The guide also limits kids to only one cup of starchy vegetables a week. That means schools could not offer French fries every day.
The guidelines apply for the most part to lunches subsidized by the federal government. These meals are served as free and low-cost meals to low-income children and long have been subject to government nutrition standards.
The new law for the first time extends nutrition standards to other foods sold in schools that aren't subsidized by the federal government, including "a la carte" foods on the lunch line and snacks in vending machines. Those standards, while expected to be similar, will be written separately.
The changes could take years to implement.
The announcement comes just a few weeks after President Barack Obama signed into law a child nutrition bill that will help schools pay for healthier foods, which often are more expensive.
Some school groups have criticized efforts to make meals healthier, saying it will be hard for already-stretched schools to pay for the new requirements.
New school lunch guidelines would:
- Establish the first calorie limits for school meals.
- Gradually reduce the amount of sodium in the meals over 10 years, with the eventual goal of reducing sodium by more than half.
- Ban most trans fats.
- Require more servings of fruits and vegetables.
- Require all milk served to be low fat or nonfat, and require all flavored milks to be nonfat.
- Incrementally increase the amount of whole grains required, eventually requiring most grains to be whole grains.
- Improve school breakfasts by requiring schools to serve a grain and a protein, instead of one or the other.
The new guidelines are based on recommendations by the National Academy of Sciences. Many school districts, including the Los Angeles Unified School District, have already taken steps to serve healthier meals.
Later in January, the USDA is also planning to release new dietary guidelines for the general public which include reducing the amount of sodium and increasing the amount of fruits, vegetables and whole grains in the American public's diet.
The Associated Press contributed to this report.