A 2007 study spawned a wave of sensational headlines after researchers at Harvard Medical School announced that obesity might be contagious. They found that if your spouse or a friend becomes obese, you are significantly more likely to become obese, too. But a recent study at Marquette University may have discovered that the opposite is true for college freshman.
The idea that obesity could be moving between friends and spouses like the flu didn’t sound quite right to Kandice Kapinos, assistant research scientist at the University of Michigan Institute of Social Research. It seemed more likely that people simply marry and befriend similar individuals in the first place.
Kapinos and her colleagues Olga Yakusheva and Marianne Weiss decided to find out if this contagious effect was seen in relationships you don’t choose.
“What we did was exploit the fact that most college campuses tend to randomly assign roommates,” Kapinos says. “We looked to see if randomly assigned roommates affected weight gain over the course of the year.”
Kapinos, Yakusheva, and Weiss surveyed college females at Marquette University in Milwaukee at the beginning and end of their freshman year about their height and weight. They also asked about their diet and exercise habits and whether or not they were trying to lose weight. Then they compared the surveys of roommates.
The results, which have yet to be published, may at first seem counter-intuitive: freshmen with thin roommates gained more weight than average over the year, and freshmen with overweight roommates gained less. This contradicts the many studies that show the opposite effect — that your weight usually changes along with your peers.
“So we dug a bit deeper and looked at the behaviors,” Kapinos says. “The heavier females in our study are more likely to be watching their weight, dieting, exercising, and engaging in weight-loss behavior. What we think is ‘contagious’ are the behaviors and not the weight.”
Wendi Gardner, associate professor of social psychology at Northwestern University, says the sample size of this study, 187 students, is too small to draw any major conclusions, and the findings will need to be replicated by other scientists. Nevertheless, she says it’s definitely possible to “catch” a behavior from someone else, even a stranger.
“We adopt other people’s goals and motives completely unconsciously,” Gardner says. “These effects happen outside of our awareness.”
Gardner studies the human need to belong and be included, and all the unconscious things we do to fit in. Humans are wired to imitate other people, from their facial expressions to their habits, because doing so helps everyone get along smoothly and understand each other better, Gardner says.
Weinberg sophomore Claire Maby says her freshman year roommate assumed everyone went to the gym regularly. Her roommate’s attitude about exercising eventually influenced Maby to start going to the gym, too.
“My roommate was super thin and in shape, and she would go to the gym all the time,” Maby says. “So I thought, okay, I’ve got to do that, too. I think I was happy that I picked that up in the end. I might go to the gym more than she does at this point.”
Gardner’s research shows that the urge to imitate others is amplified when you are left out of a group. When you feel excluded, your ability to decode facial expressions and understand someone’s tone of voice is enhanced. And “you’re more likely to mimic the next person you’re interacting with, which will make them like you more,” Gardner says.
Lauren Lindstrom is experiencing the Marquette study first hand as a freshman in Medill.
“It’s a different dynamic living with people you’re not related to,” Lindstrom says. “You lived with the same people for 18 years, and then suddenly you’re with brand new people. I hadn’t really thought about picking up other people’s habits, but I guess it’s probably bound to happen eventually.”
Our tendency to copy other people may explain how someone can unconsciously pick up bad habits from a roommate. If your roommate has been naturally thin all her life, she may see no problem with ordering a pizza three nights a week. And you start to see no problem with it either, because as Gardner points out, humans have evolved to want to conform to other people.
“The reason humans have risen to be apex predators is because we’ve been able to coordinate our behaviors and our actions,” Gardner says. “We’re intelligent, but we’re not big, and we’re not scary.”
The ability to mesh our thoughts and goals with those of other people is very helpful if you need to, say, work as a group to bring down a woolly mammoth, Gardner says, “but can have some interesting consequences in this day and age.” And for some freshmen, those interesting consequences might be showing up on the scale.