More than one-third of Americans ages 17-24 are unqualified for military service because of physical and medical issues, U.S. military officials said.

Curt Gilroy, the Pentagon's director of accessions, said the United States has "an obesity crisis."

"There's no question about it," Gilroy told the Navy Times. "Kids are just not able to do push-ups, and they can't do pull-ups. And they can't run."

The Pentagon figures -- 35 percent of the roughly 31.2 million Americans ages 17-24 are ineligible for military service -- are drawn from data from the Centers for Disease Control. In a study scheduled to be released Thursday in Washington, U.S. Secretary of Education Arne Duncan and a group of retired military officers say young Americans' lack of overall fitness for military duty is a national security threat, the Navy Times reported.

The report, drawing on Pentagon data, says 75 percent of the nation's 17- to 24-year-olds are ineligible for service for a variety of reasons, including:

-- 35 percent ineligible for medical/physical problems.

-- 18 percent ineligible for illegal drug use.

-- 9 percent ineligible for mental problems.

-- 18 percent have too many dependents.

-- 5 percent have a criminal record.