‘Oppenheimer’ Star Cillian Murphy Took On an Insane “One Almond Every Day” Diet to Become His “Almost Emaciated” Character

In order to embody the leading role of J. Robert Oppenheimer, the creator of the atomic bomb in Christopher Nolan’s Oppenheimer, Cillian Murphy barely ate throughout the entirety of filming.

Murphy’s co-star Emily Blunt, who plays his wife Kitty Oppenheimer in the movie, described Murphy’s role as “such a monumental undertaking,” telling Extra that “he could only eat, like, an almond every day” and “was so emaciated.”

Murphy confessed to The Guardian that after taking on this diet, he sometimes forgot to eat or even sleep, explaining that he “was running on crazy energy.”

“I went over a threshold to where I was not worrying about food or anything,” he shared. “I was so in it, a state of hyper …hyper something. But it was good because the character was like that. He never ate.”

While Murphy admitted that he doesn’t “advise” anyone else take up the diet, he found himself becoming “competitive with [himself] a little bit,” testing his limits in order to embody Openheimer’s “emaciated” figure.

The script for the film, which Murphy noted to The New York Times “was written through the first person,” entailed a hyper-focus on his character, his appearance and mannerisms.

“I love acting with my body, and Oppenheimer had a very distinct physicality and silhouette, which I wanted to get right,” he told the outlet.

Blunt isn’t his only co-star to weigh in on the star’s drastic diet. Matt Damon told People that “of course [Murphy] didn’t want to come and have dinner with [him and Blunt],” as “his brain was just too full.”

The diet turned out to be just one aspect of the measures taken by Murphy and Nolan in order to correctly capture Oppenheimer’s persona. In his interview with The Guardian, Murphy noted “walking on the balls of his feet,” using “a vocal tic,” and spending “a long time on hair” to transform him into Oppenheimer, whom he described as “dancing between the raindrops morally.”

“He was complex, contradictory, polymathic; incredibly attractive intellectually and charismatic, but… ultimately unknowable,” he said.

You can watch Oppenheimer in theaters on Friday (July 21).