ALEXANDRIA, Va. — 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.

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 10 years. 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.