22 Stars Who Went to Crazy Body Extremes for Roles

You may not recognize Gladiator Russell Crowe these days—because he's currently quite a bit heavier, bald, and sporting an impressive beard for his role as Biblical figure Noah. Crowe has had some prior experience gaining weight for a movie role—he packed on 63 pounds for Body of Lies in 2008—and some feared for his health during that stint. Celebuzz and the Huffington Post round up 21 other celebs who have undergone dramatic body transformations for their films:

• Matthew McConaughey: The frequently-shirtless star is decidedly less buff now that he's playing an HIV patient in upcoming movie The Dallas Buyer's Club, for which he is losing 30 pounds. "I should not look healthy by the time I'm doing that film," he recently said.

• Mila Kunis: She's gone to both extremes, dropping to 95 pounds to play a ballerina in Black Swan and, this year, gaining weight for her upcoming role in tk.
• Beyonce: She lost 20 pounds while filming Dreamgirls, because she wanted the audience to see a real difference between "young Deena" and "old Deena."
• Matt Damon: When he lost 50 pounds in 1996 for Courage Under Fire, he actually damaged his adrenal glands. Then, in 2009, he gained 30 pounds for The Informant.
• Jared Leto: To play John Lennon's assassin in Chapter 27, he gained an incredible 67 pounds—then went on a crazy diet involving water, lemon, and cayenne pepper to lose it.

Click for the full list from the Huffington Post, or check out the list from Celebuzz—which includes an actress who got to gorge on donuts and pizza. (More celebrity stories.)