Bradley Cooper Bradley Cooper

Bradley Cooper has put on a whopping 40 pounds — but there's a reason!

The American Hustle star has gained the extra weight for an upcoming film in which he'll play Navy SEAL Chris Kyle, E! News reports.

See celebrities who have had a dramatic weight loss

"He put on like 40 pounds," said Nashville star Eric Close, who will co-star alongside the Oscar-nominated actor in American Sniper. "He's really been working hard. He looks great. He's really taken on this character. ... He really takes this story personally and wants to do an honorable job for Chris' memory and his family."

American Sniper is based on Kyle's book, American Sniper: The Autobiography of the Most Lethal Sniper in U.S. Military History.

Cooper will next lend his voice to the upcoming superhero film Guardians of the Galaxy, which hits theaters this summer.

What do you think of Cooper's weight gain?