U.S. military-age youth are increasingly unfit to serve — mostly because they’re in such lousy shape. According to the latest Pentagon figures, a full 35 percent, or more than one-third, of the roughly 31.2 million Americans aged 17 to 24 are unqualified for military service because of physical and medical issues. And, said Curt Gilroy, the Pentagon’s director of accessions, “the major component of this is obesity. We have an obesity crisis in the country. There’s no question about it.”The Pentagon draws its data from the Centers for Disease Control, which regularly tracks obesity. The steadily rising trend is not good news for military recruiters, despite their recent successes, nor for the overall health of the U.S. population.Put another way, only 4.7 million of the 31.2 million 17- to 24-year-olds in a 2007 survey are eligible to enlist, according to a periodic survey commissioned by the Pentagon. This group includes those who have scored in the top four categories on the Armed Forces Qualification Test, or AQFT; eligible college graduates; and qualified college students.