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Is Obesity Contagious?

That's what the New York Times Magazine is asking on their front cover. But is it true?

Well, two distinguished researchers spent five years looking at the 5,000 plus participants of the Framingham Heart Study (begun in 1948 and continued for two generations) to see what the effects of the relationships among the participants was. Here's their discovery:

Obesity spreads more by association than genes.
"In 1948 fewer than 10% of Framingham residents were obese. By 1985, 18% were, and today about 40% are. What changed? Social norms of diet and physical appearance." Wired, Oct 2009
By studying the Framingham folks as an interconnected network rather than a mass of individuals, the two researchers made this intriguing discovery:
Obesity spread like a virus. Weight gain had a stunning infection rate. If one person become obese, the likelihood that his friend would follow suit increased by 171 percent.
And, your friends are more predictive of your size than your spouse:
"Having an obese spouse raised the risk of becoming obese by 37 percent. If a friend became obese, the risk skyrocketed by 171 percent."
So what do you think? Could this be a contributing factor for the recent increase in obesity?