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Is obesity socially contagious?

This is Science Today. A novel study has found that obesity is ‘socially contagious'. James Fowler, an associate professor of political science at the University of California, San Diego is an expert in social networks and worked with Harvard Medical School on this research.

Fowler: In the statistical analysis, what we found was that if someone that you name as a friend becomes obese, it increases your likelihood of becoming obese in the next two to four years by 57 percent. This is extraordinary! But then the other thing that we found was that when two people name one another as friends, if one of them becomes obese, it increases the risk to the other one by over a hundred percent.

Narrator: And it's not because friends tend to do the same things, like eat or exercise, together.

Fowler: We found that your friend who's five hundred miles away has just as much impact on your obesity as your neighbor next door and so what that suggests is this is about our ideas - if it's the case that we see a lot of people around us getting heavier and we esteem them, they're our friends, then that probably changes our own perception about what an acceptable weight is.

Narrator: For Science Today, I'm Larissa Branin.