Does your teen stay up past midnight and sleep late? This habit may do more than just make your mornings rough. new He studies A study from Penn State College of Medicine found that teens who maintained later bedtime and wake times were more likely to consume more calories, snack more, and be less physically active.
What the study found
The researchers studied 373 teens from the Penn State Children’s Cohort, a long-term population-based study established in 2000. Participants ranged in age from 12 to 23 years, with an average age of 16.4 years.
Published in the magazine Sleep healthThe study went beyond simply tracking how long teens slept. The researchers monitored sleep timing, regularity, and quality using wrist wearable devices, self-administered questionnaires, and in vitro sleep studies. They also tracked food intake, snacks, and physical activity.
Teens who usually went to bed after midnight and woke up after 8 a.m. consumed more calories, especially from carbohydrates, and were more sedentary. They also ate more snacks, especially later in the day and at night. Because they slept at home, many of them skipped breakfast. Instead, they ate a late-evening snack that tended to be less healthy than a typical breakfast. Teens who had highly variable sleep, switching between short and long nights, were less physically active overall.
Why does sleep timing affect eating and activity? The body’s internal clock does more than just regulate sleep. It also regulates metabolism, hunger, food cravings, and the desire to move or rest. When teens have late or irregular sleep schedules, it can throw off those schedules.
These patterns were about twice as strong during the school year. When teens have to wake up early for school while their bodies force them to stay up late, it leads to a cascade of unhealthy eating and inactivity. During breaks, poor communication. But snacking still increases when kids are out of school.
Why sleep matters in teens
So why do so many teens struggle with sleep? A lot of it comes down to biology. During adolescence, the body’s circadian rhythm and biological sleep change to produce later sleep and wake times. Teenagers are forced to stay up later and sleep later.
However, early school start times work against this natural transition and can reduce sleep, impact learning, negatively impact health, and impair driving safety. AASM recommend Middle and high school start times are 8:30 a.m. or later. More than half of Americans (54%) say school starts too early for these students, and 90% of parents say early start times affect their children’s ability to get enough sleep on school nights.
The numbers tell the story. About 78% of high school students and 34% of children do not get enough sleep on the average school night. AASM recommend Teens ages 13 to 18 get 8 to 10 hours of sleep each night to promote optimal health.
When students consistently fail to achieve this goal, it can lead to behavior and learning problems, obesity, diabetes, high blood pressure, and mental health problems. On the other hand, getting enough quality sleep helps students excel in the classroom, perform better in sports, feel more positive, and maintain a healthy weight.
Healthy sleep is more than just the total number of hours. It also requires proper timing, daily regularity, good quality, and the absence of sleep disturbances.
This video explains why teens are biologically inclined to stay up late, the challenges they face getting enough sleep, and tips on how to build positive sleep habits.
What parents can do
Penn State researchers suggest that improving the timing and regularity of teens’ sleep could be a key strategy for overall healthier habits.
Parents and caregivers can help by encouraging earlier bedtimes, longer sleep duration, and consistent sleep schedules, especially during the school year, while reducing late-night snacking and sedentary behavior when children are at recess. Read more tips for establishing it Healthy sleeping habits.
For more information about healthy sleep for teens and resources for students and parents, visit the AASM’s Student Sleep Health Week page. Student Sleep Health Week will take place September 14-18, 2026.
Medical review by Ahmed Saleh, MD
