Obesity Is Contagious, Study Finds [news]

Wondering why your waistline is expanding? Have a look at those of your friends. Your close friends can influence your weight even more than genes or your family members, according to new research appearing in the July 26 issue of The New England Journal of Medicine. The study's authors suggest that obesity isn't just spreading; rather, it may be contagious between people, like a common cold.

It's not just that people who share similar lifestyles become friends, Fowler says. He and co-author Nicholas Christakis of Harvard Medical School considered the possibility — and were surprised. For one thing, geographic distance between friends in the study seemed to have no impact: friends who lived a 5-hour drive apart and saw each other infrequently were just as influenced by each other's weight gains as those who lived close enough to share weekly take-out meals or pick-up basketball games.