Obama, who has led a healthy eating and fitness program for children for two years, lent her voice on Thursday to the military's efforts to overhaul the food it serves.

In an event at Little Rock Air Force Base, Obama announced a new Pentagon obesity and nutritional awareness campaign that will change nutrition standards across the services for the first time in 20 years.

The changes will bring more fruits, vegetables, whole grains and food choices that are lower in fat to 1.45 million troops a day at all 1,100 American military dining facilities in the coming months.

"This isn't just a drop in the bucket - this is really a big splash," Obama said.

"It's happening because our military leaders know it's not just a diet issue, it's not just a health issue. This is truly a national security issue," she said at the base, which already has a pilot program to improve nutritional quality of food available to service members and their families.

Obama cited a recent army study that says more than one quarter of 17- to 24-year-olds are too overweight to serve in the military. Active members of the military are also becoming more overweight, a Pentagon official said, and that causes a "readiness problem."

"The military is always taking the lead in terms of setting standards," said Assistant U.S. Secretary of Defense for Health Affairs Jonathan Woodson. "Now we have an opportunity to take leadership ... as we face this epidemic of obesity."

Woodson said the U.S. military spends about $4.65 billion in food services each year. It also spends an estimated $1.1 billion a year on medical care associated with excess weight and obesity.

To promote good choices, the military will redesign menus and supply healthier foods in mess halls and in vending machines and snack bars on military bases.

The first lady, who has been doing the rounds of television talk shows and late-night comedy shows to promote her "Let's Move" campaign to improve the nation's eating and exercise habits, said changes by the Pentagon would send an important message to the country.

"Simply put, this is America's entire military once again stepping forward to lead by example," she told airmen at the base after touring a dining facility.

Earlier in the day, Obama practiced what she preached as she stood on a stage with Olympic athletes, politicians and celebrity trainers to lead 14,000 arm-pumping Iowa children in an energetic rendition of "The Interlude" - a dance made popular at Northern Iowa University.

(Reporting by Deborah Charles; Editing by Xavier Briand)

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