About 70 percent of youngsters have a TV in the bedroom, and one-third are overweight or obese, the researchers said.

Previous studies have found a link between bedroom TVs and increased risk of being overweight in children, but these studies have primarily used body mass index (a ratio of height to weight), which is not an exact measurement of body fat.

Watching TV in the bedroom may pose extra hazards compared with regular TV viewing. Studies have linked bedroom TVs with reduced amounts of sleep, a factor that itself has been linked to weight gain, said study researcher Amanda Staiano, of the Pennington Biomedical Research Center in Baton Rouge, La.