The myth of the dreaded “freshman 15,” it seems, is greatly exaggerated. That’s the average amount of weight that college freshmen supposedly gain after moving into dorms where beer and pizza are more plentiful than fresh fruits and vegetables. But while new college students may not gain as many as 15 lbs., a new study shows that their weight is still heavily influenced by dormitory life.
Researchers at University of Michigan and Marquette University found that women who lived with heavier-than-average roommates gained less weight — only half a pound — during their freshman year than women who lived with slimmer partners. They gained about 2.5 lbs.
It turns out the average new college student gains between 2.5 and 6 lbs., at most just shy of one half of the legendary freshman 15. But the fact that students with heavy roommates gained less than average seems counterintuitive, not to mention contrary to the latest research that suggests obesity may actually be socially contagious. Data show that people who are related to or are friends with obese people are more likely to be obese themselves. (More on Time.com: Explaining the Gender Gap: Obesity Costs Women a Lot More Than Men)
But Kandice Kapinos, an assistant research scientist at University of Michigan, says the result isn’t as surprising as it might seem, once you look more carefully at the way college students live.
While the study was small, involving only 144 female students, it had the advantage of relying on the random room assignments that the Marquette University housing office used to pair incoming freshmen. At the beginning of the year, the students were asked about their eating and exercise habits — whether they were on a diet, which meal school meal plan they had purchased, how often they used the gym, and whether they used weight loss supplements.
This gave the researchers an idea of how the students addressed their weight. In the study, the average weight of the students was 139 to 140 lbs., and those who were heavier were more likely to be on a diet, use a restricted meal plan, or exercise more.
Such behaviors, says Kapinos, and not the roommate’s weight itself, were what influenced the students. “We expected the social effect to be that if you had a heavier roommate, you would weigh more at the end of the year,” she says. “But if you look at the behaviors, our results makes sense. Those who weigh more are trying to lose weight, and it makes sense that the pure peer effect is actually in the behaviors.” (More on Time.com: Can Catching a Cold Make You Fat)
She stresses that the results are still preliminary, and involve only a small group of students at a single university. But they confirm the strong social and peer influence on body weight. While previous work found a strong link between having obese friends and being obese yourself, Kapinos says part of that effect may be due to the fact that people tend to be attracted to those who share similar features and perspectives. You chose your friends, she notes, and relatives share genetic predisposition that may explain their similar weights.
But college roommates are randomly assigned, so the current study may be exposing the true influence that peers can have on something as complicated as body weight. And that influence, she found, extends from peers’ behaviors to the physical environment as well.
In another study, Kapinos and her colleague found that students living in dorms with onsite dining halls gained more weight after their freshman year than those living in cafeteria-free quarters. Again, they found this effect among those who were randomly assigned to different living situations, so it suggests that where you live and who you live with can have a weighty effect on your body size. (More on Time.com: America Is Officially the Fattest Developed Country in the World)