Brianna Santo Domingo, left, and Isabella Fernandz eat salads during lunch at Sunset Park Elementary School in Miami, Florida, in 2012. The salad bar was introduced at the school to promote healthy eating habits.

MIAMI — Around him, many kids in the Sunset Park Elementary cafeteria in South Miami-Dade, Fla., were gingerly nibbling at fresh vegetables from the new salad bar, encouraged by hovering parent volunteers and teachers. Manuel Rodriguez, 6, had his eyes on something else.

A plastic container, brought from home, contained a thick square of chocolate cake with a layer of white frosting. As he dug into the cake, he was asked if that was all he had for lunch. He shook his head somberly, pointing to a Pedialyte nutrition drink.

With one in three American children considered overweight or obese — and the trend dangerously upward — the federal government has launched a new campaign this school year to strengthen nutritional requirements for school lunches.

The move has been strongly championed by the White House, particularly first lady Michelle Obama, and it has sparked a backlash. In the politicization of nutrition, Republican stalwart Sarah Palin has defiantly served cookies to children. Conservative talk show host Rush Limbaugh blames the Obamas for destroying Twinkies, while the National Association to Advance Fat Acceptance persuaded Disney World to close down an anti-obesity exhibit.

In the case of school laws, the new standards emphasize fresh fruits and vegetables, whole grains and low-fat milk while limiting caloric intake.

The response, like a serving of succotash, has been mixed.

Many students were dismayed, at least initially. A poll taken by the Coral Gables High newspaper last fall found that 59 percent didn’t like the new regulations. Editor Ali Stack said that "students are now used to the food," but miss Papa John’s pizza. Overall, she said, attitudes about cafeteria offerings had not changed: "Gross" before and "gross" now.

Sabrina Rodriguez, editor of the Hialeah High newspaper, said most students "still did not like the new standards." They got used to it, she said, but most still throw out the vegetables.

Penny Parham, nutrition director for Miami-Dade schools, said the tales of more waste aren’t supported by reports from field offices. In fact, she said increased numbers of elementary and middle school kids are eating cafeteria lunches this year, while high school participation remains about the same. Broward schools also report no waste increase.

The larger question is how much a school — or any institution outside the home — can alter eating patterns that many experts believe are deeply ingrained, starting from the earliest years. Many obesity experts believe changing those habits will take decades. "Note that it took 50 years of anti-tobacco campaigns to lower smoking rates from 50 percent of the population to 20 percent," said James Hill, director of the Center for Human Nutrition in Colorado.

"There’s no question that schools can’t fix everything," said Roland Sturm, a senior economist specializing in obesity issues at the California-based RAND Corp. Parents’ influence remains "hugely important," he said, but "the school environment is an important norm-setter for healthy behavior."

With most public school kids in Miami-Dade on free or reduced-lunch programs, and many also eating breakfast, the influence of school menu changes may be bigger than in many places. Still, Sheah Rarback, a University of Miami nutrition expert, said improving student diets will require "a combined effort to tackle this devastating problem, a real partnership between home and school."

The Obama administration has campaigned to reduce the nation’s fat, which has been growing at an alarming rate. The percentage of kids aged 6-11 who are obese has more than doubled in the past three decades, according to the Centers for Disease Control and Prevention. Obese adolescents aged 12-19 have more than tripled. Extra pounds mean extra health problems, such as diabetes and heart disease, adding expense to an industry that already swallows 20 percent of the American economy.

The Healthy, Hunger-Free Kids Act required schools to limit lunches to no more than 650 calories for elementary kids, 700 for middle schoolers and 850 for high schoolers. Students must be offered a vegetable, a fruit, a low-fat or non-fat milk, a protein and a grain. They must pick at least three, one of which must be a vegetable or a fruit. A student also could satisfy the fruit or veggie requirement by choosing a juice without added sugar.

"We’re not trying to create waste," said Olga Botero, Miami-Dade schools executive director of food and nutrition.

When the standards kicked in last fall, there were a number of reports of students rebelling at being forced to eat vegetables. The New York Times found hundreds of kids in a Wisconsin school boycotting the cafeteria and students in a small town in western Kansas creating a parody video. (In it, athletes keel over in the gym for lack of nourishment and kids stash bags of chips in their lockers to keep from starving.) Even Comedy Central’s "The Daily Show" got into the act, showing a New York school waste can overflowing with vegetables.

South Florida school nutrition experts say objections were more muted here because there wasn’t an overnight switch from junk to healthy foods.

"We’ve been ahead of this," said Parham, Miami-Dade’s nutrition director. "We took off hot dogs last year. It’s been quite a while since we served corn dogs. We started whole wheat toast ahead of the requirements." Deep fryers are gone, and so are vending machine sodas.

