College freshmen beware — the "freshman 15," the eating binge long speculated to pile on 15 pounds during the first year of college, could be real.

According to a new study by a Cornell University professor and his former student, college freshmen gain an average of 4.2 pounds just during their first 12 weeks on campus.

"Significant weight gain during the first semester of college is a real phenomenon, with breakfast and lunch at all-you-can-eat dining facilities accounting for 20 percent of the weight gain," says David A. Levitsky, professor of nutritional sciences and of psychology at Cornell.

Other significant predictors of weight gain, he says, include the number of evening snacks, the number of meals consumed on weekends, the consumption of "junk" foods and recent dieting (recent dieters, he notes, are more apt to gain weight).

Levitsky and his colleagues believe that the freshman weight gain could, in fact, be the same phenomenon that is contributing to the epidemic of obesity among all Americans -- that a relatively small increase in calories each day or week has the profound cumulative effect of adding a significant amount of weight over the years.

For an honors thesis, former Cornell student Craig A. Halbmaier '01 worked with Levitsky and research associate Gordana Mrdjenovic to assess the weight gain of 60 Cornell first-semester students (85 percent of them female). Levitsky presented the findings July 16 in Groningen, the Netherlands, at the annual meeting of the Society for the Study of Ingestive Behaviors, an international group of researchers studying eating and weight.

The students in the sample, recruited from two large introductory courses, were weighed at the beginning and end of their first 12 weeks of college. Each filled out a questionnaire about eating, exercise and sleeping habits.

The freshmen, on average, gained about 0.3 pound per week, which is almost 11 times more than the weekly weight gain expected in 17- and 18-year-olds and almost 20 times more than the average weight gain of an American adult. "American adults gain about 8 grams [about one-fourth of an ounce] a week, a rate of increase that is considered an epidemic by many as it easily leads to obesity," says Levitsky. The college freshmen in the study gained an average of 158 grams (about 5 1/2 ounces) a week. That's the equivalent of ingesting about 174 more calories a day than energy expended, and the approximate calorie equivalent of two apples or a plain bagel. "This amount represents a relatively small change in behavior, yet it has enormous cumulative consequences on weight," Levitsky says.

"Although the use of all-you-can-eat dining halls may be effective as a recruiting technique for colleges, these food bars may be responsible for much of the weight gain we see in freshmen," Levitsky says. He notes that various studies show that humans tend to eat the amount of food they are served, and when students take large portions, they are apt to consume them. Easy access to junk food in dorms and around campus also contribute to excessive weight gain, because, Levitsky points out, humans do not appear to compensate for between-meal snacks.

If the campus weight gain is indeed related to the rise in obesity nationwide, "then it should be possible to study various methods and techniques that might prevent the freshman weight gain in the hope that they might be effective in the general population to reduce or even reverse the trend towards increasing body weight and obesity in the public," Levitsky says.

The study was supported, in part, by the New York State College of Human Ecology at Cornell.