No matter what the latest newspaper headlines say, obesity is not a contagious disease although it does seem to spread across a social network according to this large NEJM study based on the Framingham cohort (free full text).
Authors claim that a person's chances of becoming obese increased by 57% if he or she had a friend who became obese in a given interval. In family networks, if one sibling became obese, the chance that the other would become obese increased by 40% and if one spouse became obese, the likelihood that the other spouse would become obese increased by 37%.
The most striking association was observed among adult males: "Among friends of the same sex, a man had a 100% increase in the chance of becoming obese if his male friend became obese, whereas the female-to-female spread of obesity was not significant (38% increased chance)."
See the animation model of obesity spread across a social network over 32 years.
Is it my impression or the NEJM has become just a little bit off the beaten track lately? Have a look at the following topics:
A cat which predicts deaths in a nursing home
Sudden Death from Sand Holes
Bungee jumping and retinal hemorrhage
Social network and obesity
The Spread of Obesity in a Large Social Network over 32 Years. Nicholas A. Christakis, M.D., Ph.D., M.P.H., and James H. Fowler, Ph.D. NEJM, Volume 357:370-379, July 26, 2007.
More than a quarter of Ohio adults obese, new rankings say. Plain Dealer, 08/2007.
Image source: NEJM.