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Is Obesity Contagious?

Dr. Jonathan LaPook is the medical correspondent for the CBS Evening News with Katie Couric.
Tonight's story focuses on a report from the Framingham Heart Study that suggests that obesity – and thinness – can spread through social ties. And it's not just that obese people tend to hang out together. If one of a pair of mutual friends BECOMES obese (defined as Body Mass Index, or BMI>= 30) then the risk of the other becoming obese increases by 171%! And social closeness is much more important than geographic closeness. There was no effect for next door neighbors who weren't friends. But a friend 1,000 miles away influences you as much as a friend next door.

One of the most surprising findings was that the effect extends out three levels of friendship. Not only are you affected by your friend, but by your friend's friend and your friend's friend's friend. If everybody is connected by six degrees of separation, think how many people might be influenced by three degrees of separation!

I spoke to James Fowler, Ph.D., an author of the study appearing in July 26th's edition of the The New England Journal of Medicine. He is excited about the public health implications of this study. Think how many people might be helped by one person's healthy lifestyle. The same effect that can cause an obese friend to increase a friend's risk of obesity by 171% works the other way too. As Dr. Fowler told me, "When your obese friend loses weight and becomes either overweight or a normal weight, it reduces your risk of obesity by 63%."

Harnessing the power of friendships may well be the new new thing in medicine.

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