Thin Friends Can Make You Fat, Too

This summer, we learned some enlightening and also depressing news about weight gain. An article [2] published in the New England Journal of Medicine claimed that fat friends can make you fat, even if you live thousands of miles away from them. Now comes another study [3] that adds another confusing caveat to the whole subject. If you hang around thin people who overeat, you’re likely to copy them, too, concludes a recent article published in the Journal of Consumer Research [4]. For those of us trying to watch our weight, who can we break bread with?

The first study about overweight friends got so much attention that it was seen as an important example of the emerging science of social contagion [5] in which people “infect” one another with their good or bad behavior, in the same way a virus spreads. It is a commentary on friendship as much as weight gain; we mimic the people we know and love. But the second study suggests another powerful factor that doesn’t include that same footnote on friendship and love. Subjects in the study tended to mimic whatever the size zero woman in their midst was doing. The point is that we care so deeply about body image that we lose sight of our own cravings and appetite signals. The even more unsavory message is the strong prejudice young women have against their overweight peers.

In the “fat friends” study, researchers looked at the social ties among the 12,000 participants of the Framingham Heart Study [6] over three decades, and found that a person’s chances of becoming fat increased 57 percent if they had a friend who had gained a significant amount of weight during a given period. How that happens isn’t clear. Do fat friends share more unhealthy food? Give each other permission to make another round at the buffet?

However, the “thin peers” study suggests that others influence what we eat based on how they look. Researchers at the University of British Columbia [7] wanted to observe whether women would adjust their snacking behavior depending on whether the person next to them was thin or obese. In a series of experiments, 210 college undergraduate women who mostly had a normal body-mass index were told they would be participating in a study about movie-watching. During the fake screening, they were paired with a hired actress posing as a fellow student, and offered granola or candy. The actress, who was 5 feet 2 inches tall, weighed 105 pounds, and wore a size zero, always helped herself first. When she took a large portion, the majority of students copied her, regardless of whether she took the healthy or unhealthy food. But when the actress wore a fat suit, which made her look as if she weighed 180 pounds and wore a size 16, the students generally consumed a much smaller amount.

The conclusion: Women look to one another for social cues about eating, yet they take into account body size, adopting the behavior of the person whose physique they admire and distancing themselves from the behavior of the person they don’t. “They think, If the [thin person] eats it, so can I,” says assistant marketing professor and lead author Brent McFerran. “But if the person is heavy, they think, I better not eat so much.” Therefore, a person is more at risk of eating too much when she is around a thin person with a big appetite.

The thin peers study offers interesting insight into how others’ body size might affect our own eating decisions—and if we’re blindly copying the thin person—how much we’re in denial about our own hunger and metabolism. But the study faces obvious limitations. First, the students were strangers who were observed in a controlled artificial setting, whereas the subjects in the Framingham study were longtime friends who were tracked in the real world. Second, in an attempt to focus the study on women, who are more sensitive to body comparisons than men, the researchers exclusively recruited young college women. Although undergraduate students often serve as excellent warm bodies for all kinds of campus experiments (they were compensated $10 each), many at that age are painfully coming to terms with their body shape and size.

These women are definitely not representative of the rest of the female population, and it’s hard to make sweeping social statements based on their behavior. Undergraduate women experience a higher risk of disordered eating and body dissatisfaction than any other segment of society, says Marlene Schwartz, deputy director of the Rudd Center for Food Policy and Obesity at Yale University [8]. Younger women in general are also more likely to have a negative attitude about obese people than men or older people. Her 2003 study of anti-fat bias in health professionals [9] specializing in obesity found that younger women were the most prone to associate being fat with being lazy or stupid. Since young women often assign meaning to how much they eat, they tend to believe food consumption is a measure of their self-worth, says Schwartz. If they’re insecure about their own bodies and want to feel superior to overweight people, they think that their choice to take less food shows how much self-control they have. “[The study subjects] responded to whatever fear and anxiety was triggered by being around the obese person by saying, ‘I’m not like that,’ ” Schwartz said.

The desire to identify with the thin person was so strong that students ate large portions, even if that very behavior put them at risk of gaining weight. In another experiment that used just candy, they also ate less when she took a smaller portion, perhaps concluding that they needed to match her habits to be slim, says McFerran. When the actress dressed in the fat suit ate smaller amounts, the subjects actually ate more that she did, perhaps trying to distinguish themselves by showing they didn’t need to be on a diet.

The good news is that McFerran’s research also shows that women with higher self-esteem are less hung up on linking their food choices to what others around them weigh. The same is true of older women, who thankfully become more comfortable in their own skin as they age. However, some women of all ages never outgrow the complicated set of rules about how they eat in front of one another, says Schwartz. Since food is an important way of connecting, the need to set oneself apart eventually gives way to the bigger desire to belong to the group. If one woman in a group orders dessert, others feel compelled to follow suit or at least ask for extra forks to share so they don’t appear “holier than thou,” she says. However, if she swears off dessert, the other women at the table are more likely to do so, proudly saying, “None for me, either.”

A better response would be for each of us to take responsibility for what we eat and make decisions based on our own wills, metabolisms, and exercise schedules. But inevitably, we will be swayed by what others are doing. In those cases, we can improve our chances of picking up healthy habits by socializing with good role models, no matter how much they weigh.

Photograph of a slice of cake on the homepage by Stockbyte/Getty.