4. Christian Bale
Our favorite Batman (no, not Affleck) once had to drain himself of all calories and weight in order to play the role of a chronic insomniac in the film Machinist. A single look at Bale in that movie is bound to move you and make you realize how much work he had to put in to look like a poverty ridden man. He was so skinny, you could almost see his bones. He weighed only 122 pounds and at 6 feet tall, one can only imagine how slim he was. He did mention that he took supplements to get his required vitamins but he hardly ate during that time and pushed his body to the limits with the exercise routines.