Can Facebook Make You Fat?

If absence makes the heart grow fonder, proximity can make the whole body fatter.

The Harvard Medical School suggests obesity is a virus transmitted by friends and family. A study of more than 12,000 people over 32 years finds social networks are crucial to putting on weight.

The influence apparently goes well beyond getting together and ordering pizza. According to the researchers, when one spouse gets fat, the other is 37 percent more likely to, compared with other couples. Brothers of obese men have a 40 percent higher chance of blimping up, too.

The risk is even greater among friends, between 57 and 171 percent, even when they live far apart, leading to the conclusion that “new social norms can proliferate quickly.”

Nicholas A. Christakis of Harvard Medical School, who led the study, to be published in the New England Journal of Medicine, concluded, “We are finding evidence for a kind of social contagion."

So the answer to keeping weight down is obvious: Stay away from sumo wrestlers, and hang out with fashion models.