College cafeterias often get the blame for the “Freshman 15” — a reference to the weight many incoming students gain their first year in school. But new research suggests it’s actually all those all-nighters — spent studying and otherwise — that are the culprit.

The findings, published in the Behavioral Sleep Medicine looked, have implications for anyone who suffers sleep deprivation, The New York Times reports.

For the study, researchers tracked the sleep habits of 132 first-year students at Brown University. After nine weeks, more than half of them had gained nearly six pounds, which researchers correlated with poor sleep habits.

Optimally, experts say, teenagers need about nine hours and 15 minutes a night. But the freshmen in the study averaged about seven hours and 15 minutes.

Another study, published earlier this year in the Public Library of Science journal PLOS ONE, found that when teens are sleep-deprived, they more readily reach for candy and desserts.