"The way to avoid becoming fat is to avoid having fat friends"

New Study showing that Obesity may be a social thing shared among friends.

Obesity can spread from person to person, much like a virus, researchers are reporting today. When one person gains weight, close friends tend to gain weight, too.

Their study, published in The New England Journal of Medicine, involved a detailed analysis of a large social network of 12,067 people who had been closely followed for 32 years, from 1971 to 2003.

The investigators knew who was friends with whom as well as who was a spouse or sibling or neighbor, and they knew how much each person weighed at various times over three decades. That let them reconstruct what happened over the years as individuals became obese. Did their friends also become obese? Did family members? Or neighbors?

The answer, the researchers report, was that people were most likely to become obese when a friend became obese. That increased a person’s chances of becoming obese by 57 percent. There was no effect when a neighbor gained or lost weight, however, and family members had less influence than friends.

It did not even matter if the friend was hundreds of miles away, the influence remained. And the greatest influence of all was between close mutual friends. There, if one became obese, the other had a 171 percent increased chance of becoming obese, too.