Study: Obesity is Socially Contagious

A new study finds that when the scale reads "obese" for one individual, the odds that their friends will become obese increase by more than 50 percent.

The study, published in the July 26 issue of the New England Journal of Medicine, suggests that obesity is "socially contagious," as it can spread among individuals in close social circles. The likely explanation: A person's idea of what is an appropriate body size is affected by the size of his or her friends.

Conversely, the researchers found that thinness is also contagious.

"Social effects, I think, are much stronger than people before realized," said co-author James Fowler, a social-networks expert at the University of California-San Diego. "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."

...Fat-fueling factors were taken into consideration. For instance, the researchers made sure the effect wasn't a case of "birds of a feather flocking together." Body measurements were taken throughout the study period, showing when individuals became obese and whether they began the study with obese readings.

"It's not that obese or non-obese people simply find other similar people to hang out with," Christakis said. "Rather, there is a direct, causal relationship."

They also ruled out the idea that an outside factor, and not the friendship, caused the fatness. If an environmental factor were affecting both individuals in a friendship, then it shouldn't matter whether individuals are mutual friends or just one individual labels the other as a friend.

The study, however, found that it does matter which way the friend arrow points: If subjects named an obese person as a friend, they tended to be affected by that person's obesity.

But when the person on the receiving end did not label the first person as a friend, there was no "obesity contagion" effect in the other direction. The distinct variable here is who calls whom a "friend."

"The fact that it only has an effect when I think you're my friend is very strongly suggestive to me," Watts said. "That's about as good as you can do in terms of identifying a causal relationship."

Perhaps friends just spend a lot of time together and so would eat similar foods and engage in the same physical activities. But they found the results held no matter the geographic proximity of friends.

"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.

The scientists suggest the findings can be explained if friends are influencing one another's norms for body weight.

"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," Christakis said. "People come to think that it is OK to be bigger since those around them are bigger, and this sensibility spreads."
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I've thought that this was probably the case.

In a somewhat related issue is this article about cultural norms favoring obesity in Mauritania ->

In Mauritania, to make a girl big and plump, ‘gavage’ — a borrowed French word from the practice of fattening of geese for foie gras — starts early. Obesity has long been the ideal of beauty, signaling a family’s wealth in a land repeatedly wracked by drought.

Mint was 4 when her family began to force her to drink 14 gallons of camel’s milk a day. When she vomited, she was beaten. If she refused to drink, her fingers were bent back until they touched her hand. Her stomach hurt so much she prayed all the animals in the world would die so that there would be no more milk.

By the time Mint was 10, she could no longer run. Unconcerned, her proud mother delighted in measuring the loops of fat hanging under her daughter’s arms.

“My mother thinks she made me beautiful. But she made me sick,” says Mint, who suffers from weight-related illnesses including diabetes and heart disease. She asked that her full last name not be disclosed because she feels embarrassed.

A quarter of the 1.5 million women in Mauritania — a barren, dune-enveloped country in northwest Africa more than twice the size of Texas — are obese, according to the World Health Organization. That’s lower than the 40 percent of American women who the WHO says are obese, but surprisingly high in a country that has not a single fast-food franchise...

To end the brutal feeding practices, the government has launched a TV and radio campaign highlighting the health risks of obesity. Because most Mauritanian love songs describe the ideal woman as fat, the health ministry commissioned catchy odes to thin women.

These efforts, combined with the rising popularity of foreign soap operas featuring model-thin women, has helped reduce the practice, especially among the country’s urban elite.

Only one in 10 women under the age of 19 has been force-fed, compared to a third of women 40 or older, according to a survey conducted by the National Office of Statistics in 2001, the most recent available.

Those still forced to eat were overwhelmingly from the country’s rural areas.

But although the canon of beauty is changing, entrenched values are hard to uproot.

“My husband thinks I’m not fat enough,” complained Zeinabou Mint Bilkhere, explaining that her husband found her pretty during the last months of her pregnancy. Since giving birth, the weight has dropped, however, and with it his desire for her....

“When I was little, my mother hit me to eat because I didn’t want to be fat. Now I want to be big because men like that,” said Bilkhere, who wants to gain more than 20 pounds.

But many men say they prefer voluptuous women.

Isselmou Ould Mohamed says he loves his wife’s 200-pound body and was pleased when she began adding even more weight during pregnancy. When he learned she had started walking around the soccer stadium to try to shed the extra pounds, he was revolted.

“I don’t like skinny women. I want to be able to grab her love handles,” said the 32-year-old. “I told her that if she loses a lot of weight, I’ll divorce her.”

Although Mauritania is the only culture known to force-feed girls, obesity is popular across much of the Arab world. Nomadic peoples struggling to survive the harsh desert came to prize fatness as a sign of health.

Fifty-two percent of women over 15 in Kuwait are obese, as are 46 percent in Egypt and approximately a third of women in Saudi Arabia and Bahrain, according to the WHO. That contrasts sharply with most sub-Saharan countries, including Mauritania’s neighbors, Senegal and Mali, where only 9 and 6 percent of women are obese...

“A man’s goal is to marry a woman that fills his house. She needs to decorate it like an armoire or a TV set,” said Seif l’Islam, 48, curator of a library of ancient Islamic manuscripts, which include numerous love poems to plump women.
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It's interesting because it shows how a society can affect values. Of course - women and their health seem to be valued very little. Valuing obesity past the point of ill health is just like valuing thinness to the point of anorexia and death.

I was brought up with the value of good health - and I wouldn't tolerate someone who encouraged me to be unhealthy - for his vanity or for any other reason.