MONDAY, Feb. 6 (HealthDay News) -- Despite efforts to serve healthier meals to school children, roughly half of U.S. elementary school kids can buy junk food at school, a new study finds.

Researchers from the University of Illinois at Chicago said cookies, cakes and chips are still sold through school vending machines, cafeterias and snack bars even if they are not served at lunch.

"Kids can get junk food at school," said Lindsey Turner, a health psychologist and research scientist at the university's Institute for Health Research and Policy. "Despite increasing attention to food in schools and childhood obesity, over time there was no change in the availability of food in competitive venues in schools," she said.

"Competitive" foods and beverages are those sold separately from school lunches.

In 2007, the Institute of Medicine said school meal programs should be the primary source of food at school and recommended limiting access to competitive foods and drinks. If competitive foods were available, they should include fruits, vegetables, whole grains and low-fat dairy products, the Institute said.

"Given these recommendations for what are considered healthy practices in schools, a lot of schools are not following them," Turner said. "Where these products are available, kids are consuming more calories and that is a risk factor for obesity," she added.

Nearly 20 percent of elementary school students included in a 2007-2008 national survey were obese, the study authors said. Because children spend much of their day at school, the experts said efforts to promote healthy eating must include schools.

Increasing awareness of the problem helps, but Turner pointed out that without regulation a lot of schools won't change their policies. "We have a huge window of opportunity now with the United States Department of Agriculture now studying regulations for these foods in schools," she added. Under the Healthy, Hunger-Free Kids Act of 2010, the USDA can set standards for all foods sold in schools.

The report was published in the February issue of the Archives of Pediatrics & Adolescent Medicine.

For the study, Turner and her colleague, Frank Chaloupka, a professor of economics, collected data on nearly 3,000 public and more than 1,200 private schools. They looked at data from 2006-2007 through 2009-2010.

The researchers found that low-fat foods and sweets were more available in larger public schools than in smaller schools.

Children in suburban schools had more opportunities to buy salty, sugary or low-fat foods than children in city schools. In suburban schools, about 53 percent of the children could buy food in one or more places, compared with 44 percent of children in city schools, 41 percent in small-town schools and more than 54 percent in rural schools.

Snacks were more available in private schools than in public schools, especially salty snacks such as chips, the researchers found.

Children living in the South, which has the nation's highest rate of childhood obesity, generally had more places to buy salty and sweet snacks than kids elsewhere. But in public schools in the South, children also had more access to healthier snacks than kids in the Midwest and the West, the researchers found.

That distinction didn't surprise Samantha Heller, a dietitian and clinical nutrition coordinator at the Center for Cancer Care at Griffin Hospital in Derby, Conn.

"Put an elementary school kid in front of a vending machine. He can choose either a candy bar or apple, French fries or a salad. Which do you think he'll go for?" she asked.

"You don't need to be a rocket scientist to know the answer. Children will choose the food that they believe tastes best and is the most fun," she said.

Research has shown that when foods high in salt, sugar or fat are visible and convenient, people will eat them, she explained. "Pair that with marketing that makes these foods cool and exciting, and the results are obvious," she added.

Children will adapt to healthier foods when they are more readily available and have little or no competition from fast or junk foods, Heller said.

More information

For more information on healthful eating for kids, visit the Nemours Foundation.