With over one-third of American children overweight, the search is on to figure out why. Happy Meals get blamed, as do sodas, trans fats and just about everything else.

A new study even blames television - not necessarily how much time is spent watching it, but having it in the bedroom. The paper in JAMA associated a bedroom television with weight gain in children and adolescents, and say it is unrelated to the time they spend watching.

Their evidence: a telephone survey in 2003 of 6,522 boys and girls (ages 10 to 14 years) that asked about bedroom televisions. Body mass index (BMI) at two and four years after baseline was based on self-report and parent-reported weight and height for their children. They found that an estimated 71 percent of children and adolescents (ages 8 to 18 years) have bedroom televisions.

Diane Gilbert-Diamond, Sc.D., of the Geisel School of Medicine at Dartmouth, Lebanon, N.H., and colleagues report that, at baseline,  59.1 percent of the children surveyed reported having a bedroom television.

It's pretty good to be poor in America because more poor and minority kids have bedroom televisions. Boys also have them more than girls. Having a bedroom television was associated with an excess BMI of 0.57 at two years and 0.75 at four years of follow-up, and a BMI gain of 0.24 between years two and four.

The authors speculate the association could possibly be due to disrupted sleep patterns or greater exposure to child-targeted food advertising, although their analysis did not investigate causal reasons.

“This study suggests that removing bedroom televisions may be an important step in our nation’s fight against child obesity. … This work underscores the need for interventional studies to explore whether removing televisions from child bedrooms results in lower adiposity (fat) gain," they wrote.

Citation: JAMA Pediatrics March 3, 2014,  doi:10.1001/jamapediatrics.2013.3921