Bradley Cooper‘s buff bod is all natural.
To bulk up for American Sniper, the Oscar-nominated actor – who struggled with addiction a decade ago – didn’t use any stimulants.
“I did it naturally because I’ve been sober for 10 years and didn’t want to do anything,” he tells Vanity Fair in its January issue.
As the film’s writer-producer Jason Hall previously told PEOPLE, the star “had a strict, crazy diet” and hit the gym with a personal trainer.
But getting in shape sans steroids to play real-life Navy SEAL sniper Chris Kyle was easier said than done.
“I had a realistic conversation,” Cooper, 39, says in the VF cover story. “Can I do this in three months naturally? Can I gain 30 pounds of f—ing muscle? I didn’t know if I would be able to do it or not. Thank God – luckily – my f—ing body reacted fast.”
Cooper also discussed how finding the right roles drives his career.
“I always knew I wanted to be in the trenches with a director making the movie, he says. I always felt that’s what I m supposed to be doing. I always knew deep down that if I’m not going to do that then I’m not too long for this business.”
He found that with American Sniper, which adapts Kyle’s autobiography and chronicles his courage in Iraq and later struggles to adapt back to civilian life at home.
In VF, Cooper recalls getting the chance to visit Kyle’s house with director Clint Eastwood, meeting his wife and children.
“I knew this was sacred ground that I was on and it was a very special gift that Clint and I got to be there in this house and meet these people,” he says. “It wasn’t lost on us.”
American Sniper opens in theaters Dec. 25.