NYTimes: 'Study Says Obesity Can Be Contagious', 7/25/07

by Gina Kolata
http://www.nytimes.com/2007/07/25/health/25cnd-fat.html?hp=&adxnnl=1&adxnnlx=1185393658-dKjEuH1JGMxvxifjLHZ09Q

* A detailed analysis of a large social network of 12,067 people who had been closely followed for 32 years, from 1971 until 2003 was recently published in the New England Journal of Medicine. It suggests "obesity can spread from person to person, much like a virus, researchers are reporting today. When one person gained weight, their close friends tended to gain weight, too."

* "There was no effect when a neighbor gained or lost weight, however, and family members had less influence than friends."

* "Dr. Nicholas Christakis, a physician and professor of medical sociology at Harvard Medical School and a principal investigator in the new study, says one explanation is that friends affect each others' perception of fatness. When a close friend becomes obese, obesity may not look so bad."

* Of course, the investigators say, social networks are not the only factors that affect body weight. There is a strong genetic component at work as well."