“You Want Another Slice of Pizza?”

OBESITY and SOCIAL NETWORKS

The people around us influence our interests, our beliefs, our taste in music…and our waistlines. That’s right, our waistlines. Humans are social creatures. We eat together. We play sports on teams. We watch TV together. We do almost everything with other people. So it should come as no surprise that when a close friend stops exercising, starts eating less healthy foods, and ultimately gains weight, your chances of gaining weight increase significantly.


The Harvard Medical School released a study in July 2007 documenting this phenomenon. The 32-year study of 12,067 people found that if a person’s close friend becomes obese, that person’s chance of becoming obese increases by 57%; for siblings the increase is 40%; and for spouses the increase is 37%. The study also found that two close friends or sibling living far apart, still influence each other’s weight. Nicholas Christakis, MD, PhD, a professor in Harvard Medical School’s Department of Health Care Policy suggests that this influence across great distances may be caused by “a change of norms about what counts as an appropriate body size. People come to think that it is okay to be bigger since those around them are bigger, and this sensibility spreads.”

The good news is that our social networks can also work in the opposite direction, having positive influences on our health.

Christakis highlights the following three points from this study:
-Obesity is not just an individual phenomenon, but also a collective social phenomenon.
-Interventions should target groups of people rather than individuals. People loosing weight together is likely to be more effective than people loosing weight on their own.
-Prevention or treatment of weight gain in one individual will likely have ripple effects through social networks impacting others.

These findings underscore the importance of community-wide health interventions with components that influence social networks. Healthy and Active Communities include strong social networks of support, such as walking clubs, youth sports teams, and farmers’ markets.

“You want to go for a walk?”

Key elements of lasting change: Policy Change, Environment Change, and Social Change.

The full study can be found in the New England Journal of Medicine, July 26, Vol. 357, No. 4