At the same time, children today are less likely to grab a fresh apple or any vegetable at all at snack time. The trend toward more fruit juice and less fruit and vegetables is a dangerous one because fresh produce contains fiber and lots of valuable nutrients that children need to stay healthy, Popkin said.

Consumption of desserts declined from 1977 to 2006. However, children today still snack on cake, cookies and other rich foods, and such desserts still account for a significant source of calories, Popkin noted.

An increase in calories, especially from unhealthy snack foods, plus an inactive lifestyle that includes lots of TV and computer screen time can lead to weight gain and even obesity, he said.

"Kids are eating nearly three snacks a day and that's too much," Popkin said, adding that parents should:

try to limit snack time to once a day for children six and older.make sure they stock up on plenty of healthy snack food items like apple slices, carrots and other fruits and vegetables. limit a young child's consumption of junk food or candy and talk to older teens about the importance of a healthy diet, including snacks.But the solution to the junk food problem might require broader action, Popkin noted. For example, he said, schools should eliminate junk food sold in school vending machines or on the cafeteria line, and lawmakers might need to step in and regulate or restrict advertising that sells unhealthy foods to children, a practice that has been shown to increase snacking behavior.

healthaffairs/