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 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…

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…

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.

…Dr. Daniel Taber said…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…

Dr. Taber realizes that school-based rules are limited. Students consume about 25 percent of their calories at school. Looking for a magic switch to turn off won’t change the whole problem. The battle for healthy kids is going to require strategies that take the message home.

But, changing the landscape in school – ceded to the junk food trade years ago – is a healthy step forward. These are verifiable results.