Teenagers who don't get enough sleep may have a higher risk for obesity, according to a recent study.

Researchers from the Mailman School of Public Health at Columbia University and the University of North Carolina Gillings School of Public Health found that the risk of being obese by age 21 was 20 percent higher among 16-year-olds who got less than six hours of sleep a night, compared with their peers who slumbered more than eight hours.

"Lack of sleep in your teenage years can stack the deck against you for obesity later in life," Shakira Suglia, researcher and assistant professor of Epidemiology at the Mailman School, said in a statement. "Once you're an obese adult, it is much harder to lose weight and keep it off. And the longer you are obese, the greater your risk for health problems like heart disease, diabetes, and cancer."

For the study, Suglia and her colleagues analyzed health information from more than 10,000 American teens and young adults between the ages of 16 and 21 as part of the National Longitudinal Study of Adolescent Health. Information on height and weight and sleep was collected during home visits in 1995 and 2001.

They found that nearly one-fifth of the 16-year-olds reported getting less than six hours of sleep. This group was 20 percent more likely to be obese by age 21, compared to their peers who got more than eight hours of sleep. While lack of physical activity and time spent watching television contributed to obesity, they did not account for the relationship between sleeplessness and obesity.

"The message for parents is to make sure their teenagers get more than eight hours a night," Suglia added. "A good night's sleep does more than help them stay alert in school. It helps them grow into healthy adults."

Daytime sleepiness and fatigue are known to affect what and how people eat, by altering appetite and stimulating cravings. Energy levels may also play a role.

For the sleep-deprived, ordering calorie-dense fast food is easier than preparing a nutritious meal. Information on what the teens ate was not captured in the surveys, although it could play a role. Future research may look at whether, for example, soda consumption is a factor in sleeplessness and, in turn, obesity.

The findings were recently published in the Journal of Pediatrics.