The XX Factor

Your Little Pot Belly Probably Won’t Kill You

This is a guest post from Slate senior editor Daniel Engber .

There’s a study out today from the New England Journal of Medicine with a conclusion that may not come as a shock: Being overweight, the authors say, can kill you. ” Body-Mass Index and Mortality among 1.46 Million White Adults ” pools the results from 19 studies and corrects the data for smoking status and preexisting disease. Among Caucasian women, being overweight-which means having a BMI between 25 and 29.9-corresponds to a 13-percent increase in risk of early death. (The numbers were similar, but lower, for men.)

Before you start writing your will, let’s give the numbers a closer look. The new study looked at a huge number of people, but it wasn’t exactly representative of the U.S. population. Consider that just 13 percent of the participants were smokers, compared with the national rate of 21 percent . Forty-six percent were college-educated, versus 25 or 30 percent of everyone else. And, of course, 100 percent of the sample was white-as opposed to 66 percent across the country.

Does that make a difference? We know that the health effects of obesity are unequally distributed across ethnic and gender groups. A 2006 study by Peter Muennig found that white women-the people highlighted in the new paper-are precisely the ones most susceptible to weight-associated disease. According to Muennig, a young black woman who’s 5 feet 5 inches won’t develop any weight-related risk of early death until she reaches 225 lbs. Meanwhile, a white woman of the same height and age group would hit the same threshold at 170 lbs.

The NEJM study raises other questions, too. It doesn’t tell us, for example, whether the 13-percent increase in risk is a direct result of being overweight-i.e. whether it’s the pot belly itself that’s killing you, or some other factor that happens to cause both overweight and early death. There are some obvious suspects for this mystery factor: A poor diet and lack of exercise, for example, can make you overweight, while also putting you at greater risk for heart disease, stroke and diabetes. (The new study did make a crude control for levels of physical activity.)  If that’s what drives the data, then our health policy shouldn’t focus on making people thin , so much as making them eat right and go to the gym .

Photograph of a slightly overweight belly by Wikimedia Commons.