Mindless snacking in front of the television set may start long before children know how to work the remote control, a U.S. study suggests.
In an experiment with 60 kids aged 2 to 5 years, researchers focused on how advertising influences what's known as eating in the absence of hunger.
They gave all the children a healthy snack to make sure they had a full belly, and then sat the kids down to watch a TV program with ads for Bugles corn chips or for a department store.
All of the kids had Bugles corn chips and one other snack in front of them while they watched the show. Children who saw ads for the corn chips ate 127 calories on average, compared to just 97 calories for kids who didn't see Bugles on the screen, researchers report in Pediatrics.
"This is the first study to show that exposure to food ads cues immediate eating among younger children - even after they had a filling snack," said lead study author Jennifer Emond of Geisel School of Medicine at Dartmouth College in Hanover, New Hampshire.
"Young children average up to three hours of TV viewing a day," Emond added by email. "If kids are exposed to food ads during that time, they may unconsciously overconsume snacks which can lead to extra weight gain."
More than one third of U.S. children are overweight or obese, according to the Centers for Disease Control and Prevention.
The American Academy of Pediatrics (AAP) recommends against any screen time for children younger than 18 months and suggests no more than an hour a day for kids aged 2 to 5 in part to encourage language development, support healthy sleep habits and limit sedentary activity that can set preschoolers on a path toward obesity.
The type of TV program matters too. The AAP encourages educational programming like "Sesame Street" that can support language learning.
For the experiment, researchers sat kids down to watch a 14-minute segment of "Elmo's World" that included three minutes of advertising.
Before the show started, all of the kids could snack as much as they liked on banana, sliced cheese and crackers. They also got water to drink.
Children were randomly assigned to view ads for national department stores or to watch Bugles spots that showed kids playing and eating the corn chips.
While the shows played, kids were given bowls of Nabisco Teddy Grahams and Bugles corn snacks.
There wasn't a meaningful association between how much kids ate during the program and their age, weight or the way their parents typically supervised mealtime at home.
In particular, researchers looked at whether parental feeding restrictions - which can include things like pressuring kids to eat or prohibiting certain foods - and didn't find any association between these practices and the amount of snacks kids consumed in the experiment.
One limitation of the experiment is that it included mostly white, affluent rural kids, which may make the results less relevant to the broader population of U.S. children, the authors note.
Young children can also be unreliable when they tell adults whether they are full, so it's possible some children who claimed they had enough to eat before watching TV were actually hungry, the researchers also point out.
Even so, the findings should give parents another reason to limit children's exposure to media that comes with advertising, said Dr. Julie Lumeng, a researcher at the University of Michigan's C.S. Mott Children's Hospital who wasn't involved in the study.
"Many children's programs are now instead using product placement to advertise," Lumeng added by email. "Parents should also pay attention to how product placement occurs in the television programs or other media their young children may be watching."
Age 2 may be too young to understand how ads can influence behavior, Lumeng noted.
"But parents can consider gradually introducing the power of advertising to young children as a trategy for helping their children resist the effects of these ads," Lumeng said. "Ultimately limiting the child's exposure to the ads is the key strategy."