Friendship Fatness Factor

I read some interesting articles in today’s Wall Street Journal, New York Times and Los Angeles Times which suggests that your friends can make you fat. How is that? According to a study in this week’s New England Journal of Medicine, social networks have a greater effect on your chances of becoming obese than your genes. These findings could help explain why obesity is rising in America despite widespread dieting and other weight-loss techniques. The findings also suggest that public health initiatives to fight obesity should take social networks into account, and work with overweight people in groups, as Weight Watchers International has done for years.

Dr. Nicolas Christakis of Harvard Medical School said the results indicate that behavioral “norms” shift depending on how people in a social circle look and act, even if they only meet once a year. “People might say, ‘Look, Christakis is getting fat. It’s okay for me to be obese as well. You change your idea of what is an acceptable body type by looking at the people around you.” Surprisingly, social contacts propelled weight gains even among individuals a thousand miles apart, indicating that social proximity overrides geographic proximity.

“It’s become very fashionable to speak of an obesity epidemic,” says Dr. Christakis. “But we wondered, in fact, is obesity really an epidemic, with person to person transmission? Was there a kind of social contagion?”

The study found there was. A person’s chance of becoming obese jumped 57% if s/he also had a friend who became obese. Among siblings, the risk goes up 40%. Between spouses, the odds rise 37%. Mutual friends had the greatest influence. If one became obese, the risk skyrocketed 171%. The phenomenon worked in the opposite direction as well. People who became thinner, increase the chances that their friends and relatives will lose weight too.

The study examined 12,067 people who had been closely followed for 32 years from 1971 to 2003. Over the years, each participant was asked to list close friends and workplace contacts to allow doctors to track them down. From these contacts, researchers examined 38,611 family and social relationships, charting associations between a person’s weight gain and the weight gain among his social circle.

The study is part of a larger trend in science and social science to examine the effect of networks, from the role that interconnected neurons play in cognition, to even networks of terrorism. “Networks are really important for the transmission of ideas and values,” says Katherine Stovel, a University of Washington sociology professor who studies networks. “People come to resemble each other.” But, she cautioned, “I don’t want anybody to read this and think about dropping friends because they’re fat.”

Wow, the findings of this study really blew me away because practically all my friends have gained weight over the past ten years or so (and I have too, unfortunately). It’s definitely hard to lose weight when you witness all your friends gaining weight. I think where you live can also influence whether or not you gain or lose weight. When I lived in Hawaii from 2000 - 2003, I was able to maintain my weight at 110 pounds and I could wear a size 0, but all that changed when I moved back to California. Now, I weigh 115 pounds and I wear a size 2 or 4.

Sources: The Wall Street Journal, New York Times, Los Angeles Times