Cillian Murphy Was ‘Competitive’ with Himself About ‘Oppenheimer’ Weight Loss: ‘I Don’t Advise It’

Cillian Murphy slimmed down to play the tormented father of the atomic bomb, J. Robert Oppenheimer, in Christopher Nolan’s upcoming period piece.

Murphy, who skipped out on the ensemble cast’s dinners according to co-star Emily Blunt, revealed to The Guardian that he sometimes forgot to eat entirely.

“It’s like you’re on this fucking train that’s just bombing. It’s bang, bang, bang, bang. You sleep for a few hours, get up, bang it again,” Murphy said of his marathon performance. “I was running on crazy energy; I went over a threshold to where I was not worrying about food or anything. I was so in it, a state of hyper something. But it was good because the character was like that. He never ate.”

Murphy noted that the real-life Oppenheimer survived off “cigarettes and pipes, he would alternate between the two,” before dying of cancer in 1967. To play the scientist for “Oppenheimer,” Murphy was determined to appear as similar to the real-life person as possible, complete with a “porkpie hat and the pipe.”

“You become competitive with yourself a little bit which is not healthy,” Murphy said. “I don’t advise it.”

Without revealing how much he shed for the role, Murphy added, “I don’t want it to be, ‘Cillian lost x weight for the part.'”

The “Batman Begins” alum said in an earlier New York Times interview, “I love acting with my body, and Oppenheimer had a very distinct physicality and silhouette, which I wanted to get right. I had to lose quite a bit of weight, and we worked with the costume and tailoring; he was very slim, almost emaciated, existed on martinis and cigarettes.” He added, “He had these really bright eyes and I wanted to give him this wide-eyed look, so we worked on his silhouette and expressions a lot before starting.”