You, Your Friends, Your Friends of Friends

But what seems obvious in the abstract can lead to surprising findings. A recent study found that obesity can spread from friend to friend much like a virus. When one person gains weight, close friends tend to gain weight, too.
The study, published recently in The New England Journal of Medicine, involved a detailed analysis of a large social network of 12,067 people who had been closely followed for 32 years, from 1971 to 2003.
Now, scientists believe that social networks not only can spread diseases, like the common cold, but also may influence many types of behavior — negative and positive — which then affect an individual’s health, as well as a community’s.