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Spokane, Washington  Est. May 19, 1883

Feeling fat? Blame it on your friends

Judy Peres Chicago Tribune

CHICAGO – Your friends may be more important than your genes in determining whether you gain weight, according to a new study billed as the first to demonstrate that obesity tends to spread through social networks.

The study, which followed a large group of Americans for more than three decades, found that a person’s chances of becoming obese increase dramatically after a friend or relative gains weight. The same thing happens when someone close slims down.

The authors of the paper speculate the reason is “the spread of norms from people to people. People change their minds about what constitutes an acceptable body mass index” as their close friends gain or lose weight, said co-author Dr. Nicholas Christakis of Harvard Medical School.

Experts agreed that the research, published in this week’s New England Journal of Medicine, could influence efforts to combat the epidemic of obesity that is threatening many gains made by medical science.

The study discredits the traditional approach to weight management that says, “Buck up, eat less, exercise more – it’s all up to you,” said Dr. Katherine Kaufer Christoffel, director of obesity management and prevention at Children’s Memorial Research Center in Chicago.

Christakis and his co-author, James Fowler, found that people’s chances of becoming obese increase by 57 percent if someone they consider a friend becomes obese. The link is even stronger if the two people each name the other as a friend. If one of the mutual friends becomes obese, the chance for the other to follow suit goes up 171 percent.

An editorial accompanying the study pointed out that the effect of friendship on obesity appears to be even stronger than that of a known hereditary cause, a mutation in the so-called “fat gene.” A single copy of this mutated FTO gene raises risk of obesity by 30 percent. People with two copies are 67 percent more at risk.

The study authors said they were not suggesting people should ditch their overweight friends, though people might want to consider expanding their social network to include more people with a healthy weight.

“There’s a ton of research that suggests having more friends makes you healthier,” said Fowler, of the University of California, San Diego. “The last thing you want to do is get rid of friends.”