05/23/2014 11:52 am ET Updated May 23, 2014

On-Screen Transformations Prove Some Celebrities Take Method Acting To The Extreme

Some actors take their roles very seriously.

From Matthew McConaughey's 40-pound weight loss for "Dallas Buyers Club" to Bradley Cooper's 40-pound weight gain for "American Sniper," celebrities have the ability to transform their bodies in order to portray certain characters.

Here are 26 stars who took method acting to a whole other level:

  • Ben Affleck
    Zack Snyder/Twitter
    Movie: "Batman v Superman: Dawn of Justice" (2016)
    Role: Batman, the Caped Crusader.
    Weight Gain: Affleck's wife, Jennifer Garner, said he has been working out at least twice a day and that he’s currently sporting 17-inch biceps.
  • Bradley Cooper
    Movie: "American Sniper" (2015)
    Role: Navy SEAL Chris Kyle, the most lethal sniper in American military history with more than 150 confirmed kills.
    Weight Gain: He reportedly gained 40 pounds and grew a beard to star in the film, based on a true story.
  • Chris Hemsworth
    Movie: "Heart of the Sea" (2015)
    Role: One of a few sailors who is lost at sea for 90 days after their ship gets struck by a whale and sinks. (Think "Moby Dick.")
    Weight Loss: After losing 30 pounds for "Rush," Hemsworth crash dieted for Ron Howard's latest movie by eating only 500 calories-a-day.
  • Chris Pratt
    Chris Pratt/Instagram
    Movie: "Guardians of the Galaxy" (2014)
    Role: American pilot named Peter Quill who finds himself the object of a manhunt after stealing an orb coveted by the villainous Ronan.
    Weight Loss: After weighing in at 300 pounds for "Delivery Man," Pratt dropped over 50 pounds for the Marvel movie.
  • Matthew McConaughey
    Focus Features
    Movie: "Dallas Buyers Club" (2013)
    Role: Ron Woodruff, a Texas rodeo cowboy who is diagnosed with HIV and given 30 days to live.
    Weight Loss: More than 40 pounds, eliminated by cardio and diet.
  • Jared Leto
    Movie: "Dallas Buyers Club" (2013)
    Role: Rayon, an HIV-positive transgender woman.
    Weight Loss: “I stopped eating,” Leto told TheWrap of his diet. “It was 30 or 40 pounds. After a while I stopped counting.”
  • Anne Hathaway
    Universal Pictures
    Movie: "Les Misérables" (2012)
    Role: Tuberculosis-afflicted prostitute Fantine.
    Weight Loss: Hathaway lost 25 pounds, 10 before shooting and 15 during. She won the Best Supporting Actress Oscar for the role in 2013.
  • Matthew Fox
    Summit Entertainment
    Movie: "Alex Cross" (2012)
    Role: Picasso, a professional assassin who participates in an underground ultimate-fighting ring.
    Weight Loss: "It was circuit training until I wanted to puke," Fox said of the 40 pounds he shed to play the chronically fit serial killer.
  • Chris Evans
    Marvel Entertainment
    Movie: "Captain America: The First Avenger" (2011)
    Role: Marvel's iconic superhero, Captain America.
    Weight Gain: The 6-foot-3 actor was required to gain over 20 pounds of pure muscle in order to play the action hero.
  • Seth Rogen
    Columbia Pictures
    Movie: "The Green Hornet" (2011)
    Role: Britt Reid aka The Green Hornet.
    Weight Loss: Rogen shed 40 pounds with the help of a personal trainer.
  • Curtis "50 Cent" Jackson
    Movie: "All Things Fall Apart" (2011)
    Role: Deon, a celebrated football player battling cancer.
    Weight Loss: He lost more than 50 pounds.
  • Chris Hemsworth
    Movie: "Thor" (2011)
    Role: Marvel's superhero Thor, the god of Thunder.
    Weight Gain: Hemsworth gained 20 pounds of muscle in order to play the beloved hero.
  • Natalie Portman
    Fox Searchlight
    Movie: "Black Swan" (2010)
    Role: A ballet dancer who slowly loses her mind after nabbing the lead in "Swan Lake."
