Kids who watch a lot of TV are more likely to be obese, according to several studies—but it's not actually clear how watching TV makes you fat. Do the aliens who run the magic TV rays send subliminal messages telling kids to go lick the butter dish? Or, perhaps a little more plausibly, do children who watch a lot of TV persuade their parents to buy the unhealthy food from the commercials, do they avoid exercise—or do kids eat while they watch TV? To check that last hypothesis, Stanford researchers asked a bunch of kids what they did while they ate.

What the researchers wanted to know: What do children eat while they watch the tube?

What they did: Two groups of Northern California children—one group of ethnically diverse third-graders and one group of mostly Mexican-American fifth-graders—were involved in the study. Dietitians sat the kids down, once in person then on two other days by the phone, and asked everything they'd eaten for the last 24 hours and what they were doing while they were eating each meal or snack. Kids' heights and weight were also measured, to calculate their body mass index, or BMI, a measure of obesity. Ninety-one kids in the third-graders' group and 129 kids in the fifth-graders' group got through three food interviews.

What they found: Most of the kids sometimes ate in front of the TV. On weekends, seven kids ate all of their food while watching TV. On the weekends, kids consumed more than a quarter of their total daily energy while watching television. On weekdays, between 15 and 20 percent of total daily energy was consumed while watching TV. Foods the kids ate in front of the TV weren't any fattier or higher-calorie than foods they ate with the television off. But they were less likely to eat vegetables when watching television than at other times of the day - which makes sense, if the kids were choosing their own TV snacks. Also, in the third-grade, ethnically diverse sample, kids who ate high-fat foods while they watched TV on weekdays were more likely to be overweight.

What the study means to you: Kids certainly seem to be eating a lot while they watch TV. So parents may want to limit how much time their children spend in front of the TV or at least control what kids are eating while they are in front of the tube.

Caveats: Kids had to remember what they'd eaten and what they were doing for the last 24 hours. Also, there were too few kids to be able to measure differences in sex and ethnicity, which can be huge.

Find out more: The study was carried out by researchers at the Stanford Prevention Research Center. Guess how the folks at www.turnoffyourtv.com feel about TV.

Read the article: Matheson, D.M., Killen, J.D., Wang, Y., Varady, A., and T.N. Robinson. "Children's Food Consumption During Television Viewing." American Journal of Clinical Nutrition. June 2004, Vol. 79, pp. 1088-1094.

Free abstract online: http://www.ajcn.org