WASHINGTON -- As schools turn to vending machines to ease budget gaps, a health advocacy group wants them to fill the machines with healthier choices.

The Center for Science in the Public Interest says school vending machines are usually filled with fatty foods and sodas -- which add to the child obesity problem. The U.S. government says 13 percent of children are overweight.

The group says better snacks include applesauce, bottled water, raisins and granola bars.

Margo Wootan, CSPI's nutrition policy director, said schools that have made the switch prove it's not true that kids will only eat junk -- they just need to be offered healthier choices.

Health advocates want Congress to increase government oversight of foods sold outside the lunch line. In the meantime, the CSPI says each community can set its own nutritional standards.

On Monday, the organization released its School Foods Tool Kit -- a manual for parents and school officials who want to improve school foods.

Unlike the foods in vending machines, school lunches have actually been improving over the last 10 years, the CSPI said. Their fat, cholesterol, and sodium have decreased, while fruits and vegetables have become more plentiful.

"Kids who buy a school lunch are at least getting a good balance of nutrients, whereas kids spending their lunch money in the vending machine might get Doritos and a Coke," Wootan said.

The organization urges parents to visit their child's school at lunchtime to see firsthand whether the food offered is healthy.

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