Doctor Calls Bullshit On The BMI

Three years after noted “Fat-O-Sphere” writer Kate Harding posted a slideshow illustrating how ridiculous the BMI standards are, the NY Times agrees: the body mass index is unreliable.

In our society, we’re so quick to call someone who appears to be fat “unhealthy.” But health is not a quality that can be judged or seen with the naked eye. There are thin people who smoke and don’t eat any vegetables. There are obese people — including Steven N. Blair, one of the nation’s leading experts on the health benefits of exercise — who jog every day. You can’t see genetic material, a decaying liver or gingivitis in a photograph.

The BMI — which is calculated by dividing your weight in kilograms by the square of your height in meters, doesn’t differentiate between fat and muscle. Dr. Carl Lavie, a cardiologist at the Ochsner Heart and Vascular Institute in New Orleans, tells the Times that according to the BMI: “a six-foot, 250-pound man will be obese.” But! “If he were an N.F.L. lineman of 6-foot-3 weighing 280 pounds, he might be solid muscle with only 2 percent body fat.”

Basically, trying to judge the health of an individual using the BMI? It’s bullshit. To make matters worse, there’s what Dr. Lavie and colleagues have called “the obesity paradox.”

The paradox refers to the repeated finding that while overweight people are more prone to heart failure, patients with heart failure have lower mortality rates if they are obese. The reason for this paradox is far from clear, though Dr. Lavie suggested that one explanation could be that once people become ill, having more bodily “reserve” could be to their advantage.

In many cases, fat has benefits. But the chance that this science will stop folks from calling overweight people unhealthy? Slim.

Weight Index Doesn’t Tell the Whole Truth [NY Times]
Related: BMI Project [Shapely Prose]