America's expanding waistlines might pose a threat to national security, the Pentagon says.

More than a quarter of Americans ages 17-24 are too overweight to serve, depleting the eligible pool of potential soldiers. The number of men deemed ineligible to serve based on weight has doubled in the last 50 years; among women, the number has tripled.

Those currently serving aren't immune to weight issues, with 1 in 20 members of the armed service suffering from weight problems, up from 1 in 50 just seven years ago. Weight issues can lead to multiple health issues that can literally leave servicemen and women unfit for battle.

"It's not just a major health issue for our nation; it's also become a national security issue," retired Rear Adm. James Barnett said.

Besides shrinking the number of qualified candidates for military service, weight issues are requiring the Pentagon to spend more than $1 billion a year on medical care related to weight and obesity--a steep price tag as the government faces a mounting national debt.

In February, first lady Michelle Obama teamed up with the military to promote sweeping changes being made the nutrition standards for troops, as well as what military dining facilities serve.

Nutrition education will also become part of basic training for the Army.