Simple kid-friendly training in good nutrition got 8- to 10-year-olds to eat healthier for three years, although snacks, desserts and pizza still make up an astonishing third of the youngsters' diets, researchers reported.

It's the biggest study ever to track the impact of childhood nutrition education, and it backs a major new government campaign that aims to keep preteens from getting fat by using some of the same tactics — through training programs and real-world tips directed at their parents.

"It suggests that kids who learn to eat healthy during their adolescence will continue to eat healthy," said Dr. Elizabeth Nabel, chief of the National Heart, Lung and Blood Institute, which sponsored the research and on Wednesday begins the "We Can!" program to spread the results.

One key: Don't forbid the foods that children find yummy, but teach balance — that there are "go foods" for every day, "slow foods" for a few times a week, and "whoa foods" to eat only once in a while.

For example, eating a healthy breakfast is important for staying fit. Unsweetened whole-grain cereal, like oatmeal, is a go-food choice. Prefer waffles or pancakes? Those are "slow foods," perhaps for the weekend. Croissants, doughnuts or sweetened breakfast cereals are whoa foods, maybe for a holiday or vacation treat.

Getting grade-school children in the habit of drinking lowfat milk instead of whole milk, eating an apple a day, or choosing carrot sticks or raisins as an after-school snack makes them more likely to continue those habits when they're old enough to choose foods on their own, said Northwestern University dietitian Linda Van Horn, who led the new study.

But children must have access to tasty, healthy choices, stressed Van Horn: If only hot dogs are served at the baseball game, that's what they'll eat. Noses turn up when the only choice at the school lunch program is mushy beans.

Already, the nation has 9 million children ages 6 to 16 who are overweight, according to federal health officials. Overweight children usually grow into overweight adults, at increased risk of heart disease, diabetes, asthma and other disorders — not to mention the turmoil of being teased and left out of sports and other fun activities.

The new study tracked 595 children, half of whom had received, with their parents, special education on how to make healthier food choices. Three years later, the kids who had attended the nutrition classes were eating more "go" foods than their peers in every food group except fruit, Van Horn reports in the June issue of the journal Pediatrics. They also ate fewer "whoa" foods with one exception: pizza. And for desserts, they were more likely to pick lower-fat options like frozen yogurt.

Still, neither group ate enough fruits or vegetables, and the high amount of daily snacking and pizza was stunning, said Van Horn.

Now the $2.6 million "We Can!" campaign aims to extend those food lessons — and tips on fitting in more physical activity — to all 8- to 13-year-olds.

It's a two-pronged program. First, more than 35 communities so far have signed up to offer youth and parent education materials, or to offer hands-on activities such as summer camps that teach nutrition and afterschool programs that promise healthy snacks.

Second, a government Web site aimed at parents — http://wecan.nhlbi.nih.gov — provides education on ways to fight obesity, including such tips as:

_Choose food portions no larger than your fist, a growing guide for a growing child. Restaurants almost always serve too much; plan to bring home leftovers.

_Make it easier to get healthy snacks and harder to get unhealthy ones. Don't keep chips in the house, but keep a bowl of fruit within reach on the kitchen counter. Choose a checkout line without the candy display.

_Limit TV or video games to two hours or less a day. Don't just sit and watch — challenge your children to a jumping-jack contest during commercials.

_Go on an after-dinner family walk or bike ride; make outdoor play, or visits to gyms or recreation centers, routine.

Many children live in communities where traffic, distance or crime make outdoor play or getting to a park or gym impossible. Also Wednesday, the National Institutes of Health is bringing together researchers to debate how much a child's environment increases the risk for obesity, and how to help.