Christian Bale's performance in the new boxing film, The Fighter, is already generating Oscar buzz. The actor dramatically "transformed" himself from Batman buff to "rail thin" for his role as drug addict and former boxer Dicky Eklund. (Watch the trailer for The Fighter.) It's certainly not the first time Bale, and others in Hollywood, have suffered for their art. Here are six notable instances:

Natalie Portman, Black Swan (2010)
The 5-foot-3-inch starlet worked out between five and eight hours a day to shed 20 pounds from her already tiny frame so she could play a prima ballerina. "At a certain point, I looked at [Natalie's] back, and she was so skinny and so cut ... I was like, 'Natalie, start eating,'" says Black Swan director Darren Aronofsky. "I made sure she had a bunch of food in her trailer."

Gwyneth Paltrow, Country Strong (2010)
The lithe blonde had to pack on 20 pounds to play an alcoholic country singer in the upcoming film, a fact that was hard for her longtime personal trainer. "They wanted her to eat a lot of fried chicken," says workout guru Tracy Anderson. "It was frustrating for me, but they wanted her to gain."

Russell Crowe, Body of Lies (2008)
The Aussie packed on 63 pounds to play a CIA veteran in the Ridley Scott spy film. The 40-something actor said it was a very easy process. "At my age ... I have to be really disciplined," he said of his normal efforts to stay slim. "If you take off those disciplines, all hell breaks loose. And it happens pretty quickly."

Christian Bale, The Machinist (2003)
The 6-foot-tall actor dropped 63 pounds to play a chronic insomniac. His secret to dropping all the way down to 122 pounds? Starvation, vitamins, and lots of gym time. As part of the process, Bale consulted a nutritionist who advised him about how much weight he could safely lose — but the actor kept going past that point. "I lost another 20 pounds below what she said I should stop at," he told the BBC.

Renee Zellweger, Bridget Jones's Diary (2001)
The 5-foot-5-inch actress packed on 20 pounds to play the English Everywoman, but she didn't enjoy the overeating. "For two days it's bliss," she said about being able to indulge all her foodie fantasies. "Then after a week your glucose levels are going crazy. You're up and down and all over the place. It doesn't feel good."

Matt Damon, Courage Under Fire (1996)
The 5-foot-11-inch, normally 155-pound actor dropped 40 pounds in four months to play a heroin addict. His dieting secrets? Running 12 miles a day and eating only chicken, egg whites, steamed broccoli, and plain potatoes. "I went too far," he said of the crash diet. "I was getting dizzy spells and hot flashes." Damon suffered from adrenal-gland problems as a result of his dieting, and doctors said he was lucky his heart didn't shrink.

Robert De Niro, Raging Bull (1980)
The pinnacle of sacrificing body mass for art, De Niro gained 60 pounds to play an older version of boxer Jake LaMotta. "Now that's dedication!" says Celebuzz. It paid off: He won his second Oscar for the work.