In medical and public health discussions, weight status is frequently discussed in terms of BMI, or body mass index. Developed in 1832 by Belgian mathematician, statistician, and astronomer Adolphe Quetelet, the “Quetelet Index” is calculated by dividing an individual’s weight in kilograms by the square of their height in meters. Quetelet was not concerned with matters of obesity and/or health when he developed his calculation; his goal was to delineate the physical attributes of the “normal” (average) man. In 1972, physiologist and researcher Ancel Keys adopted the Quetelet Index (renaming it the Body Mass Index), noting that the BMI formula “proves to be, if not fully satisfactory, at least as good as any other relative weight index as an indicator of relative obesity” (Keys, et al., 1972).
But just how useful is BMI as a measure of health?
From FiveThirtyEight: BMI is a terrible measure of health
From the article:
"A study by researchers at UCLA published this month in the International Journal of Obesity looked at 40,420 adults in the most recent U.S. National Health and Nutrition Examination Survey and assessed their health as measured by six accepted metrics, including blood pressure, cholesterol and C-reactive protein (a gauge of inflammation). It found that 47 percent of people classified as overweight by BMI and 29 percent of those who qualified as obese were healthy as measured by at least five of those other metrics. Meanwhile, 31 percent of normal-weight people were unhealthy by two or more of the same measures.Using BMI alone as a measure of health would misclassify almost 75 million adults in the U.S., the authors concluded".
From Slate: Why are doctors still measuring obesity with the body mass index?
(provides a useful history on how BMI came to be the standard measure for obesity, and a proxy for health status)
Keys, Ancel, Fidanza, Flaminio, Karvonen, Martti J., Kimura, Noboru, & Taylor, Henry L. (1972). Indices of relative weight and obesity. Journal of Chronic Diseases, 25(6), 329-343.