Whether realizing it or not, our ideas about eating, exercise and body image are shaped in part by those closest to us. After tracking more than 12,000 people over 32 years, a recent study shows when one person became obese, his siblings’ risk of also becoming obese jumped by 40%, while his spouse’s risk jumped by 37%. More strikingly, if that person had been named as a “friend” by another participant, the second participant’s risk of becoming obese shot up by 57%. If the friends were of the same gender, the risk was even higher, at 71%. (The study found a man’s weight gain would have no significant effect on his female friend’s weight, and vice versa, but the study did not have many male-female friendships to examine.) If the friends were particularly close - judged in the study by the fact that they both named each other on their lists of loved ones - the risk that one’s weight would follow the others’ increased by a whopping 171%.