Being a college freshman is fun, sure, but it can also be a time of big changes.

Among those changes? Finding one’s wardrobe seemingly shrunk overnight.

In a new study, researchers from George Mason University and the College of William and Mary say they have a better idea why the much-talked-about “freshman 15” happens.

But first, to clarify a few things: College freshmen, on average, tend to gain between 3 and 8 pounds, not 15. Male students tend to gain a little more than female students.

In their new study, the researchers say that college student life, with its dining halls, unstructured schedules and emphasis on socializing, is practically a recipe for weight gain.

The study involved a diverse mix of more than 40 college students in the northeastern United States, ranging in age from 18 to 25 years old. They agreed to log their every meal and snack with the help of a food and beverage tracking app. They also completed daily surveys to document their eating behaviors, where they ate, their mood and stress levels.

Over the course of nearly 3,200 meals, drinks and snacks, the data showed clear patterns. Students most often consumed more when they were with at least one other person or in a group. More calories were consumed when they ate in places like dining halls or restaurants.

When students ate alone or at home, they tended to eat less.

The male college students were far more likely to consume more while in a group, and less likely to realize they had done so.

So, the circumstances around food made a big difference in consumption, as did the students’ moods and stress.

It’s certainly something to chew on.