Trying to shrink the growing waistlines of children, lawmakers want to expel soda, candy bars, chips and other junk food from the nation's schools.

Dangerous weight is on the rise in kids. This week, the federal Centers for Disease Control and Prevention said the rate of obese and overweight kids has climbed to 18 percent of boys and 16 percent of girls. Four years ago, the number was 14 percent.

Lawmakers blame high-fat, high-sugar snacks that compete with nutritious meals in schools.

"Junk food sales in schools are out of control," Sen. Tom Harkin, D-Iowa, senior Democrat on the Senate Agriculture, Nutrition and Forestry Committee, said Thursday. "It undercuts our investment in school meal programs and steers kids toward a future of obesity and diet-related disease."

Harkin and a bipartisan group of lawmakers introduced a bill to have the Agriculture Department set new nutritional standards for all food sold in schools. The goal is to restrict junk food sales in schools.

The department sets standards for breakfasts and lunches in federal school meal programs, which reimburse public and nonprofit private schools for giving free or reduced-price meals to kids. Those meals must follow federal dietary guidelines, which call for more fruits, vegetables and whole grains and less calories, fat, added sugars and sodium.

But the standards don't apply to a la carte lines in cafeterias, vending machines or school stores. The Agriculture Department has tried to restrict junk food before, but a 1983 federal court ruling, in a lawsuit by the National Soft Drink Association, said the limits could only apply to cafeterias during meals, not for the entire day throughout campus.

Today, candy, soda and other snacks are sold in nine out of 10 schools, according to the Government Accountability Office. Already plentiful in high schools, junk food has become more available in middle schools over the past five years, GAO found.

States have tried to limit junk food in recent years. According to the Center for Science in the Public Interest, an advocacy group, legislators in 40 states introduced 200 bills last year to improve nutrition in school foods.

Parents are responsible for how kids eat, but kids are at school for much of the day, said Margo G. Wootan, the center's director of nutrition policy.

"When parents send their kids to school with lunch money, they shouldn't have to worry that the money will be spent on Flaming Cheetos and a Coke instead of on a balanced meal," Wootan said.

The Agriculture Department encourages schools to sell nutritious food, department spokeswoman Jean Daniel said. Daniel declined to comment on the bill, which officials have not reviewed.

She pointed out that schools are supposed to have "wellness policies" that include nutrition guidelines for food in place by July, as required by Congress in 2004.

"More and more children are overweight and obese," Daniel said. "What we do know is we've got to engage parents, teachers, schools, community leaders, organizations — all of us are going to have to work together."

The food industry argues that all foods can fit into a healthful diets.

"My fear is that the criteria will be so restrictive that kids won't be able to optimally learn, in the school environment, about making healthful food choices over time," said Robert Earl, senior director of nutrition policy at the Food Products Association, an industry group.

Earl asked whether more attention should be paid to physical activity in schools.

"Putting all the attention on food alone doesn't necessarily improve inactivity in kids," he said.