Researchers find obesity can spread in social circles

Watch out if your best friend gets pudgy. A new study suggests obesity can spread like an infectious disease and that your odds of becoming obese are much greater if your friends and family put on weight. By studying a social network of 12,067 people who have been closely tracked for the past three decades, researchers found that when one person became fat, those close to them gained as well. The strongest influence was seen among friends no matter where they lived. A person's chances of becoming obese went up 57 percent if a friend became obese. In the closest friendships, the risk almost tripled. Among siblings, the risk of obesity increased by 40 percent and 37 percent among spouses.

"We were stunned to find that friends who are hundreds of miles away have just as much impact on a person's weight status as friends who are right next door," said co-author James Fowler of the University of California, San Diego.

The researchers think it's more than just people with similar eating and exercise habits hanging out together. Instead, it may be that having relatives and friends who become obese changes one's idea of what is an acceptable weight.