In a victory for everyone from Jamie Oliver to Michelle Obama, the school cafeterias of America are to redesign their menus around strict calorie limits and minimum quotas of healthy food.
New guidelines unveiled by the US Department of Agriculture this week will require schools to offer pupils more whole grains, less sodium and fat, and twice as many fruits and vegetables as before.
But the changes aren't a complete coup for health advocates. After extensive lobbying of Congress by the junk food industry, pizza can be classified as one of the two "vegetables" that a child must now be offered each day, as it contains tomato paste.
Mrs Obama, who has made tackling childhood obesity her signature issue as First Lady, joined the Agriculture Secretary, Tom Vilsack, at a school in Virgina on Wednesday to unveil the first changes to nutritional guidelines for 15 years.
"When we send our kids to school, we expect that they won't be eating the kind of fatty, salty, sugary foods that we try to keep them from eating at home," she said.
Mrs Obama joined 800 children for lunch. In place of the traditional American fare of hamburgers and hot dogs, they were served turkey tacos, brown rice, and fresh salsa.
Calorie limits will be calculated on a sliding scale, depending on a child's age. Younger pupils will be expected to consume no more than 650 calories at lunchtime.
That figure rises to 700 and then 850 for older teenagers.
The rules apply to all public schools in the nation, and will affect roughly 12 million children.
At present, America is by some distance the fattest nation in the world, with 17 percent of children said to be clinically obese.