New Delhi, Dec 03 (ANI): Bradley Cooper has revealed that he "naturally" bulked up for his role of Navy SEAL sniper Chris Kyle in Clint Eastwood's upcoming ' American Sniper .' Bradley, who could use a little help for bulking up from stimulants or he could do it the old fashioned way by working out excessively and eating right, said that he chose the latter, a web portal reported. He added that he did it naturally because he has been sober for 10 years and didn't want to do anything.