Freshmen women who live with a heavier-than-average roommate are less likely to gain weight themselves, a University of Michigan study found.

The study discovered heavier roommates are more likely than average-weight women to diet, exercise, take weight loss supplements and purchase meal plans that limit access to food.

And those behaviors rub off. According to researchers, those with heavier roommates will gain a half a pound on average, while those with average-weight roommates gain 2.5 pounds.

The “Freshman 15” is a myth — the typical freshman will gain 2.5 to 6 pounds.

"It's not really the weight of your roommate that's important, but the behaviors your roommate engages in," Kandice Kapinos, an assistant research scientist at the U-M Institute for Social Research, said in a written statement. "These behaviors are what may really be 'contagious.'"

Kapinos partnered with Marquette University economist Olga Yakusheva to assess college weight gain.

The small study included 144 participants who were randomly assigned roommates. The study authors quizzed them about their eating and exercise habits.

Obesity has increased in adults between the ages of 18 and 29 by 96 percent between 1988 and 2006. That’s the largest percentage increase of all age groups, according to the researchers.

With numbers like those, Kapinos said she hopes the research will have practical implications for both university administrators, as well as public health efforts geared toward reducing obesity.

Juliana Keeping is a health and environment reporter for AnnArbor.com. Reach her at julianakeeping@annarbor.com or 734-623-2528. Follow Juliana Keeping on Twitter