Obesity can spread from one person to another like the flu or a fad, researchers reported today in a first-of-its-kind study that helps explain—and could help fight—one of the nation's biggest public health problems.
The study, involving more than 12,000 people tracked over 32 years, found that "social networks" play a surprisingly powerful role in determining an individual's chances of gaining weight, transmitting an increased risk of becoming obese from wives to husbands, from brothers to brothers and from friends to friends.
The risk rose even more sharply among friends—between 57 and 171 percent, depending on whether they considered each other mutual friends. Moreover, friends affected friends' risk even when they lived far apart, and the influence cascaded through three degrees of separation before petering out, the researchers found.
"What spreads is an idea. As people around you gain weight, your attitudes about what constitutes an acceptable body size changes, and you might follow suit and emulate that body size," [Nicholas A. Christakis of Harvard Medical School, who led the study] said. [emphasis added]
"Why Marjorie, what lovely cankles you have! Pass the lasagna, would ya please?"