Lifestyle prescriptions - you should eat a balanced diet - are notoriously difficult to stick with. But these limits were impossible to avoid.
"Instead of selling candy for a fund-raiser, they were selling carnations. And those are the sort of things that made it holistic across the environment," said Wayne Grasela, senior vice president for food services in the Philadelphia School District, where six middle schools took part in the three-year national program.
The plan was to intervene early, before diabetes develops - and at a young enough age to learn new habits that could prevent or reduce obesity, a major risk factor for the disease. Numerous physicians helped craft the program, but all the action took place in the schools.
"They are already there. They already take physical education and they already eat lunch in the school," explained Barbara Linder, who oversaw the study for the National Institutes of Health.
So researchers set about changing the school.
In gym, for example, "instead of doing layups, with most kids standing in line, we had things set up so balls were being passed back and forth while they waited," said Gary D. Foster, director of Temple University's Center for Obesity Research and Education, who chaired the national study.
Dumbbells, jump ropes, and medicine balls were distributed to groups, with rotations every 45 to 90 seconds to keep everyone moving. Pop music was played so that gyms were seen as "fun places to be with cool things to do," Foster said.
In the cafeteria, the standard pizza was replaced with the same manufacturer's whole-grain, lower-fat version. That shaved nearly 100 calories per slice and the kids didn't notice, said Amy Virus, a registered dietician at Temple who coordinated the study's nutrition component.
Nothing but water - not even 100 percent fruit juice - was stocked in vending machines. "Did they miss the juice? Sure, in the beginning," Virus said, "but they got used to it. And they were buying the water."
Supporting the effort were posters in classrooms (kids dancing, kids eating fruit), decals sent home over Christmas (TAKE THE FAMILY TV TURNOFF CHALLENGE!) and postcards in summer ("Be active for 60 minutes every day."), even a healthy version of Jeopardy!, with 25 cards in English and Spanish.
An estimated 24 million Americans have diabetes, a chief cause of kidney failure, limb amputations, blindness, heart disease, and stroke. Although type 1 diabetes is caused by an auto-immune disorder, type 2 - more than 90 percent of the cases - is often linked to lifestyle factors that lead to weight gain and a gradual loss of the ability to control blood sugar.
Once rare before adulthood, type 2 diabetes has been rising steadily in children. Blacks and Hispanics are at particularly high risk; the government now projects that half of all babies born in those minority groups will develop diabetes later in life.
The new program was designed by researchers at seven major universities and targeted schools that enrolled high percentages of poor and minority students.
They began the interventions in 21 schools - three in each city - in the fall of 2006, when the students were in sixth grade; another 21 schools were designated as controls. A total of 4,603 students completed the study in June 2009, at the end of eighth grade.
Analysis showed that there were significantly greater reductions in several diabetes risk factors - body-mass index scores, average insulin levels, and the percentage of students with the largest waists - at the intervention schools vs. the controls.
All those differences were more pronounced among the 50 percent of students who were overweight or obese to begin with. Within that group, the interventions were associated with 21 percent lower odds of being obese at the end of eighth grade, the researchers reported.
The results were published last week online in the New England Journal of Medicine.
There was one big surprise: Over the study's three years, the number of students who were overweight and obese combined dropped by about the same 4 percent in both the intervention and the control schools.
Some previous research had found a recent flattening of childhood obesity rates that began rising steadily 30 years ago. And the drop may have masked the effects of the interventions.
The most likely reason for the wider weight reversal, researchers said, is that a growing awareness of the problem - now the signature campaign of First Lady Michelle Obama - may finally be altering attitudes and actions of all kinds.
"It is a little bit like tobacco," said Nicolas Stettler, an associate professor of pediatrics and epidemiology at Children's Hospital of Philadelphia who was not connected to the study.
Stettler said the good news on weight should not be interpreted to mean that studies like this one are unnecessary.
"Even though diabetes is leveling off or decreasing, we still have a problem," he said, and research is needed to find the best lines of attack.
In the middle of the study, in fact, Philadelphia school officials were so impressed with one change - replacing all french fries with baked versions - that they expanded it to all city schools.
But they said other changes would be harder to adopt. Serving only whole grain pizza, muffins, hoagie rolls, and other bread products would simply be too expensive.
The national study, which was funded mainly by the NIH, cost $65 million, although much of the cost was to develop the changes and measure their impact.
Kelly D. Brownell, director of the Rudd Center for Food Policy and Obesity at Yale University, praised the study for determining the most cost-effective approaches.
"I couldn't imagine that the country would ever find the will or the money to do something like this on a large scale," Brownell said.
Brownell, who was not involved with the research, favors far-reaching changes that cost little to implement, such as taxing sodas to limit consumption, a proposal that recently failed in Philadelphia City Council.
Temple's Foster, the study chair, said "the next step would be: How can an intervention like this be translated in a less-costly fashion and less-intensive fashion?"
Jeff Brown, a phys-ed teacher in Philadelphia for 31 years who was assigned to work with Temple during the study, isn't waiting. Armed with a state grant, he began making many of the same changes at Baldi Middle School in the Northeast - not one of the study sites - when he returned to teaching last fall.
Of all the study's accomplishments, Brown said, he is most proud of this: "Our most obese students did the best."
"There was a girl," he recalled, who was extremely large, and, like many other obese children, was too intimidated or afraid to participate in regular gym class.
"I called her Hero," Brown said, "because of her commitment and willingness to participate, and because of the change in her affect and attitude: her alertness, her brightness, her happiness."
And because, by the end of the eighth grade, after learning that she could actually do gym, he said, "she was willing to engage in regular conversation, and smile.
"She wasn't before," he said. "I will never forget her."
Highlights of Schools Study
The National Institutes of Health-funded research, called "The HEALTHY Study," has four key interventions.
Change school meal programs, snack bars, vending machines, fund-raisers, and classroom parties, to:
Lower average fat content of food served in school.
Provide at least two fruit/vegetable servings in lunch programs and one at breakfast.
Limit all desserts and snacks to 200 calories or less.
Eliminate milk greater than 1 percent fat, all drinks with added sugar, and nearly all 100 percent fruit juice.
Provide at least two servings of grain-based foods or legumes, with at least 2 grams of fiber per serving, in lunch programs, and one serving at breakfast.
Increase physical activity levels in gym, by:
Providing at least 225 minutes of physical education class over every two-week period.
Ensuring 150 minutes of moderate-to-vigorous activity (at least 130 heartbeats per minute) over two weeks.
Using strategies in gym class to better manage administrative time, reduce inactivity, and increase activity through motivational techniques, equipment, exercises, and games.
Support the nutrition and phys-ed goals, through:
Classroom instruction on related topics.
Self-learning materials for students during breaks.
Newsletters to families with recipes and support tips.
Promote all the above, with:
Posters (some on this page) in English and Spanish.
Public address announcements.
Creative messaging, such as a Jeopardy! game.
Study details, videos of phys-ed class and an interview with the research chair, Gary D. Foster of Temple University:
Contact staff writer Don Sapatkin at 215-854-2617 or firstname.lastname@example.org.