Kindergartners and first-graders who watched as little as one hour of television a day were more likely to be overweight or obese compared to children who watched TV for less than 60 minutes each day, according to a new study.

Kindergartners and first-graders who watched as little as one hour of television a day were more likely to be overweight or obese compared to children who watched TV for less than 60 minutes each day, according to a study to be presented Sunday, April 26 at the Pediatric Academic Societies (PAS) annual meeting in San Diego.

Efforts to fight the childhood obesity epidemic have focused on getting kids to be more active. Previous studies have shown that children who watch a lot of TV are at risk for being overweight. However, studies have not looked specifically at the link between TV watching and obesity among kindergartners.

For this study, researchers analyzed data from the Early Childhood Longitudinal Survey of 11,113 children who were in kindergarten during the 2011-2012 school year. As part of the study by the National Center for Education Statistics, lifestyle factors that could affect a child's educational performance were collected from parents, including the number of hours of television children watched on weekdays and weekends, and how often they used computers. In addition, children's weight and height were measured.

A year later, 10,853 of the children's height and weight were measured, and parents again were asked about their child's TV habits.

Results showed that US kindergartners watched an average of 3.3 hours of TV a day. Both kindergartners and first-graders who watched one to two hours or more than two hours daily had significantly higher body mass indexes than those who watched less than 30 minutes or 30-60 minutes a day, even after adjusting for socioeconomic status, race/ethnicity and computer use.

In both kindergarten and first grade, children viewing as little as one hour of TV daily were 50-60 percent more likely to be overweight and 58 percent to 73 percent more likely to be obese compared to those watching less than an hour. Computer use, however, was not associated with higher weight.

Furthermore, children who watched one hour or more of TV daily were 39 percent more likely to become overweight and 86 percent more likely to become obese between kindergarten and first grade.

"Given overwhelming evidence connecting the amount of time TV viewing and unhealthy weight, pediatricians and parents should attempt to restrict childhood TV viewing," said study author Mark D. DeBoer, MD, MSc, MCR, associate professor of pediatrics, Division of Pediatric Endocrinology, University of Virginia.

The American Academy of Pediatrics (AAP) recommends limiting children and teens to less than two hours of screen time each day. Dr. DeBoer, however, said even that might be too much.

"Given the data presented in this study, the AAP may wish to lower its recommended TV viewing allowances," he said.