Make healthy behaviors a part of your day now, and they'll stay with you as you get older.

College students who don't use trays may avoid overeating.

RODALE NEWS, EMMAUS, PA—College weight gain is hard enough to combat, and a new study finds that young women may have a harder time warding off the notorious "freshman fifteen" than their male classmates. Women in that age group don't seem to get as much exercise as they used to. The study, which will be published in the October issue of the American Journal of Public Health, finds that over the past 23 years, young women have cut down on exercise and healthy eating, allowing adolescent obesity to linger long into young adulthood.

THE DETAILS: The researchers collected data from young adults, ages 19 to 26, who had participated in a long-running survey of health behaviors. Using surveys administered to a total of 17,314 young adults over 23 years, they looked at trends related to exercise, eating behaviors, sleep (getting at least seven hours), and time spent watching television. Data showed that exercise rates among young women have declined more rapidly than those among young men, leading the researchers to believe that the trend may be a good explanation for gender disparities in obesity.

WHAT IT MEANS: When it comes to fighting college weight gain—or any weight gain for anyone of college age—coasting doesn't help. It takes deliberate effort to develop healthy habits that will last. "At this point in their lives, young adults are on their own, typically for the first time," says lead author Philippa Clarke, PhD, research assistant professor in the Institute for Social Research at the University of Michigan. "During these formative years, they're undertaking their own healthy behaviors outside the parents' home," she adds, "and the behaviors they develop are indicative of what they maintain over time."

Warding off the freshman (or sophomore or junior or senior) fifteen can be difficult, and losing it once you've graduated can be even harder. But gaining weight during young adulthood isn't just a problem for the college-bound, says Clarke. In her study, women with the lowest socioeconomic statuses were the least likely to exercise or eat healthy. Similar challenges may affect young people without hefty salaries that afford gym memberships and other healthy lifestyle options.