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Today, for the first time in 15 years, the USDA proposed a major overhaul to nutrition expectations at school cafeterias.

This proposal would establish the first calorie limits for school meals, gradually reduce the amount of sodium therein by roughly half, and ban most trans fats from the school cafeteria. It would also require all milk to be nonfat and demand more servings of fruit and vegetables.

The changes are based on 2009 recommendations by the Institute of Medicine; if adopted, they will affect about 32 million children at government-subsidized school cafeterias nationwide.

This comes at a time when, according to government data, nearly 32 percent of American children of 6 to 19 years old are overweight or obese. These children are more likely to have a number of health problems such as high blood pressure, high cholesterol and type 2 diabetes.

"The United States is facing an obesity epidemic and the crisis of poor diets threatens the future of our children--and our nation," said Tom Vilsack, Agriculture Secretary. He explained: "If we don't contain obesity in this country it's going to eat us alive in terms of health care costs."

Some schools already follow the proposed rules. For example, the Los Angeles Unified School District has independently pursued healthier standards for its meals. In the past few years LAUSD cafeterias have reduced sodium and trans fats as well as sugars and added dyes; they have begun to offer increased servings of whole wheats, fruits and vegetables. Dennis Barrett, director of the LAUSD's Food Services Division, explained: "We are well on our way to meeting most all of the standards."

But, again, the announcement is just a proposal. The USDA will be seeking public input on it until April 13, 2011 (at this website), and when the rule is finalized it will only gradually be made into law. It could be several years before schools nationwide are actually required to make these alterations.

Contact Ryan Lee Kindel here, and follow him on Twitter: @ryanleekindel.