Much like a virus, obesity can spread from person to person, according to a new study published this week in the New England Journal of Medicine. When one person gained weight, their close friends tended to gain weight also. Having a friend who was obese would increase your likelihood of becoming obese by 57 %. Having a neighbor who gained weight had no effect and having a family member who gained weight had less of an effect than a friend who gained weight.
--from Study: Obese Friends Could Make You Fat