'American Sniper': How Bradley Cooper Gained 40 Pounds for Role

"We had to force-feed him," his trainer said.

In the latest issue of Men's Health, it's revealed that Cooper packed on 40 pounds for the role, since the man was around 230 pounds in real life.

“I had to get to the point where I believed I was him,” Cooper told the magazine. “At 185 pounds, it would’ve been a joke. His size was such a part of who he was ... “Chris wasn’t ripped. He wasn’t sinewy. He was just a bear.”

Cooper's trainer Jason Walsh helped the man pack on the pounds over a 10-week period.

The pair trained two times a day, beginning at 5 a.m., doing deadlifts and squats.

Cooper, 40, had to eat more than 5,000 calories a day and "We had to force-feed him," Walsh said.

Cooper added, “It was a real shock to my body. If it’s pizza and cake, that’s one thing. Putting 6,000 calories a day in your body gets old quick.”

In addition to five meals a day, Cooper ate energy bars and workout drinks.

“His body just absorbed everything I threw at it," Walsh continued.

On his new weight, Cooper said, "It changes the way you walk, the way people relate to you. If someone bumps into you on the sidewalk, they kind of ricochet off. You go to a party and everyone’s dancing, you’re not being moved by anybody.”