current theory is that when someone becomes obese, it makes it more socially acceptable for people close to that person to gain weight. The change in social norm of acceptable body size can spread quickly, rippling through networks like rings spreading from a pebble thrown into a pond, even among people who live hundreds of miles away from one another. The spreading effect is more pronounced in friends of the same gender. Gains in weight appear to spread through a population—with friends and relatives apparently influencing other friends and relatives, for example—in a way reminiscent of a contagious disease.
The point is this: We choose the weight at which we’re comfortable, bearing in mind the weights of our peers. This is because we care about our status and position in society. If we assume that relative slimness confers status, it makes sense that we would choose to weigh a little below the norm in our social networks. But as that norm creeps up, we’re comfortable having our own weight creep up, too—as long as it remains close to the weight of our peers. When my friends get a little fatter, I feel okay about becoming a little fatter myself. As a scientist in this field, I believe that these changing norms have had a profound influence on the rapid spread of obesity.
Eating is a social activity
When it comes to social influences, it’s not just norms that affect us. Who we eat with matters, too. So does the way we were raised. Deanne Hobba’s experience is a good example of this. Deanne had been heavy all of her life. Most of her family members and friends were heavy and inactive. She grew up in a huge Italian family where everything revolved around food, she says: “Every Sunday, we had these giant pasta meals, and the refrain was always ‘eat, eat, eat.’ Every family celebration centered on food. I grew up thinking that’s the way it should be, and it was very hard to break out of this mindset.”
Eating is a highly social activity, and perhaps not surprisingly, we model our habits on those of the people around us, especially family. What your parents ate while you were watching them across the table affects what you eat now. (However, contrary to popular belief, their admonitions to eat your fruits and vegetables did not result in greater consumption of same! Parental influence appears to be much stronger if parents model good eating habits, consuming plenty of fresh fruits and vegetables rather than just talking about how one should eat them.)
Cultural influences in families can also affect what you eat. Studies of Hispanic adults in this country show that those who are less acculturated to American habits and stick more to their traditional customs consume more fruit, rice and beans, and whole milk, whereas those who are more acculturated eat more fast food, snacks, sugar, sugar-sweetened beverages, and foods with added fats. One small study that compared the eating habits and feeding practices of French and American parents found an interesting twist: In the U.S., parents more often use food as a reward or to regulate a child’s emotions than do parents in France.
But by far the most significant parental influence on eating habits is the family meal. Family dinners are a foundation of healthy food choices. Children who eat dinner with their families every day eat more fruits, vegetables, and whole grains and more calcium- and iron-rich foods. They also drink less soda and eat less fried food and fewer saturated fats and transfats. Moreover, studies show that teens who eat more than three family meals a week are less likely to skip breakfast and more likely to eat fewer fast-food meals. The effect is lasting. One study revealed that young teens who eat regular family meals in middle school have better quality diets and eating patterns five years later when they’re in high school.
As for the influence of spouses and significant others: We tend to eat what they eat. This makes sense, of course. Once people become involved in a relationship, they often shop, cook, and eat together, typically merging their food choices, especially at dinner. One study showed that dietary changes for women followed a pattern, with women in a heterosexual relationship eating meat more often and drinking higher-fat milk than they would if they were alone.
Our food choices are also affected by our dining companions outside of family. When researchers looked at the way adolescents choose items from a typical lunch menu, they found that the students admitted that their peers’ choice swayed their own choices. Most often they opted for soda, chicken, hamburgers or cheeseburgers, and fries. However, they did try to balance their unhealthy lunches with healthier, more nutritious family dinners. (More proof that family dinners matter!)
And here’s a twist for women: As it turns out, we consume more calories if our dining companions are also women. Researchers who studied students at three large university cafeterias in Ontario, Canada, found that women were more likely to choose foods with higher calories when they were eating with members of the same sex. On average, women who ate with other women consumed 665 calories during their meal; when they dined in groups of four women, their intake jumped to an average of 800 calories. But women who ate with a lone male companion consumed only about 550 calories and—in a reversal of the “more the merrier” trend with all-women groups—those who ate with a group of men took in fewer calories, only 450.
The point is, social networks are powerful forces in shaping our ideas about our health and also, our health-related behaviors. But it’s not as simple as that. While social influences are strong, genes and environment also have supporting roles.
Deanne’s story points out just how complicated the interactions can be between genes, environment, and social influences. She had tried many times to trim down, she says—to watch what she ate and to exercise regularly. But she always fell back into her old habits, being inactive, eating large portions at meals and snacking on junk food, cookies, chips, candies. At age 33, she weighed 268 pounds and suffered from high blood pressure, high cholesterol, and frequent migraine headaches. That year, 1999, two things happened.
“It was the summer, and I had taken my nephew to the amusement park,” Deanne recalls. “On one ride, they kept trying to bring the bar down over me, and then it would spring back up. The staff asked me to get off the ride because the bar wouldn’t close. I was so embarrassed. I knew I had to do something, but still I put it off. That winter, I was working in a hospital, and I helped move people who were too heavy to get about themselves, and I thought to myself, ‘I could be looking at myself in 20 years’ time—unless I do something now.’”
These events triggered some astonishing changes in Deanne’s life. But how did she become one of those 35 percent of women in the U.S. who are obese? The answer lies in the socioecological model, the complex interplay between the individual, our relationships, our community, and societal factors.
Socioecological Model
YOU, THE INDIVIDUAL
Beyond your social networks, what personal issues affect how much you eat and your level of physical activity?
Genes, for certain. We’ve known for some time that body weight is a matter of balance between food intake and energy output. Among the intriguing new insights we have learned lately is that this balance is controlled not by conscious willpower, but by a powerful, unconscious biological system. A significant piece of this system is genes, which influence everything from taste preferences and appetite to how much fat we burn.
To date, scientists have identified 198 genes that are related to body weight. We all possess these genes. They affect our tendency to eat sugary, fatty foods, to store fat (rather than burn it), and whether or not we want to run around or prefer to spend time on the couch. They are potent forces, and we’ve had them in place in our DNA for more than 10,000 years. They evolved when we were hunter-gatherers facing scarce seasonal food supplies, to promote eating and reinforce its pleasures and to conserve fat and reduce energy
