Elementary school children appear to down many of their daily calories while planted in front of the television, a new study shows.

TV viewing has caught a good part of the blame for the growing problem of excess weight and obesity among U.S. children. Some research has linked TV time to the risk of obesity, and experts have speculated that one reason is that children tend to eat a lot while watching television.

The new study of third- and fifth-graders at California public schools found that, on average, children ate roughly 20 percent of their daily calories while watching TV. The weekend was a particularly popular time for munching in front the tube, as kids consumed more than one-quarter of their calories for the day during TV time.

The findings, published in the American Journal of Clinical Nutrition, are the first to give an idea of how much TV-time munching is actually going on, according to lead study author Dr. Donna M. Matheson, a research associate at Stanford University School of Medicine.

“Children are eating a lot of food in front of the TV,” she told Reuters Health, “and parents should be aware of it.”

However, Matheson said, there are still a lot of unknowns - including whether the children would have been eating less if the TV were off, and whether those who most often combined TV and food face a greater risk of becoming overweight.

For the study, Matheson and her colleagues surveyed an ethnically diverse sample of third- and fifth-graders on three separate occasions, asking them what they’d eaten over the past day and what they were doing while they ate.

Overall, the children ate 17 to 18 percent of their weekday calories, and about one-fourth of their calories on a weekend day, while watching TV. In general, they ate fewer fruits and vegetables, and less soda and fast food, when the TV was on.

The amount of food the children ate during TV time was not associated with their body mass index, or BMI, a measure of their weight in relation to their height. However, among third-graders, those who ate higher-fat foods in front of the TV had a higher BMI than those who ate lower-fat fare.

If a parent is worried about a child’s weight, Matheson said, turning off the television may be a good first step. And when it’s on, she added, parents can try giving kids healthy snacks such as fruits and vegetables.

SOURCE: American Journal of Clinical Nutrition, June 2004.