More than a third of American youth of military age are unfit for service, mainly because they are too fat or sickly, the Army Times reports, quoting the latest Pentagon figures.

Most of the rest are too dumb or have used too many drugs to qualify, the study shows.

The report says 35% of the 31 million Americans aged 17 to 24 are unqualified because of physical and medical issues.

"The major component of this is obesity," Curt Gilroy, the Pentagon's director of accessions, tells the Times. "We have an obesity crisis in the country. There's no question about it."

He also said young people, by and large, can't do push-ups.

"And they can't do pull-ups," Gilroy says. " And they can't run."

The Times says the Pentagon gets its data from the Centers for Disease Control, which has found that the percentage of youth 18 to 34 who are considered obese has jumped from 6% in 1987 to 23% now.

Here's the Pentagon's breakdown of the ineligible population, according to the Times:

Medical/physical problems, 35%.

Illegal drug use, 18%.

Mental Category V (the lowest 10% of the population), 9%.

Too many dependents under age 18, 6%.

Criminal record, 5%.

Update at 1:06 p.m. ET: The Times reports that Education Secretary Arne Duncan and a group of retired military officers will issue a report on Thursday warning that the situation is so dire it amounts to a threat to national security.

That study will show that when all factors are considered, 75% of military-age youth are not eligible to serve.

(Posted by Doug Stanglin)