We owe it to the children who aren't reaching their potential because they're not getting the nutrition they need during the day, she wrote in the Monday edition of the Washington Post.

And we owe it to our country -- because our prosperity depends on the health and vitality of the next generation.

The Child Nutrition Bill would allocate $4.5 billion over a decade to support school cafeterias and introduce new standards for food sold in schools, including in vending machines.

The legislation, if passed, would effectively allow the Agriculture Department to ban junk food in schools.

Tackling childhood obesity has become Michelle Obama's signature issue as she spearheads a national campaign with a 70-point plan, challenging Americans to defeat the problem in a generation.

Obesity is one of the biggest health challenges facing the United States. The U.S. Centers for Disease Control and Prevention says two-thirds of American adults and 15 percent of children are overweight or obese -- a condition putting them at risk of developing heart disease, diabetes and cancer.

In some states, the childhood obesity rate is above 30 percent.

Disease related to excess weight costs the United States about $150 billion each year in direct medical costs. About $17 billion of government dollars now go toward child nutrition, mostly school lunches.