- Posted March 31, 2026
Teens' Sleep Patterns Affect Their Diet, Exercise, Study Says
Teenagers might be known for being night owls, but they’ll be healthier if they can get to bed earlier, a new study says.
Teens who stay up late and sleep the morning away are more likely to eat more and be less physically active, especially when school is in session, researchers report in the April issue of the journal Sleep Health.
“Sleep timing — when teens go to bed and wake up — had the biggest influence on sedentary and eating behavior in teens,” senior researcher Julio Fernandez-Mendoza, a professor of psychiatry and behavioral health at Penn State College of Medicine, said in a news release.
“It’s something parents need to pay attention to — and protect — during critical developmental years like adolescence,” he said.
The body’s internal clock not only regulates when a person sleeps and wakes, but other processes like metabolism and movement, researchers said in background notes.
Because of that, going to bed late can influence a person’s sense of hunger, food cravings and desire to move or rest, researchers said.
“We have the tendency to separate sleep, diet and physical activity as three distinct things, but we can’t isolate them from one another. We have to think about them together,” Fernandez-Mendoza said.
Most teens don’t get the eight to 10 hours of sleep recommended by experts, researchers said. In part, that’s because their internal clocks conflict with school hours.
Kids naturally start sleeping later in the evening and waking later in the morning as they grow into their teenage years, but schools require them to rise earlier than their body clock would prefer.
For this study, researchers tracked the health of 373 kids participating in a long-term health study. Some of the kids were evaluated while they were in school, and others while they were on break from school.
The research team monitored multiple aspects of the teens’ sleep – bedtime, wake time, total sleep time, sleep midpoint, sleep efficiency and time in bed. They also tracked food and snack intake, as well as physical activity.
“Sleep is more than just how long a person sleeps but there aren’t many studies that look at this issue from a holistic perspective beyond how much sleep teens get,” lead researcher Pura Ballester-Navarro said in a news release. She’s a professor at San Antonio Catholic University of Murcia in Spain.
Results showed that teens who were night owls – getting to bed after midnight and rising after 8 a.m. – consistently consumed more calories, ate more carbs and got less physical activity.
These teens snacked more and tended to skip breakfast, since they woke up late. Instead, they ate lunch, dinner and a late-evening snack that was often less healthy than a typical breakfast.
This effect was twice as strong when school was in session, possibly due to the conflict between their body clocks and school schedules, researchers found.
On the other hand, this relationship between sleep and unhealthy behaviors weakened when school was out of session, perhaps because teens had more flexibility in their schedules, researchers said. However, kids tended to snack more when they weren’t in school.
“When the timing of teens’ eating and snacking is out of sync with their normal biological clock, it further dysregulates their sleep,” Fernandez-Mendoza said.
Teens also had less healthy eating and activity patterns if their sleep varied, with alternating nights of shorter and longer amounts of sleep.
Parents might help their teens by encouraging them to get to bed earlier, researchers said.
“A consistent sleep routine is a powerful tool,” Ballester-Navarro said.
More information
The National Sleep Foundation has more on sleep recommendations for teenagers.
SOURCE: Penn State, news release, March 26, 2026
