School meals for millions of U.S. children will be healthier under obesity-fighting standards unveiled on Wednesday that double the fruits and vegetables in cafeteria lunches — but won’t pull French fries from the menu. 

In the first major changes to school breakfasts and lunches in more than 15 years, the new U.S. Department of Agriculture guidelines will affect nearly 32 million children who eat at school. They will cost the federal government about $3.2 billion to implement over the next five years.

"Improving the quality of the school meals is a critical step to building a healthy future for our kids," Agriculture Secretary Tom Vilsack said in a statement.

The new meal requirements are part of the Healthy, Hunger-Free Kids Act championed by first lady Michelle Obama. President Barack Obama approved the measure in late 2010.

The guidelines double the amounts of fruits and vegetables in school lunches and boost offerings of whole grain-rich foods. The new standards set maximums for calories and cut sodium and trans fat, a contributor to high-cholesterol levels. 

Schools may offer only fat-free or low-fat milk and must assure that children are getting proper portion sizes, USDA said.

The new standards will be largely phased in over a three-year period, starting in the 2012-13 school year.

About 17 per cent of U.S. children and teenagers are obese, according to the Centers for Disease Control and Prevention.  About one-third of U.S. adults are obese.

Fries with that?

Lawmakers altered the guidelines in November. They barred the USDA from limiting French fries and ensured that pizza counted as a vegetable because of its tomato paste.

Trade associations representing frozen pizza sellers like ConAgra Foods and Schwan Food, as well as French fry sellers McCain Foods and J.R. Simplot, were instrumental in blocking changes to rules affecting those items.

Margo Wootan, nutrition policy director for the non-profit Center For Science in the Public Interest, said that the new standards were a big improvement despite food industry lobbying and the congressional revamp.

"The new school meal standards are one of the most important advances in nutrition in decades," she said in a statement.

The Environmental Working Group said the changes could pack a financial punch since they may help reduce medical bills related to diabetes and other obesity-related chronic diseases.

"A healthier population will save billions of dollars in future health care costs," said Dawn Undurraga, EWG’s staff nutritionist.

As an example of a new meal, the USDA said an elementary school lunch could be whole wheat spaghetti with meat sauce and a whole wheat roll, green beans, broccoli, cauliflower, kiwi, low-fat milk, low-fat ranch dip and soft margarine.

That lunch would replace a meal of a hot dog on a bun with ketchup, canned pears, raw celery and carrots with ranch dressing, and low-fat chocolate milk.

As part of the new standards, schools will receive another six cents a meal. The $3.2 billion needed to implement the program for five years covers the cost of food and increased USDA inspections of school menus.

Food and beverages sold in vending machines and other school sites "will also contribute to a healthy diet," the USDA statement said.

USDA gives school districts funds for meals through its National School Lunch and School Breakfast programs.

— Additional reporting for Reuters by Lisa Baertlein in Los Angeles