Matt Damon Gets Toned for 'Green Zone'

He packed on the pounds for "The Informant!" -- now Matt Damon is telling "Extra" about getting fit for his new action flick, "Green Zone."

In the new movie (opening March 12), Damon plays a US Army officer forced to go rogue as he hunts for weapons of mass destruction in the Middle East.

See photos of Matt and the 2010 Oscar nominees

At the NYC premiere of "Green Zone," "Extra's" AJ Calloway told Damon he was looking trim, and he responded, "I'm chasing three little kids around, man!" Damon is a stepfather to wife Luciana Bozán Barroso's daughter Alexia, and they have two daughters together, Isabella and Gia.

See photos of celebrities and their kids

The star says he was inspired by the troops overseas to get back in shape. "When these guys go off to fight, they really get in shape and they don't know what it's going to come down to," he explains. "They're very serious about it."

The Oscar winner also admits that working on "Green Zone" gave him a newfound respect for the men and women who serve. He says, "When you see the guys, you stop and just say 'Thank you.' They're pretty great."