A cafeteria worker serves salads at Glen Forest Elementary School in Falls Church, Va.  (Jahi Chikwendiu/Washington Post)

In schools where trained chefs jazzed up fare, children ate more fruits and vegetables--and the schools themselves saved money, according to a study released online Monday in the journal JAMA Pediatrics.

Getting them to drink plain milk instead of chocolate milk was a much bigger challenge, however.

Researchers at Harvard University's T.H. Chan School of Public Health studied the eating habits of more than 2,600 third- through eighth-graders in two low-income urban school districts. The vast majority of the children were Hispanic, and their average age was 11 1/2. Trained chefs were randomly assigned to some schools to spice up fruits, vegetables and entrees with low-fat, low-salt recipes. In some of the schools, the project also experimented with how the foods were presented to the children in the food line.

The researchers weighed the quantities of food the kids took and their "plate waste," the food left over when they were finished eating. (Monitors collected the food before children tossed it into the trash.)

Not surprisingly, when kids were offered sauteed broccoli in garlic and olive oil or vegetable soup instead of hideous piles of indistinguishable greens, they tended to eat more of the healthful food, said Juliana Cohen, a research associate in the school's nutrition department.

"What this study is showing is that this is an effective method to reduce plate waste," she said in an interview. Children "are going to like the foods and they're going to eat the foods."

[Why do we still eat this way?]

This is no small matter, because, as the study points out, 30 million children receive meals at school each day and many of them rely on those meals for as much as half their calories. When those calories come in the form of junk food, they contribute to the current condition of U.S. school-aged children, nearly a third of whom are overweight or obese, according to an editorial that accompanies the study.

"When choosing what to eat, children are particularly influenced by the environment in which food is presented," the editorial notes. " 'Choice architecture' is the application of behavioral economic principles to the design of environments in which decisions are made."

The Obama administration, in particular first lady Michelle Obama, has made more healthful school lunches a priority, but this study was conducted before new standards went into effect. (A separate study by Cohen and others belied accounts that kids were rejecting more nutritious food because of its taste.)

[First lady vows again to fight delays in enforcing school lunch standards]

In the current study, researchers found that consumption of entrees didn't change much, but that didn't bother them, because chefs were substituting low fat, low salt and whole grain meals for less healthful alternatives. After three months, the children didn't change their selection of fruits and vegetables prepared by chefs very much, but after seven months they did. They also chose more fruit in schools where it was presented prominently. When both approaches were tried, fruit and vegetable consumption improved.

"We didn't see the increase in consumption immediately," Cohen said. "Schools shouldn't abandon healthy foods if students don't instantly" take to it, she added.

The only failure of the experiment occurred when the researchers pushed plain milk by making it more obviously available, in an attempt to persuade children to choose it over chocolate milk. That just didn't work, and Cohen said schools might have to consider removing the sugar-sweetened beverage from cafeterias if they want children to make that change.

When I asked her how any school district could afford a chef, Cohen said the move actually saved money for the ones in this study. In addition to their training in recipes and food presentation, chefs from restaurants and caterers brought their knowledge of more efficient use of food and inventory control to the school meal operation, trimming costs for the districts.