Last week the terrific health writer Jane Brody used her weekly column in the New York Times (April 15, Science Times) to criticize overreliance on Body Mass Index (BMI) as an indication of people being overweight or obese. If anything, she was too mild in her criticism of a standard that has been used to hound fat people about their weight rather than them, and all of us, being urged to be as healthy as possible. ("Fat" rather than "obese" is the preferred term by many in the overweight community. I use both).
BMI is a ratio of weight to height (weight in kilograms divided by the square of the height in meters). The BMI was devised in the nineteenth century as a statistical tool and meant to be a way to assess weight in the population generally. However, over time, it became an easy and inexpensive way to target individuals as being too large: greater than 25 considered as overweight; over 30 considered obese; over 40 morbidly so. BMI seems to be a straightforward way to determine if an individual has excessive weight (and how much) and to track the number of those with such issues in the general population and various subgroups.
But there are lots of criticisms of this measure.