Christian Bale

In 2004 the actor lost almost 70 lbs. for his role in The Machinist. Then in 2005, he bulked up significantly to play Batman in Batman Begins. Once again in 2010, he shed several pounds for his role in The Fighter. He told MTV News: "I didn't look at numbers, I didn't look at scale, I just went down to what looked like might be the right body type for Dicky and the way that he fights as well."