Bradley Cooper gained over 40 pounds for American Sniper

Bradley Cooper, who plays US Navy Seal Chris Kyle in American Sniper, reportedly ate 8000 calories a day to more than 40lbs for the role.

Writer and producer Jason Hall told People Magazine that the 40-year-old actor was eating about every 55 minutes or something like that. Hall continued that Cooper used his own trainer, who was busting on him and he was working out four hours a day for several months.

Hall added that the American actor was determined to do it naturally, he didn't want to use any hormones or steroids or anything. 

American Sniper is based on the book  American Sniper: The Autobiography of the Most Lethal Sniper in U.S. Military History by Chris Kyle. With 255 kills, 160 of which were officially confirmed by the Department of Defense, Kyle is the deadliest marksman in U.S. military history. The film also stars Sienna Miller, Kyle Gallner, Sam Jaegar among others.