July 1 (HealthDay News) -- Watching food ads on TV leads to a boost in snacking among children and adults, increasing the risk of weight gain, U.S. researchers say.

Yale University researchers conducted a series of experiments to test the effects of food commercials on television. One test found that children aged 7 to 11 who watched a half-hour cartoon that included food commercials ate 45 percent more snack food while watching the show than children who watched the same cartoon with non-food commercials.

That increased amount of snacking would lead to a weight gain of nearly 10 pounds a year, unless it was countered by decreased intake of other foods or increased physical activity, the researchers said.

In another experiment, adults who saw TV ads for unhealthy foods ate much more than those who saw ads that featured messages about good nutrition or healthy food.

"This research shows a direct and powerful link between television food advertising and calories consumed by adults and children," lead author Jennifer Harris, director of marketing initiatives at the Rudd Center for Food Policy and Obesity at Yale, said in a news release from the university.

"Food advertising triggers automatic eating, regardless of hunger, and is a significant contributor to the obesity epidemic. Reducing unhealthy food advertising to children is critical," she said.

The study appears in the July issue of the journal Health Psychology.

SOURCE: Yale University, news release, July 1, 2009