By IANS
New York : You are more likely to be overweight if your friends are, and it doesn't matter if they stay near or far, say researchers.
A new study states that obesity spreads as a kind of social contagion. It has found that having an obese friend makes a person 57 percent more likely to develop a bulging waistline too.
The effect was strongest for close friends but also occurred if friends of friends or even their friends gained weight, reported online edition of health magazine Scientific American.
James Fowler and other scientists at the University of California, San Diego, analysed 32 years of records from 12,067 participants in the Framingham Heart Study, which has followed the health of residents of the small Massachusetts town and their offspring every four years since 1948.
Aside from listing their spouses and family members at each follow up, participants gave names of close friends who would likely know their whereabouts; more than 70 percent of these were also included in the study, creating a dense social network suitable for identifying epidemic-like effects.
The researchers found clusters of obese friends in the network, but the links did not seem to result from people of similar weight flocking to each other or from undetected causes, they report in the New England Journal of Medicine online.
When two people each listed the other as a friend and one packed on the pounds, the other's risk of obesity increased greatly.
However, if only one member of the pair considered the other a friend, obesity was more likely to spread only to the one calling the other a friend.
A person whose friends had obese friends carried an added 20 percent risk of obesity, which fell to 10 percent for friends of the third degree. In comparison, a chunky sibling increased the risk by 40 percent and a spouse by 37 percent.
Geographical location had no bearing on the results: A portly neighbour had no effect, but a friend who gained weight and lived far away still appeared to raise the risk of obesity. People of the same sex also had a stronger impact on one another.
A researcher says the finding fits with other studies that have shown the success of group-based weight loss programmes such as running clubs and weight watchers.