Researchers said they'd hoped that with more encouragement for districts to improve nutrition in foods offered at school and an increasing focus on childhood obesity, fewer kids would have access to unhealthy options -- especially ones that they might substitute for a more balanced school lunch.

Elementary school "is really a crucial period where the preferences and behavioral habits are being developed," said Lindsey Turner, one of the study's authors from the University of Illinois at Chicago.

"If kids are early on in that environment where that junk food is around, then it potentially becomes a habit that's harder to break," she told Reuters Health, adding that the new finding was "disappointing."

The study was based on a survey of school teachers and food service workers about snack options, so the researchers couldn't tell how many children actually bought the sugary and salty snacks, or whether kids who went to schools with vending machines and snack bars were more likely to be overweight than those that didn't.

The survey results, from close to 4,000 schools queried between 2006 and 2010, showed that about half of all public and private elementary schools had vending machines, snack bars or similar options where food was sold during lunchtime. Almost all of them sold sweet or salty snacks, while about two-thirds also had healthier fruit and vegetable options.

Kids generally had more access to junk food in suburban schools and schools in the southern United States, according to findings published Monday in the Archives of Pediatrics & Adolescent Medicine.

Dr. Y. Claire Wang, who studies childhood nutrition and obesity at the Columbia University Mailman School of Public Health in New York, said that some previous studies have suggested that school snacks have become more nutritious in recent years.

But the new findings suggest that "there is a lot to be done still," Wang told Reuters Health.

Wang was not involved in the new study, though both she and the research are supported by the Robert Wood Johnson Foundation.

Turner said that there's currently a "huge window of opportunity," as the United States Department of Agriculture is in the process of deciding on regulations for snacks available in schools, which could limit the amount of fat and sugar in those products.

She said that in the meantime, parents should know what's being sold at their kids' schools, and when.

Wang added that parents can provide a good example of healthy eating and exercise for their young kids, and can also petition schools to offer better snack options.

"The community (and) the parents have to take a lot of responsibility as well," she concluded.

SOURCE: bit.ly/xjdzV1 Archives of Pediatrics & Adolescent Medicine, online February 6, 2012.

• A Permanent Economic Emergency