TUESDAY, Oct. 25 (HealthDay News) -- Teens who don't get enough sleep may find themselves putting on extra pounds and boys, in particular, may be at risk for obesity, new research suggests.

In the study, researchers surveyed 108 male and 147 female students at a Texas high school and found that the average sleep time on weekdays was 6 hours 32 minutes for males and 6 hours 30 minutes for females. The average sleep time on weekends was 9 hours 10 minutes for males and 9 hours 22 minutes for females.

Average body mass index (or BMI, a measurement that takes into account height and weight) was 3.8 percent higher for males who slept 7 hours or less on weekdays than for those who slept more than 7 hours, and 4.7 percent higher for females who slept 7 hours or less on weekdays than for those who slept more than 7 hours, the investigators found.

The researchers also noted that getting less than 8 hours sleep per night was associated with obesity in male teens, with the fewest hours of weekday sleep associated with the highest BMI. But the study didn't find a link between obesity and weekday sleep hours in teenage girls.

The study was slated for presentation Oct. 24 at the annual meeting of the American College of Chest Physicians (ACCP), in Honolulu.

"Sleep is food for the brain. When teens do not get enough sleep, they fall asleep in class, struggle to concentrate, look and feel stressed, get sick more often, and do not meet their obligations due to tiredness," study author Lata Casturi, of Baylor College of Medicine Sleep Center in Houston, said in an ACCP news release.

"Teens who sleep fewer than eight hours may also consume more calories than those who sleep more than eight hours. Therefore, they have a higher risk for obesity and associated health problems, including high blood pressure, heart disease and stroke," Casturi added.

While the study found only an association between sleep and weight, which does not prove cause-and-effect, the authors noted that researchers have found that lack of sleep causes a decrease in the hormone leptin (which tells the brain when you're full) and an increase in the hormone ghrelin (which stimulates appetite).

"When you don't get enough sleep, it drives leptin levels down, which means you don't feel as satisfied after you eat. Lack of sleep also causes ghrelin levels to rise, which means your appetite is stimulated, so you want more food," co-author Dr. Radha Rao, of DeBakey VA Medical Center in Houston, explained in the news release. "The two combined can set the stage for overeating, which in turn may lead to weight gain."

The sex-related difference in the association between lack of sleep and obesity may be due to different growth rates and hormone secretion in boys and girls during puberty, the authors suggested in the news release.

"The sleep factors that impact metabolism may increase weight gain differently in the two sexes," Casturi added.

Because this study was presented at a medical meeting, the findings should be viewed as preliminary until they are published in a peer-reviewed journal.

More information

The Nemours Foundation outlines how much sleep teens need.