Some stars go to great lengths to get into character. Matthew McConaughey, Anne Hathaway, Renee Zellweger, and Christian Bale are just a few of the many celebrities who've lost or gained significant amounts of weight for movies
Matthew Fox in Alex Cross
The Lost alum was almost unrecognizable after losing 40 pounds to play a cage-fighting assassin in 2012's Alex Cross. "I played college football [at Columbia]. I thought I knew my way around exercise," he said of his grueling, five-month circuit training regimen for the role. "Either I was wrong, or things have changed drastically. Maybe it's both. This was full-bore. Many times I felt like throwing up."