During a recent interview with Vanity Fair, actor Bradley Cooper revealed his decision to bulk up naturally for his role as U.S. NAVY SEAL, Chris Kyle in the upcoming film, "American Sniper."

Cooper revealed that though he had only three months to prepare physically for the role, he refused to take steroids or partake in any unnatural methods to gain muscle due to his past struggles with drug addiction.

"I did it naturally because I've been sober for 10 years and didn't want to do anything," he explained.

"I had a realistic conversation. '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," he added.

In addition to undergoing a strict workout regimen and diet to prepare for his "American Sniper" role, Cooper revealed that his past struggles dealing with his father, Charles' death also helped him prepare for the upcoming film, Us Weekly reports.

"Losing someone close to me [helped me prepare]," Cooper explained. "Going through love and loss...knowing what's important. Realizing that the bottom line is that all I got is me, so it's about time to stop trying to be something that I think you would want me to be. Or that would give me what I think I need. As you get older, thank God, your body deteriorates, but your soul sort of flourishes."

Now that the Oscar-nominated actor has a series of successful films added to his resume including the Oscar winning, "Sliver Linings Playbook," Cooper is now looking forward to working more behind-the-scenes with future films, he explained.

"I always knew I wanted to be in the trenches with a director making the movie," he said. "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."

"American Sniper" hits theaters on December 25.

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