The US is in the midst of an obesity epidemic. Americans just keep getting fatter and fatter. But the bad news doesn’t end there. Because in today’s issue of the New England Journal of Medicine, scientists from Harvard and the University of California in San Diego report that obesity is actually contagious. And it seems you catch it from your friends. After analyzing 32 years worth of data from more than 12,000 individuals, the researchers found that thin people tend to cluster with thin people…and not just for warmth. And that people with more mass tend to gravitate toward one another, too. But it’s not that folks seek friends with a similar physique. Or that people who pack on the pounds all frequent the same fast-food franchises or avoid the same gyms. What the scientists think is happening is that as those around you start plumping out, you come to think that being a bit hefty isn’t such a bad thing. Then as you become larger, so do your friends. And your friends’ friends. And their friends as well. The good news is that losing weight should also make your friends lighter.