    Weight Loss: Portman lost 20 pounds to play a ballerina, with director Darren Aronofsky telling Access Hollywood, "At a certain point I looked at [Natalie's] back and she was so skinny and so cut. I was like, 'Natalie, start eating.' I made sure she had a bunch of food in her trailer. She took [the role] very seriously. These dancers get really, really skinny.”
  • Amy Adams
    Relativity Media
    Movie: "The Fighter" (2010)
    Role: Bartending wife of Mickey Ward, Charlene Fleming.
    Weight Gain: "[David O. Russell] said, 'I want you to look like a girl who drinks beer,'" Adams told Parade magazine. So, she did just that.
  • Christian Bale
    Paramount Pictures
    Movie: "The Fighter" (2010)
    Role: Professional boxer Dicky Eklund, who suffered from a crack addiction.
    Weight Loss: "I never got on a scale. I didn't want it to be about the numbers; I wanted it to be about the look," Bale told "Access Hollywood."
  • Matt Damon
    Warner Bros.
    Movie: "The Informant!" (2009)
    Role: Archer Daniels Midland executive Mark Whitacre.
    Weight Gain: Damon gained 30 pounds by eating McDonald's meals, Doritos and beer.
  • Colin Farrell
    Entertainment One
    Movie: "Triage" or "Shell Shock" (2009)
    Role: A photojournalist with PTSD.
    Weight Loss: Farrell lost 44 pounds, thanks to a diet of only tuna, coffee and diet soda.
  • Michael Fassbender
    Icon Film Distribution
    Movie: "Hunger" (2008)
    Role: Bobby Sands, who led a Provisional Irish Republican Army hunger strike in 1981.
    Weight Loss: Fassbender lost 42 pounds after adopting a diet of 600 calories a day, heavy on nuts and berries.
  • George Clooney
    Warner Bros.
    Movie: "Syriana" (2005)
    Role: CIA agent Robert Baer.
    Weight Gain: 30 pounds, with the help of bowls and bowls of pasta
  • Hilary Swank
    Warner Bros.
    Movie: "Million Dollar Baby" (2004)
    Role: Maggie Fitzgerald, who becomes a professional boxer.
    Weight Gain: She gained 19 pounds of muscle and reportedly ate every 90 minutes and consumed 210 grams of protein daily.
  • Christian Bale
    Paramount Classics
    Movie: "The Machinist" (2004)
    Role: A machinist with intense insomnia.
    Weight Loss: Bale dropped 63 pounds. "I had what could be called a kind of stupid feeling of invincibility, like, 'Oh I can do it. I can manage it,'" Bale said.
  • Charlize Theron
    Newmarket Films
    Movie: "Monster" (2003)
    Role: Prostitute and serial killer, Aileen Wuornos.
    Weight Gain: The actress gained 30 pounds (by eating doughnuts) and was almost unrecognizable.
  • Renee Zellweger
    Universal Pictures
    Movie: "Bridget Jones's Diary" (2001)
    Role: Bridget Jones.
    Weight Gain: Zellweger packed on between 20 to 30 pounds to play the leading lady in "Bridget Jones's Diary" and its 2004 sequel, "Bridget Jones's Diary: The Edge of Reason." She credits a lot of "fattening foods."
  • Tom Hanks
    20th Century Fox and Dreamworks
    Movie: "Cast Away" (2000)
    Role: Chuck Noland, a systems analyst whose airplane crashes, leaving him alone in the Pacific Ocean.
    Weight Loss: Hanks gained 50 pounds to portray the pudgy Chuck and then had to shed the weight to depict his growing state of emaciation while stranded.
  • Matt Damon
    20th Century Fox
    Movie: "Courage Under Fire" (1996)
    Role: An Army medic who goes AWOL.
    Weight Loss: 40 pounds, which was reportedly shed via daily running and a diet of chicken breast, egg whites and one plain baked potato per day along with large amounts of coffee and cigarettes.
  • Tom Hanks
    TriStar Pictures
    Movie: "Philadelphia" (1993)
    Role: Andrew Beckett, a lawyer dying of AIDS.
    Weight loss: Hanks lost nearly 30 pounds for the role.