(The Blaze/AP) -- New Agriculture Department guidelines for school lunches will take effect this fall, including the first national calorie and sodium limits for what can be served on lunch lines.
In addition, schools must offer dark green, orange or red vegetables and legumes at least once a week, and students are required to select at least one vegetable or fruit per meal. Flavored milk must be nonfat, and there's a ban on artificial, "artery-clogging" trans fats.
But researchers are still trying to figure out how to enforce the new "guidelines."
"We don't want healthy trash cans. We want kids who are eating this stuff," Kern Halls, a former Disney World restaurant manager who now works in school nutrition at Orange County Public Schools in Florida, summarized.
At a School Nutrition Association conference in Denver this summer, food workers heard tips about how to get children to make healthy food choices in the cafeteria. There, Halls demonstrated some healthy recipes for curious cafeteria managers, while joining White House chef Sam Kass to prepare a veggie wrap using a whole-wheat tortilla.
The first step, cafeteria workers were told at the conference, is to stop thinking of lunchtime as a break from academics, but rather a crucial part of a child's school day.
"Your job is not to serve kids food. Your job is motivate kids to be adventurous and healthy eaters," said Barb Mechura, head of nutrition services at schools in Hopkins, Minn.
Her school district recruited parent volunteers to be elementary-school "food coaches," touring cafeterias and handing out samples of fruits and vegetables. The food coaches would also "demonstrate" eating them.
As the kids graduate to middle and high schools, and adults become less welcome in the cafeteria, schools can tap student ambassadors to be food coaches, perhaps asking the baseball team or a popular student athlete dish out veggies. Or, high school seniors might give underclassmen samples of a new vegetable coming to the cafeteria.
School cafeterias also are using "cutting-edge market research." They're filming what kids eat, test-marketing new products before they go on the line and doing menu surveys to find out exactly what students think about a dish's taste, appearance and temperature.
A Colorado State University professor studied the dining habits of kids in Loveland, Colo., with an eye toward measuring ways to get them to choose healthier foods. Leslie Cunningham-Sabo, who photographed "before" and "after" pictures of kids' lunch trays, found that kids eat more fruits and vegetables if they have lunch after recess, instead of before recess. She found that corn consumption went up when generic "corn" labels were replaced with colorful cards describing the vegetable as "mellow yellow corn."
"Don't put veggies in opaque containers or give them boring labels like 'corn,'" Cunningham-Sabo instructed the lunch workers, showing diagrams of how to lay out a service line to encourage trips to the salad bar.
Another trick — just like supermarkets place impulse buys like candy and chewing gum by the checkout, lunch lines should place easy-to-grab fruits and veggies by their own cash registers. Her study saw cafeterias double their sales of fresh fruit when they placed it colorful bowls in a convenient place.
"You really have to be in their face with what's available," Cunningham-Sabo said.
The marketing doesn't stop at the cafeteria doors. Lassen View Elementary School in Redding, Calif., got children to eat more fruits and vegetables when cafeteria manager Kathie Sardeson started a recess snack cart bringing the foods straight to the playground for kids to munch on.
Her school also bought an iPad 2 to raffle away to students who entered by choosing a healthy breakfast yogurt parfait and turning in tickets attached to the bottom. She tempted kids to try unusual flavors by giving out "Fear Factor Smoothies" including unexpected ingredients such as spinach. Sardeson said schools can be persuaded to invest more in nutrition promotions because the payoff is better students.
"Food is one of the most important influences on your everyday brain cells," Mechura said. Healthy eating habits, she argued, is as important as everything else schools are trying to teach.
"We have to change," Mechura said. "We have to build an environment that creates excitement about what we are doing rather than fear of new foods."
Here are all the guidelines, by grade:
Grades K-5: 8 to 9 servings per week
Grades 6-8: 8 to 10 servings per week
Grades 9-12: 10 to 12 servings per week
Students should have at least one serving of grains each day, and one-half of offerings must be rich in whole grain.
Grades K-5: 8 to 10 ounces per week
Grades 6-8: 9 to 10 ounces per week
Grades 9-12: 10 to 12 ounces per week
Nuts, tofu, cheese and eggs can be substituted for meat in some cases.
Grades K-12: 1 cup per day
Fat-free, low-fat and lactose-free milk options are allowable.
Grades K-8: One-half cup per day
Grades 9-12: One cup per day
Only half of the weekly fruit requirement can come from juice.
Grades K-8: Three-quarters cup per day
Grades 9-12: One cup per day
Weekly requirements for vegetable subgroups, including dark green, red/orange, beans/peas, starchy and others.
By July 2014, sodium levels for lunches should not exceed:
Grades K-5: 640 milligrams
Grades 6-8: 710 milligrams
Grades 9-12: 740 milligrams
A timetable sets targets for further reducing sodium levels by 2022.
No more than 10 percent saturated fats. No trans-fat, except for those naturally occurring in meat and dairy products.
Grades K-5: 550 to 650 per day
Grades 6-8: 600 to 700 per day
Grades 9-12: 750 to 850 per day
Calories can apparently be averaged over the week.