The study included 240 teenagers between the ages of 16 and 19 who were part of a larger study on sleep habits and health. The researchers measured the teens’ sleep duration using wrist monitors, and on two separate occasions asked them to list the foods they’d eaten in the previous 24 hours.
The teens averaged about 7.5 hours of sleep each weeknight—well shy of the nine hours the American Academy of Sleep Medicine recommends for this age group. Only about one-third of the teens slept for eight hours or more.
Compared to their better-rested peers, sleep-deprived teens got about 2% more of their daily calories from fat and 3% fewer calories from carbohydrates, the study found. And the teens who slept less than eight hours were more likely to get their calories from snacks—especially the girls.
“This study goes out into the real world and finds that short sleep is…associated with dietary choices and increased appetite,” Knutson says.
Even though snacking can be a part of a healthy diet, eating at times of day that are misaligned with the body’s clock can alter metabolism and make a person more likely to gain weight, according to Dr. Redline. More of the sleep-deprived teens consumed a significant amount of calories between the hours of 5 a.m. and 7 a.m., she notes.
“Teens tend to be what we call ‘phase-delayed,’ so their body’s natural tendency is to push them towards later bedtimes,” says Dr. Redline. “Then if school is pushing them to wake up early, they’re going to be sleep-deprived, and perhaps eating in the very early hours when their metabolic system isn’t really geared up to deal with that many calories.”
The study findings should serve as a reminder to teens and parents alike that sleep—not just diet and exercise—is a key part of a healthy lifestyle, Knutson says.
“We need to let parents know that bedtime is important for the health of their kids,” she says.
