A later bedtime could have a serious effect on your health.

Teen at night with laptop and headphones
Credit: Nico De Pasquale Photography/Getty Images

If staying up past midnight has become a nightly routine (we're looking at you, Netflix), it might be time to consider winding down earlier. New research has identified a link between later bedtimes and weight gain in teens—and every hour counts.

Lack of sleep has been associated with an increased appetite (and a greater risk for developing Type 2 diabetes), but the new study, published in this month’s edition of the journal Sleep, suggests the time teens go to bed could be affecting the number on the scale as well.

Researchers from the University of California, Berkeley, analyzed data from the National Longitudinal Study of Adolescent Health, which tracks teenage behaviors. They compared the bedtimes and body mass indices (BMIs) of 3,342 teenagers from 1994 to 2009, specifically focusing on three life stages: the onset of puberty, their college-age years, and young adulthood.

Every extra hour the teenagers stayed awake was linked to a 2.1 point increase in their BMI over a five-year period. The amount they exercised, their screen time, and the number of hours they slept did not affect the results—though fast food eating habits were identified a potential factor.

"These results highlight adolescent bedtimes, not just total sleep time, as a potential target for weight management during the transition to adulthood," Lauren Asarnow, lead author of the study, said in a statement.

An earlier bedtime could help teens get the sleep they need—a topic that has garnered so much attention, in fact, that the U.S. Center for Disease Control and Prevention has recommended delaying school start times. Adolescents who hit the hay early could also "set their weight on a healthier course as they emerge into adulthood," Asarnow said.