CHICAGO (AP) -- Junk food remains plentiful at the nation's elementary schools despite widespread efforts to curb childhood obesity, a new study suggests.
Between 2006 and 2010, nearly half of public and private schools surveyed sold sweet or salty snack foods in vending machines or other places, the study found.
There was little change over the four years, a surprising finding given vocal advocacy campaigns to improve kids' diets, said researcher Lindsey Turner, a health psychologist at the University of Illinois at Chicago and the study's lead author.
The study focused on snacks not sold during mealtimes, which until recently weren't subject to government nutrition standards.
Schools most likely to sell chips, cookies or similar foods were in the South, where obesity rates are the highest; these foods were scarcest at schools in the West.
The results are concerning, Turner said, because they show that many schools have not heeded messages from health advocates including the Institute of Medicine, which in a 2007 report urged limiting availability of food in schools outside of mealtimes, and said these items should not be sugary, salty or fatty snack foods.
Many schools in the study also offered more healthy foods outside of mealtimes, including fruit and vegetables. But selling them along with junk food may tempt kids to skip the healthy options, and sends "mixed messages about healthful nutrition," Dr. Thomas Robinson, a Stanford University pediatrician and obesity prevention researcher.
Robinson called the study results "sobering" and said a key strategy for reversing childhood obesity includes improving nutrition in schools.
Recent data suggest that almost 20 percent of elementary school children nationwide are obese. Policies that limit junk food sold in schools have been linked with less obesity among students, said C. Tracy Orleans, a senior scientist at the Robert Wood Johnson Foundation, which paid for the study.
The study appears in Archives of Pediatrics & Adolescent Medicine, released Monday. Robinson wrote an accompanying editorial.
Anti-obesity advocates also have pushed to remove sugary sodas from schools, and some states and schools have enacted bans. Also, a 2010 report found a big decline in sales of these drinks to schools during some of the years studied.
The new study, which focused only on foods, is based on surveys mailed to principals at public and private elementary schools. Nearly 4,000 responded, or more than half of those contacted. The participating schools were nationally representative and there were no geographic or economic differences in schools that didn't respond that would affect the results, Turner said.
Overall, about 45 percent of schools sold sugary and salty snacks. Some schools sold low-fat salty snacks and baked goods, including pretzels and low-fat ice cream, but their high sugar or salt content makes them a poor choice, Turner said.
Candy, salty snacks and regular-fat baked goods were more common at private schools than public schools; and low-fat ice cream was more common at both types of schools than full-fat ice cream snacks.
The study authors say their results should encourage the U.S. Department of Agriculture to crack down on junk food in schools. A law enacted in December 2010, after the study ended, gives the agency authority to do so, and it is developing changes.
Before that measure, USDA policy restricted schools from selling foods "of minimal nutritional value" during mealtimes. Under the new law, the agency can set nutrition standards for all foods sold in U.S. schools.
Another USDA change announced last month focuses on making school lunches healthier, with changes including less sodium and more whole grains.
The changes affecting snack foods "need to be comprehensive, they need to be strong, they need to be specific," and they could be "a game-changer," said Orleans.
A website for the USDA's Food and Nutrition Service says restricting these foods can pose challenges for schools, because many rely on sales of snack foods to boost revenue. But it also explains why changes are needed.
"The constant availability of foods and beverages may increase the likelihood of impulse buying and contribute to overeating by some students," the USDA website says.
It lists states and school districts that have imposed some restrictions on these foods.
Robert Wood Johnson: http://bit.ly/ytMLqM