When I came on to Jack Reacher, I had just taken my girlfriend on vacation and ate everything I could. I put on about 15 pounds, so when I met [the Jack Reacher team] I was clocking in at about 180. They looked at me and were like, "You're just gonna lose five pounds, we're gonna keep you skinny".

The director, Moisés Kaufman, just received the national medal of the arts from President [Barack] Obama . He wrote and directed The Laramie Project and he has directed several Pulitzer prize-winning plays. He's a pretty profound director in the theater.

I was eating with the help of a nutritionist so I was definitely putting in the appropriate calories and vitamins and minerals into my body; however, it was still so little that if I had the tiniest piece of sugar, my brain would go crazy. If I had some alcohol during the run of that play, my brain would go crazy.

You can hear how hard I work, I think, from these stories I'm telling. I'm incredibly dedicated and I'm sort of known as that to a point that people tease me about it.

I read as many books about the psychology of a psychopath as I could and I researched what exactly happens to soldiers.

A sociopath can imitate emotions, where a psychopath really doesn't have that capacity. They can't fool people into thinking anything and they're usually lacking major empathy for anybody besides themselves.

You get a role like this in a big action movie [like Jack Reacher] and you can go one of two ways: you can paint in broad strokes, which happens a lot in action films, or you can get very detailed.