Researchers have reported that children and teenagers who do not get enough sleep, particularly REM sleep, are more likely to be obese. REM or rapid eye movement is the sleep when we dream. Dr. Xianchen Liu of Western Psychiatric Institute and Clinic in Pittsburgh said, "Our results demonstrated that the short sleep-obesity association may be attributed to reduced REM sleep." The report was published in the Archives of General Psychiatry.

Though obesity is linked to burning fewer calories than the body consumes, Liu and his colleagues wanted to identify stages of sleep that they felt could have a link to obesity. They studied 335 children and teens in the age group of 7-17 for three consecutive nights. They monitored their sleep through polysomnography, which measures sleep cycles and stages by recording brain waves, electrical activity of muscles, eye movement, breathing rate, blood pressure, as well as other variables. They measured the weight and height to calculate body mass index (BMI) and found that 45 participants or 13.4% were overweight, while 49 or 14.6 % were at risk for becoming overweight.

They examined total sleep time, time spent in REM, that is usually associated with dreaming, and time it took to fall asleep. They discovered that the children who were overweight slept 22 minutes less per night as compared to the children with normal weight. They also had less REM sleep, reduced eye activity during REM sleep and a longer waiting before their first REM sleep period. The researchers said after adjusting factors such as the children’s demographics, psychiatric diagnoses and other factors they found that one hour less of total sleep doubled the chances of being overweight while one hour less of REM sleep tripled the chances.

"Although the precise mechanisms are currently under investigation, the association between short sleep duration and overweight may be attributed to the interaction of behavioral and biological changes as a result of sleep deprivation," Liu and colleagues reported.

The reason sleep plays an important role is that sleep loss can change hormone levels which in turn may affect hunger. The person also has more time to eat in and this also results in the person feeling sleepy and lethargic during the day, which would make them less inclined to exercise.

An earlier study conducted by the US Centers for Disease Control and Prevention found that people who slept less than six hours or more than the nine recommended each night are at a higher risk of obesity, physical inactivity, smoking and alcohol drinking.  33% of the individuals who slept under six hours were overweight, as were 26% of those who overslept. The lowest rate, 22%, was seen in normal sleepers.

Obesity rate among children aged 6-11 years have more than tripled in the past 30 years, and about 17 % of U.S. adolescents are now overweight or obese. The World Health Organization has classified 400 million people to be obese around the world and obesity is one of the main health problems is the world today.  Researchers feel parents should ensure their children get adequate sleep and improve their sleep environment if needed.