March 3, 2014 at 4:06 PM ET
It may not make parents popular, but tossing out the TVs that sit in the corner of most children's bedrooms may keep them from packing on pounds.
A study released Monday in JAMA Pediatrics found that 60 percent of children ages 10-14 had TVs in their bedrooms, and those kids gained about one extra pound per year compared to peers who did not — even once the researchers accounted for time spent watching TV.
Dartmouth University researchers collected data from 3,055 children ages 10-14 and their parents, who were taking part in an ongoing survey of American adolescents. After gathering information from telephone interviews in 2003, and then again two and four years later, the researchers found that children who had a TV in the bedroom gained about an extra pound per year, and kept gaining weight all four years.
Though they could not say a TV in the bedroom "causes" weight gain and obesity, the researchers found the effect held even after they controlled for many other factors including socioeconomic status, parenting styles, education levels and total TV viewing time.
There could be several explanations for the connection. For example, last year, a Finnish study found that media presence (like TVs and computers) in a child's bedroom "predicted significantly shorter sleep duration and later bedtimes." Less sleep is a well-known trigger of weight gain.
It's also possible that a TV in the bedroom leads to more sedentary behavior, more exposure to high-calorie food ads and more snacking.
Whatever the connection, TVs in childhood bedrooms are a significant national issue, said lead researcher Diane Gilbert-Diamond of the Department of Community and Family Medicine at the Geisel School of Medicine at Dartmouth. If 60 percent of children have a TV in their rooms nationally, she said, "this obesity risk factor accounts for over 15 million pounds of excess weight gain per year among U.S. adolescents."
Previous studies have found that 40 percent of children have a TV in their bedroom by age 5 1/2, and that heavy kindergartners are more likely to be obese by eighth grade.
Gilbert-Diamond's study asked about TVs, but in the new screen age, the results may translate to tablets, phones and laptops, too.
Past studies have shown that adults with computers and TVs in their bedrooms also suffer from poor sleep habits and, possibly, a reduced sex life — another good argument for keeping adult bedrooms screen-free as well.