Parents, it could be time to pull your kids away from Saturday morning cartoons and Barney reruns. A study out today in the International Journal of Obesity found that children who spent more time in front of the television tended to be fatter than kids who spent less time glued to the tube.

Researchers recruited children born in 1972 and 1973 in New Zealand. They first saw the children when they were 3 years old, then followed them every two years until the children turned 15. Between the ages of 5 and 11, the children's parents were asked about how much time their children watched TV; at ages 13 and 15 the kids themselves were asked. Researchers also measured the children's height and weight at each visit.

Children watched an average of 2.3 hours of television a week, and those who watched more were more likely to be overweight than those who watched less. Indeed, the researchers found that TV time was a stronger predictor of childhood obesity than either diet or exercise. The researchers weren't sure why TV viewing time predicts children's weight so well, though they say that it is likely related to both their diet and activity-level habits. Previous studies have suggested that there may be a link, and this study adds considerable weight to this claim.

Curiously, the association seems to be stronger for girls than for boys. The researchers are uncertain why that was. They suggest that perhaps it has something to do with the different body types or lifestyle variations. The researchers also say that, at the time of this study, New Zealand had only two free television channels. Now, with more free channels, hundreds of cable stations, and movies-on-demand, there's even more to tempt today's kids into what could be unhealthy TV time.