Late Sleep Linked to Poor Diet, Sedentary Teens

Study finds sleep timing, not just duration, influences eating habits and physical activity in adolescents.

Mar. 27, 2026 at 7:12am

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A new study from Penn State College of Medicine found that when teenagers go to sleep and when they wake up may be the driving force behind what they eat and how much they move. Teens who went to sleep later and woke up later were more likely to consume more calories, snack more, and be less physically active - especially when in school compared to on break. The findings suggest that sleep could be a key factor in protecting heart health in adolescents.

Why it matters

Sleep is a potential risk factor for cardiometabolic health, even in teens. The study highlights how sleep timing - when teens go to bed and wake up - has the biggest influence on sedentary and eating behavior in teens, which are important for cardiovascular and metabolic health. Understanding the connection between sleep, diet, and physical activity in adolescents can help parents and caregivers develop strategies to promote healthier habits during this critical developmental stage.

The details

The study examined how different aspects of sleep, beyond just hours slept, are associated with diet, exercise, and sedentary behavior in 373 adolescents aged 12-23. Researchers monitored sleep timing, duration, regularity, and quality using wearables, surveys, and in-lab studies. They found that "night owl" teens who went to bed after midnight and woke up after 8am consistently ate more calories, particularly carbohydrates, snacked more, and were more sedentary. Highly variable sleep duration was also linked to less physical activity. These relationships were stronger when school was in session, as teens had to fight their natural biological rhythms to sync with external schedules.

  • The study included participants between the ages of 12 and 23, with an average age of 16.4 years.

The players

Julio Fernandez-Mendoza

The Edward O. Bixler professor of psychiatry and behavioral health at Penn State College of Medicine and senior author of the study.

Pura Ballester-Navarro

Professor at Universidad Católica San Antonio de Murcia in Spain and first author of the study.

Penn State College of Medicine

The institution where the study was conducted.

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What they’re saying

“Sleep is a potential risk factor for cardiometabolic health, even in teens. Sleep timing — when teens go to bed and wake up — had the biggest influence on sedentary and eating behavior in teens. It's something parents need to pay attention to — and protect — during critical developmental years like adolescence.”

— Julio Fernandez-Mendoza, Edward O. Bixler professor of psychiatry and behavioral health

“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.”

— Julio Fernandez-Mendoza, Edward O. Bixler professor of psychiatry and behavioral health

“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.”

— Pura Ballester-Navarro, Professor

“When the timing of teens' eating and snacking is out of sync with their normal biological clock, it further dysregulates their sleep.”

— Julio Fernandez-Mendoza, Edward O. Bixler professor of psychiatry and behavioral health

“A consistent sleep routine is a powerful tool.”

— Pura Ballester-Navarro, Professor

What’s next

The researchers suggest that when trying to encourage healthy eating and physical activity in adolescents, targeting the regularity and timing of their sleep could be a key strategy. For example, parents and caregivers can focus on earlier bedtimes, longer sleep duration, and consistent sleep schedules during the school year while reducing late-night snacking and sedentary behavior when kids are out of school.

The takeaway

This study highlights the important connection between sleep, diet, and physical activity in adolescents. By understanding how sleep timing and variability influence eating habits and sedentary behavior, especially during the school year, parents and caregivers can develop targeted strategies to promote healthier lifestyles and protect the cardiometabolic health of teens during this critical developmental stage.