For his role as former CIA agent Robert Baer in the film "Syriana," George Clooney added 35 pounds to his pretty boy persona and rendered himself nearly unrecognizable.
"I'm sort of happy at the idea that people, when they first see me in the movie or when they first see the poster, don't even know it's me," he told reporters at the time the film came out. "To me, that makes me proud."
But the extra pounds also weighed him down and contributed to the tear in his dura, creating a cranial spinal fluid leak. That threw off his basketball game and his love for motorcycling. "It was depressing," he said.
It paid off in the end. Clooney took home an Oscar for best supporting actor.
Clooney's good buddy Matt Damon lost 40 pounds to play a drug-addicted Gulf War Veteran in "Courage Under Fire." The role nearly ruined his health.
In an interview on "Inside the Actor's Studio," Damon said his weight-loss regimen consisted of a diet of chicken breast, egg whites and one plain baked potato per day and a large amount of coffee and cigarettes. He also ran six and half miles in the morning and at night.
After the film wrapped, he said on the Oprah Winfrey Show, he had to be under medical supervision for several months for damage done to his adrenal glands.
At the beginning of "Raging Bull," De Niro, who also won an Oscar for his performance, is lean and mean as boxing champion Jake La Motta. By the movie's end, he's nearly unrecognizable as the washed-up boxer.
Production on the film was done in two parts. Most of it, including all the boxing scenes, was shot first. Then production halted for several months while the king of method acting, De Niro, gained 60 pounds, reportedly by eating Italian food.
Director Martin Scorsese has said in interviews the scenes of fat Jake were shot quickly with few takes because of the physical strain on De Niro.
To portray a skinhead in the movie "American History X," Norton put on 35 pounds of muscle on his normally slender frame.
He has said he upped his protein intake to gain muscle. In an interview with Total Film, he said he spent about two and a half months getting into shape because he felt the character called for it.
"I think he's a character who's armored himself against the pain he's experienced in his life with his rage," he said. "I wanted him to have physically manifested that sort of armoring as well. When you talk to those kids, that's what those tattoos and muscles are all about. In a lot of ways, it's about creating a shield or a psychic empowerment device to deal with the feeling of being marginal and insecure."
The statuesque former model reportedly added 30 pounds to her 5-foot-9 frame by eating Krispy Kreme donuts and potato chips to play her Oscar-winning role as serial killer Aileen Wuornos in the film "Monster."
Even though the real Wuornos was much shorter than Theron, she had a toughness that Theron wanted to convey. With the additional pounds, makeup and prosthetic teeth, Theron was pleased with the result, she told The Advocate. "The first day we did all of it [hair and makeup] and I looked in the mirror, I was like [gasps], 'OK, I'm feeling this – this feels very authentic to me and very real and it's not a joke.' I was very happy."