Besides being well rested for school, there’s another reason for teens to hit the hay early: going to bed later during the workweek is associated with weight gain over time.
The study, published in the journal Sleep, analyzed data on more than 3,300 teens and young adults recorded over a span of 15 years.
“Obesity is obviously growing among adolescents and adults, and there’s also an epidemic of lack of sleep and later bed time preference in teens,” study author Lauren Asarnow, a doctoral candidate at the University of California, Berkeley, told CBS in an interview.
The study showed a 2.1 point increase in body mass index (BMI) for every hour of sleep lost, gained over a five year span.
“Conceivably, if you’re going to bed an hour later, over time you could be shifting BMI categories from normal to overweight,” Asarnow said. “So even a two-point increase could be clinically significant.”
Interestingly, the length of sleep time had no relationship between itself and BMI – meaning that going to sleep late isn’t cancelled out by sleeping in.
There’re a few theories as to the sudden bump in belly weight from late bedtimes, including eating late night snacks, and skipping breakfast altogether, which is surprisingly associated with weight gain.
“The good news is sleep is a highly modifiable,” Asarnow explained. “If you could shift bedtime in the teenage years, you can create good sleep habits and maybe prevent weight gain over time.”