How Oppenheimer’s double-martini and cigarette diet challenged Cillian Murphy

Maybe it was Cillian Murphy’s way of truly inhabiting the character of J. Robert Oppenheimer that he found himself developing the scientist’s lack of appetite for food, with the actor losing enough weight to embody Oppenheimer’s famously slender frame, which, at times, was viewed as unhealthy.

In Christopher Nolan’s “Oppenheimer,” the Manhattan Project director appears to survive on Chesterfield cigarettes and double martinis, as Murphy said in an interview with The Guardian. In a couple scenes in the movie, the UC Berkeley physicist is seen grudgingly accepting a slice of an orange from his good friend, the future Nobel Prize-winning physicist Isidor Rabi.

As explained in “American Prometheus,” the biography on which the film is based, the 5-foot-10 Oppenheimer wasn’t a big eater — sometimes to his detriment. After he was recruited to lead efforts to build the atomic bomb, he took the Army physical, with the idea that all scientists working at the Los Alamos laboratory would become commissioned Army officers. The idea was eventually abandoned, while Oppenheimer failed the physical because of his low weight. He was only 128 pounds — 27 pounds under the idea weight for a man of his age and height.

Questions about Murphy’s weight loss for the role began circulating after Emily Blunt, who plays Oppenheimer’s wife, Kitty, made a passing comment during an ExtraTV interview about how “emaciated” the actor became for the role. She said the already slender Murphy tried to stay focused on the “monumental undertaking” of playing the brilliant and conflicted theoretical physicist and “could only eat, like, an almond every day.” In the context of the interview, alongside co-star Matt Damon, Blunt’s comment sounds a bit tossed off, as if it’s a gross exaggeration of the extent to which Murphy limited his intake of food.

For his part, Murphy has avoided saying too much about his diet for “Oppenheimer,” and he hasn’t divulged how many pounds he lost. He doesn’t want the focus of his performance to be on “Cillian lost x weight for the part,” as he told The Guardian. Certainly, the physical transformation that stars undergo for roles often becomes a main talking point — the pounds Robert De Niro packed on for “Raging Bull,” the weight Tom Hanks lost for “Philadelphia” and “Cast Away” and the ups and downs of Christian Bale’s size as he’s moved from movie to movie.

Murphy acknowledged to The Guardian that he was determined to embody Oppenheimer’s silhouette and tested himself to see how little he could eat. “You become competitive with yourself a little bit which is not healthy. I don’t advise it,” he said. But in preparing for the role and turning up on set each day to play the man, Murphy said he began to forget about eating food, in the same way he forgot about sleep.

“It’s like you’re on this (expletive) train that’s just bombing. It’s bang, bang, bang, bang,” Murphy told The Guardian. “You sleep for a few hours, get up, bang it again. 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 …”

Murphy quickly searched for words, then said, “But it was good because the character was like that. He never ate,” but he smoked constantly and drank plenty of martinis, with the rims dipped in lime, as the film shows.

Oppenheimer’s physical and mental health were tested during the intense, two years he spent working on the bomb, according to “American Prometheus.” His weight dropped to 115 pounds, “skin-and-bones” for a man of his height,” the book said. “His energy level never flagged, but he seemed to be literally disappearing little by little, day after day,” the book said.

As far back as his childhood, Oppenheimer was known for looking as though he “wasn’t getting enough to eat or drink,” according to a classmate of from the progressive Ethical Cultural School that he attended while growing up on New York’s Upper West Side, the book reported. That appearance was associated with his early social awkwardness  — which he would definitely outgrow as an adult. His classmates said he always looked “preoccupied with whatever he was doing or thinking” — as if he didn’t really have time to even think about eating.

As Oppenheimer emerged from a painful adolescence and suicidal despair in his early 20s, he developed into gregarious and charismatic young academic. As a star of UC Berkeley’s Physics Department in the 1930s, he liked to go out to restaurants around the East Bay and San Francisco, as “American Prometheus” explained. Perhaps, though, he was less interested himself in savoring different cuisines, but he certainly liked to pick up the tab as he treated his less well-off colleagues and graduate students to meals.

In his later years, Oppenheimer and his family liked spending several months each year on the island of St. John in the Virgin Islands. There, Kitty Oppenheimr did her best to serve up meals of seafood salad, octopus and barbecued shrimp. While that all sounds healthy and appetizing — the Oppenheimers getting their protein directly harvested from the sea — Kitty wasn’t known to be the best cook. One Christmas dinner, the couple served their guests little more than champagne and Japanese seaweed, and Oppenheimer ate practically nothing. “My God,” Doris Jadan, their friend and island neighbor, recalled, “if the man ate a thousand calories a day it was a miracle.”

When The Guardian interviewed Murphy, the Irish actor appeared to have gained back the weight he lost, as he acknowledged it wasn’t healthy to continue to eat as little as Oppenheimer. The “Father of the Atomic Bomb” only lived another 22 years after the creation of the first weapon of mass destruction. He was diagnosed with lung cancer in February 1966 and died the following year at age 62.