Too fat? Thank friends and family
STUDY: SOCIAL TIES STRONGLY INFLUENCE HEALTH DECISIONS
By Judy Peres
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 close friend or relative fattens up. 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 public-health 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.
"This is a very common message," she said. "It's all about `what I can do.' It doesn't talk about adopting change in the context of social support. I hope this paper will shift us away from that model, which I don't think has been helpful."
Dr. Richard Suzman of the National Institute on Aging, which funded the study, predicted it would shift scientific thinking about non-communicable diseases and produce a flood of research looking at obesity and other health problems in new ways.
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 to 71 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 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. What you want to do is encourage your friends to change their behavior, too, so you can act in concert with them."
The researchers looked at thousands of people who were followed between 1971 and 2003 as part of the Framingham Heart Study, a long-running research project based in suburban Boston.
The findings are crucial because of the growing health impact of obesity on U.S. residents, Suzman said. With two-thirds of U.S. adults overweight and nearly one-third obese, the epidemic could "neutralize or even reverse . . . the reduction in disability among older people" that has occurred over recent decades, he said.
Christakis noted it could be far more cost-effective to treat a social network for obesity than to treat individuals.
"If we spend $1,000 treating one person who loses 20 pounds," said Christakis, "that would be $50 per pound."
But if the same $1,000 were spent on a strategy that targeted the individual's friends and relatives, he said, the cost per pound lost could be a fraction of that.