Friendship may be tribal, but it works the other way around, too. The bodies of our friends can affect our own physical appearance. A nearly ten-year-old study in the New England Journal of Medicine found that “obesity can spread from person to person, much like a virus . . . When one person gains weight, close friends tend to gain weight too.”1 Explains Harvard professor Nicholas Christakis, a principal investigator in the new study, “One explanation is that friends affect each others’ perception of fatness. When a close friend becomes obese, obesity may not look so bad.”
