March 3 (Bloomberg) -- Limiting the time that young children spend with television and computers shaves calories from their diets and reduces their risk of becoming obese, researchers said.

Investigators attached a $100 electronic device called the TV Allowance to televisions and computers in the homes of 70 volunteer families. The device controls the amount of screen time users have and was programmed to cut the allotment by 10 percent monthly, for several months, for children aged 4 to 7.

Children whose viewing was eventually cut in half ate less, spent less time on sedentary activities and developed a healthier body mass index, a ratio of height to weight. The reduction in screen time didn't translate into additional physical activity, providing insight into how sitting in front of a television or computer contributes to obesity in children, the researchers said.

``It looks like screen time is influencing eating more than physical activity,'' said Leonard Epstein, a professor of pediatrics at the State University of New York at Buffalo. ``It's possible that when there is a regular pairing of eating and watching TV, just watching television becomes a cue for eating,'' he said. ``And television can also be a distraction from how much you are eating.''

The study, funded by the National Institute of Diabetes and Digestive Diseases and the State University of New York at Buffalo, appears in the March edition of Archives of Pediatrics & Adolescent Medicine.

Mindmaster

Children who had a TV Allowance, made by closely held Mindmaster Inc. of Miami, played computer games and watched television almost two hours a day less than those given no restraints, wrote Steven L. Gortmaker, from the Harvard School of Public Health's department of society, human development and health. They also consumed about 150 fewer calories a day, he said in an editorial accompanying the study.

``Food and beverages are heavily advertised on children's television, and television viewing is associated with increased energy intake,'' he wrote. ``This association can occur because of intake while watching television, or, more generally, as a consequence of food marketing.''

The American Academy of Pediatrics recommends no more than two hours of television or computer time each day for children aged two and older, and none for younger children. Previous studies suggest children spend 50 percent or more time than recommended in front of television and computer screens.

``New innovations that assist parents may help makes these recommendations a reality,'' Gortmaker said.

Outgrowing Obesity

In the study, 30 percent of the children in the TV Allowance group who started out overweight grew out of the excess pounds and weren't too heavy after two years, Epstein said. In contrast, just 18 percent who were allowed an unrestricted amount of television and computer time were no longer overweight at the end of the trial.

Randal Levenson, the president of Mindmaster and inventor of the TV Allowance, said he created the device in 1991 as a way to control the amount of time his kids spent in front of the television. It worked, he said, and now thousands of the devices are sold each year across the country.

``Grades go up and kids get fitter if you reduce TV time,'' he said. ``I'm not anti-television, I'm anti-too much TV.''

The device also builds negotiating skills, he said. Girls often sell their minutes to their brothers, or the children combine their viewing time to maximize their allowance, he said.

While parents can monitor and restrict the amount of television their children watch without the TV Allowance or similar products, the devices take some of the conflict out of the process, Epstein said.

``When the device controls the children's television watching, there isn't a daily battle or a daily fight,'' he said. ``In the process, the child has to learn to allocate their time better.''

To contact the reporter on this story: Michelle Fay Cortez in Minneapolis at mcortez@bloomberg.net

Last Updated: March 3, 2008 16:32 EST