Friendship can raise heavy issue

The Baltimore Sun

Forget the common cold - it's fat you might catch from your best friend.

A new study finds that obesity "spreads" through social networks. And, incidentally, so does skinniness.

"We are not suggesting people break ties with overweight friends, but making friends or forming ties with people who are the proper weight is likely to be beneficial," said Nicholas Christakis, the Harvard sociologist who led the study.

The study, which was published in today's New England Journal of Medicine, indicated that a person's chances of becoming obese increase by 57 percent if someone he identifies as a friend becomes obese.

People who identified each other as close friends were found to have almost triple that risk. When one becomes obese, the other has a 171 percent greater chance of following suit, the study found.

Relatives are similarly affected. The study found that the chance of becoming obese rose 40 percent if a sibling became obese and 37 percent if a spouse became obese.

The findings didn't surprise Brooke Hollingsworth, 22, a fit workout enthusiast who was eating lunch at the Inner Harbor in Baltimore yesterday.

"I don't have any friends that are obese - maybe a couple guy friends that are overweight - but less than a handful as far as girls," she said. "If you have friends that eat badly, you probably will too."

The researchers used data from the Framingham Heart Study, which has closely followed more than 12,000 people in three generations over 32 years.

The subjects were residents of Framingham, Mass., a predominantly white, middle-class city of 65,000.

Because few participants dropped out of the study and information about friends and relatives of the participants was readily available, Christakis and co-author James Fowler, a political scientist at the University of California, San Diego, were able to re-create the participants' social networks.

They found groups of closely tied people who were obese and groups of closely tied thin people. That indicated a "transmission of obesity from one person to another," Fowler said.

With more than 66 percent of American adults and nearly 20 percent of children ages 6 to 10 classified as overweight or obese, the study sheds light on a critical issue, experts said.

"What was thought to be noninfectious is clearly communicable," said Dr. Richard Suzman, a director of behavioral research at the National Institutes of Health who was not directly involved in the study.

Further research might help identify why certain parts of the country and world have higher obesity rates than others, he said.

"It's really very interesting," said Nancy Olins, communications director for the the Obesity Society, a research group based in Silver Spring. "If one person is obese, they can influence other people. This is something new that we haven't explored before."

The researchers also found that same-sex friendships are more influential than those between men and women. Although spouses are intimate, Fowler said, "men will look to men, women look to women."

Katie Duffy, 21, a waitress at the Big Kahuna Cantina on Light Street, said that makes sense.

"You're always comparing yourself to the same gender," she said. "My best friend is small, real, real small, and I never want to eat much when I'm around her."

Researchers found that the social aspect of obesity has little to do with who the exercise or dining partners are.

"Your friend that's 500 miles away has just as much effect on your obesity as your neighbors next door," Fowler said. "This is about our ideas and about what level of weight is healthy."

Everyone has an impression of what his or her "ideal weight" should be, an impression largely shaped by the way other people look, said Dr. Soren Snitker, an obesity researcher at the University of Maryland School of Medicine. "Even though we see all these thin models on TV, over the years this ideal has shifted to a higher weight."

Some experts argue that obesity is about genetics and that some people are predisposed to gaining weight. Snitker, however, argues that "you wouldn't have obesity without environment, but you also couldn't have obesity without genetics."

The increase in Americans' weight over the past three decades has nothing to do with genetics and everything to do with environment, Snitker said.

"Environment could include the people around us - those we esteem - but it could also involve national policy and public transportation access," he said.

At Harvard, Christakis has spent his career studying the ways that acquaintances affect people's health. In a previous project, he explored the ways poor health in one spouse can severely affect the health of the other. He has also studied the ways drinking and smoking habits spread through social networks.

Using complex mathematical models to study such relationships can improve public health, Christakis said.

"It may mean that treating people in groups might be more effective," he said. "If we spend $1,000 to prevent obesity in one person and they lose 20 pounds, that's $50 per pound, but if it inspires a cascade of weight loss in others, that could be 200 pounds."

Baltimore dietitian Sara Foote said that having healthy friends means nothing if someone is not self-motivated.

"I've seen people who come to the gym and make friends with people who are healthier," said Foote, director of weight management and nutritional services at Merritt Athletic Clubs. "But the point is, they are not coming into the gym until they are ready to make changes."

Foote said support networks are important.

"I see a lot of middle-aged women, and if their husbands won't join them, I tell them to find a girlfriend they can exercise with," she said.

sindya.bhanoo@baltsun.com

By the numbers

If someone close to you becomes obese, chances are that you will, too. The risk goes up:

57

percent if the person is a friend

40

percent if the person is a sibling

37

percent if the person is your spouse

Study information:

Participants in the study, 12,067; length of the study, 32 years.

[Source: Harvard University and the University of California, San Diego]

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