A study shows that teens are more likely to be overweight if they sleep less than eight hours per night during the school week. Their odds of being overweight increase as their average self-reported sleep duration decreases.
For teens in the study group the odds of being overweight increased by more than 2.5 times if they reported sleeping for an average of five to seven hours on school nights. Sleeping less than five hours per night resulted in a skyrocketing of the risk. These teens were about eight times more likely to be overweight.
The results were adjusted to isolate short sleep duration from other potential factors. These factors included irregular eating, health status and caffeine intake.
The study was published online on April 18 before coming out in print in the journal Sleep and Breathing. It was conducted by researchers at Case Western Reserve University in Cleveland, Ohio.
The study group involved 509 students. They attended a public high school in the suburb of Bay Village, Ohio. All of the students were between 14 and 18 years of age. They completed a questionnaire between November and December 2004.
The majority of students were from middle-class families. Ninety-four percent were Caucasian. The researchers caution that the study results may not apply to other population groups.
Data on gender, age, height and weight were used to classify students as overweight. This was based on the Centers for Disease Control growth charts.
Twenty percent of the students were overweight. About 70 percent of overweight students were male. Eating behavior and level of physical activity were similar between overweight students and their peers.
The researchers were intrigued to find that overweight students had a higher rate of caffeine intake. They suggest that overweight teens may use caffeine to cope with daytime sleepiness caused by sleep deprivation.
According to the American Academy of Sleep Medicine, most teens need about nine hours of sleep per night to feel alert and well rested. But only ten percent of teens in the study reported an average sleep time of more than eight hours on school nights.
The majority of students reported a moderate sleep duration of six to eight hours of sleep on school nights. Nineteen percent reported getting less than six hours of sleep per night. Four percent reported sleeping less than five hours per night.
Students slept more on weekends, perhaps trying to “catch up” on sleep that was lost during the week. Fifty percent of students slept more than eight hours per night on weekends.
The researchers also reviewed the link between obesity and sleep by citing other recent studies on the subject. National obesity rates have increased as the average sleep durations reported in surveys have decreased. Childhood obesity has tripled over the last 30 years. The proportion of teens who sleep less than seven hours per night doubled between 1960 and 2001.
Research also shows that sleeping less may cause people to eat more. Studies have found that short sleep duration is related to lower levels of leptin and higher levels of ghrelin. Leptin is a hormone that helps suppress your appetite and increase your metabolism. Ghrelin is a hormone that stimulates appetite. So when you are sleep deprived, the hormone to suppress hunger is low and the one to stimulate appetite is high.
Both genetics and lifestyle contribute to childhood obesity. High-fat diets and inactivity are key risk factors for weight gain. But efforts to reduce obesity with exercise and nutrition have had limited success.
The researchers conclude that sleep should be an important part of any obesity intervention. Healthy sleep habits also should play a role in obesity prevention and weight management.
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Reviewed by Rose Franco, MD
Updated August 22, 2007