14 DAY TRIAL // Junk food is considered to be the cause for the fat epidemics: in just 25 years, the number of obese people boomed in the US from 15 % to 33 %. But nobody sticks fatty food in your mouth. At least not directly. However, mentally this happens quite often. And the main culprits are your obese friends.
They can make you believe that the norm is being big, and this way you could be by 50 % more likely to get obese, just like they are. A new research shows that obesity is "socially contagious". Thinness too can be. "Social effects, I think, are much stronger than people before realized. There's been an intensive effort to find genes that are responsible for obesity and physical processes that are responsible for obesity, and what our paper suggests is that you really should spend time looking at the social side of life as well." said co-author James Fowler, a social-networks expert at the University of California-San Diego.
"The suggestion in their paper is that obesity sort of spreads through the network as if it were some kind of epidemic, some kind of contagious disease," said Duncan Watts, who studies social networks at Columbia University.
Previous researches have shown smoke and drink to be socially contagious, too.
Fowler and Nicholas Christakis of Harvard Medical School analyzed health information gathered between 1971 and 2003 from over 12,000 adults involved in the Framingham Heart Study, an ongoing cardiovascular study. Volunteers offered contact information for close friends, many of whom were also study subjects, getting a total of 38,611 social and family ties. The results revealed that of a subject's friends turned obese over the course of the investigation, he was 57 % more likely to turn obese. In case of mutual friends (when both individuals regard the other as a "friend"), the chances were three times higher.
Obese-turned siblings increased the likelihood of their sister or brother turning obese by 40 %, while in case of spouses, the rise was of 37 %. The "obesity contagion" also varied amongst sexes: in same-sex friendships, an obese fried rose by 71 % the vulnerability to obesity. An obese brother made a guy obese with a 44 % increased likelihood, while amongst sisters, the value was 67 %.
The new study focused on mindsets and attitudes as the controlling factors. "It's not that obese or non-obese people simply find other similar people to hang out with. Rather, there is a direct, causal relationship", Christakis said.
The researchers looked at environmental factors that could have affected the obesity levels: in this case, it shouldn't matter if individuals are mutual friends or just one individual names the other as a friend.
But if participants labeled an obese person as a friend, they appeared to be affected by that friend's obesity. But if the person did not label the first person as a friend, the "obesity contagion" was not present. "The fact that it only has an effect when I think you're my friend is very strongly suggestive to me. That's about as good as you can do in terms of identifying a causal relationship", said Watts.
Friends can hang out a lot together and eat similar foods, engaging in the same physical activities, but the research revealed that the geographic proximity of friends did not matter. "So friends that are thousands of miles away have just as large an impact on you as friends who are right next door," Fowler told LiveScience.
"What appears to be happening is that a person becoming obese most likely causes a change of norms about what counts as an appropriate body size. People come to think that it is OK to be bigger since those around them are bigger, and this sensibility spreads," said Christakis.