Darlene Moppert, manager of Broward, Fla.’s nutrition education, said schools there ditched fryers in the 1990s and have offered fresh fruits — bananas, apples and such — for a decade. "It’s just that now they’re required." She said she’s heard few negative comments.

At Cypress Bay in Weston, Fla., student journalist Nicole Moshe said her school has "a large amount of students who are very health conscious" and love the fresh fruits and vegetables. She did a survey on the school’s food court and found the salad line was as long as those for pizza and hamburgers.

She said "very little" of the fruits and salads are thrown out. "It comes down to the individual student. Those who are more health conscious are going to make healthier sources."

Each county has its own regulations in addition to the federal standards. Broward allows some vendors’ products, like pizza, to be sold in some cafeterias, while Miami-Dade no longer permits outside offerings like pizza because companies can’t promise to meet healthy guidelines. This year, Miami-Dade also eliminated junk food from vending machines — much to some students’ consternation — while Broward still allows some items, like whole grain Pop-Tarts.

"I want my Pop-Tarts!" lamented junior Hadiya Trowell at Alonzo and Tracy Mourning High in North Miami, Fla., as she finished a lunch of brown rice, beef strips and mixed vegetables.

The Mourning vending machines used to be filled with Pop-Tarts and such. Now they’re all fresh food — tuna-salad sandwiches and parfait yogurts.

When a Herald reporter and photographer visited Mourning High, kids were in a rush to get their food and eat it during the 30-minute lunch break. For fruits and vegetables, students could pick from whole apples, a box of celery and carrot sticks, hot mixed vegetables, packaged apple slices, strawberry yogurt and several kinds of juices.

Eating patterns varied widely. At one freshmen table, Aubyn Roche had cleaned her plastic plate, including vegetables, while across from her Ariana Aviles hadn’t touched her vegetables. "I don’t like them," she said flatly.

Roshawn Janvier, a freshman, had chosen a package of apple slices, which remained unopened on his plate after he had finished the rest of the meal. When a reporter asked him if he was going to eat the slices, he said, "Yes!" His buddy Kenneth Gratereaux snorted. "No he’s not." Later, as Janvier left the cafeteria, he said he’d eaten "a little" of the apple slices.

At the end of the first lunch shift, the Mourning waste bins contained some vegetables and rice among the plastic dishes, but not a lot.

Rebecca Landesman, a Mourning student journalist, emailed: "From what I see people who buy school lunch will eat the main part of the meal like the chicken or tacos or rice, but they won’t eat the fruit and vegetables, which doesn’t look as appealing."

But as the school year has gone on, she wrote, "I don’t really hear people complaining about it too much anymore ….When lunch is over there are dozens of trays left on the tables that have some part of the meal that was left uneaten. Cookies are 50 cents each and they’re probably the most purchased food the cafeteria sells."

Teaching nutrition in schools can be a tricky matter. Sturm, the RAND obesity expert, warned that schools can send mixed messages if, for example, they’re "using candy or cookies for reward and running for punishment."

He notes that healthier foods alone won’t produce thinner kids. Giving kids better nutritional options is a good step, he said, but "don’t expect that this magically prevents obesity."

South Florida schools appear to understand that. Miami-Dade has several innovative programs encouraging exercise, even for high school students who don’t take regular physical education classes. There’s also a program with Miami-Dade Parks and Recreation, promoting after-school exercise programs with healthy snacks — an alternative to flopping on the couch at home and snacking on junk foods while watching TV.

While everyone endorses exercise, the value of salad bars remains hotly debated.

Broward schools haven’t used salad bars for the past few years because "it’s tough to control contamination," said Moppert, the nutrition manager. "And we had a lot of waste." Broward now serves salads in clear plastic containers. In Miami-Dade, salad bars are permitted in schools, when there are enough staff members to control the area. said Parham.

This year, Publix and Produce for Kids, a nonprofit group, have donated 17 salad bars to Miami-Dade schools, including Sunset Park Elementary, where the kids point to the items they want behind a sneeze screen and a cafeteria worker spoons the desired items into a bowl.

At the beginning of the school year, "we had hardly any kids" using the salad bar, said Principal Sara Martin. Then she staged a "tasting day" in which each student was given six little paper cups to sample vegetables and fruits they had never tried before. "They tried it and loved it." And they liked that they could control which items went into the salad. About 250 of the school’s 650 students now regularly use the salad bar, Martin said.

"If you start with kindergartners and first graders," said Rarback, the UM nutritionist, "then they’re going to be more familiar with fruits and vegetables by the time they’re in 11th and 12th grades. I think this process is going to evolve over time."