ALEXANDRIA, Virginia (AP) ― The first major nutritional overhaul of school meals in more than 15 years means most offerings ― including the always popular pizza ― will come with less sodium, more whole grains and a wider selection of fruits and vegetables on the side.

First lady Michelle Obama and Agriculture Secretary Tom Vilsack announced the new guidelines during a visit Wednesday with elementary students. Mrs. Obama, also joined by celebrity chef Rachael Ray, said youngsters will learn better if they don’t have growling stomachs at school.

“As parents, we try to prepare decent meals, limit how much junk food our kids eat, and ensure they have a reasonably balanced diet,” Mrs. Obama said. “And when we’re putting in all that effort the last thing we want is for our hard work to be undone each day in the school cafeteria.”

After the announcement, the three went through the line with students and ate turkey tacos with brown rice, black bean and corn salad and fruit - all Ray’s recipes ― with the children in the Parklawn Elementary lunchroom.

Under the new rules, pizza won’t disappear from lunch lines, but will be made with healthier ingredients. Entire meals will have calorie caps for the first time and most trans fats will be banned. Sodium will gradually decrease over a 10 year period. Milk will have to be low in fat and flavored milks will have to be nonfat.

Despite the improvements, the new rules aren’t as aggressive as the Obama administration had hoped. Congress last year blocked the Agriculture Department from making some of the desired changes, including limiting french fries and pizzas.

A bill passed in November would require the department to allow tomato paste on pizzas to be counted as a vegetable, as it is now. The initial draft of the department’s guidelines, released a year ago, would have prevented that. Congress also blocked the department from limiting servings of potatoes to two servings a week. The final rules have incorporated those directions from Congress.

Among those who had sought the changes were potato growers and food companies that produce frozen pizzas for schools. Conservatives in Congress called the guidelines an overreach and said the government shouldn’t tell children what to eat. School districts also objected to some of the requirements, saying they go too far and would cost too much.

The guidelines apply to lunches subsidized by the federal government. A child nutrition bill signed by President Barack Obama in 2010 will help school districts pay for some of the increased costs. Some of the changes will take place as soon as this September; others will be phased in over time.

While many schools are improving meals already, others still serve children meals high in fat, salt and calories. The guidelines are designed to combat childhood obesity and are based on 2009 recommendations by the Institute of Medicine, the health arm of the National Academy of Sciences.

Vilsack said food companies are reformulating many of the foods they sell to schools in anticipation of the changes.

“The food industry is already responding,” he said. “This is a movement that has started, it’s gaining momentum.”

Diane Pratt-Heavner of the School Nutrition Association, which represents school lunch workers, said that many schools won’t count pizza as a vegetable even though they can. Students qualifying for subsidized meals must have a certain number of vegetables and other nutritious foods on their lunch trays.

“Most schools are serving fruit or vegetables next to their pizza and some schools are even allowing unlimited servings of fruit or vegetables,” Pratt-Heavner said.

Celebrity chef Ray said she thinks too much has been made of the availability of pizza and French fries. The new rules will make kids’ lunch plates much more nutrient dense, she said.

“The overall picture is really good,” she said. “This is a big deal.”

The subsidized meals that would fall under the guidelines are served as free and low-cost meals to low-income children and long have been subject to government nutrition standards. The 2010 law will extend, for the first time, nutrition standards to other foods sold in schools that aren’t subsidized by the federal government. That includes “a la carte” foods on the lunch line and snacks in vending machines.

Those standards, while expected to be similar, will be written separately and have not yet been proposed by the department.