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Five years after California started cracking down on junk food in school cafeterias, a new report shows that high school students there consume fewer calories and less fat and sugar at school than students in other states.

The findings suggest that state policies can be successful to some extent in influencing the eating habits of teenagers. The study found that California high school students consumed on average nearly 160 calories fewer per day than students in other states, the equivalent of cutting out a small bag of potato chips. That difference came largely from reduced calorie consumption at school, and there was no evidence that students were compensating for their limited access to junk food at school by eating more at home.

While a hundred calories here or there may not sound like much, childhood obesity rates have more than tripled in the United States in the last four decades, and many researchers say that most children and adolescents could avoid significant long-term weight gain by cutting out just 100 to 200 extra calories a day.

“I would definitely say that 158 calories is significant,” said Daniel R. Taber, an author of the study and a postdoctoral research associate at the University of Illinois at Chicago. “When you combine this study with other studies on California law, the body of evidence suggests the schools in California really have made healthier changes by getting rid of things like sweets and candy bars.”

California is one of several states that have sought to reduce childhood obesity by targeting junk food in schools. A decade ago it became the first state to ban the sale of soft drinks in grade schools, and it later enacted a similar ban in high schools. Since 2007, the state has also enforced nutrition standards for “competitive foods” in schools, the snacks and foods that are not included in meal plans but that students can get on school grounds — from vending machines, for example. California law limits the amount of fat, sugar and calories that can be found in these foods.

To study the effect of this policy, the researchers examined data from the Centers for Disease Control and Prevention on the eating habits of high school students in California, comparing it with data on students from 14 states that did not have nutrition standards for vending machine snacks and other foods sold outside of school lunches and other meal plans. Over all, 680 students were included in the study, which was financed by the Robert Wood Johnson Foundation and published in Archives of Pediatrics & Adolescent Medicine.

California students had the lowest daily intake of calories, fat and, especially, added sugars. And it seemed clear that their eating behaviors at school played a large role. California students got a lower proportion of their daily calories from school foods than students in other states: about 21.5 percent, compared with 28.4 percent among students elsewhere.

The reductions in fat, sugar and calorie consumption among Hispanic students “are particularly encouraging given the high prevalence of youth obesity among Hispanic individuals in California and the United States over all,” the authors wrote. “It is also encouraging in light of research that documented the high presence of convenience stores, mobile food vendors and other food outlets surrounding schools in Hispanic communities.”

Still, California’s students had not suddenly become health nuts. They were still eating junk food — just slightly less of it than their peers in other states. And their vitamin and mineral intake was similar to that of students in other parts of the country.

“Students may not be buying as many candy bars at school, but that doesn’t mean that they’re necessarily eating salads instead,” Dr. Taber said, noting that schools still offer items like baked chips and desserts that comply with the regulations but offer little in the way of nutrition.

He said that schools could take an additional step by replacing some of the junk food being filtered out with healthy options like fruits, vegetables and whole grains. Iowa, for example, began requiring in 2010 that at least half of the foods available outside meal plans contain whole grains. Other than that, no state has laws that require whole, unprocessed or fresh foods to be available outside of school lunches for high school students.

School initiatives could also focus on students’ eating behaviors at home, Dr. Taber said.

“We have to recognize that school-based laws have a limited scope because students only consume about 25 percent of their calories at school,” he said. “No one sector or environment is going to be the magical cure. Obesity is a very complex problem with many answers, so we really need to target different aspects of students’ environments.”