI has always been in the OK zone, but I often wondered how it could useful for people who are, say, professional athletes, or front-rowers of the Wallabies. Surely their height to weight ratios would send the BMI into meltdown. I queried a past GP about this, who told me the BMI was but one tool available to medical professionals, but did not elaborate further.

I made me immediately think if there are other such measures, why aren’t they used more widely.