The producers of the film claim that Christian Bale dropped from 173 pounds to 120 for the shooting of the movie. They said he wanted to drop all the way down to 100 but they would not let him for fear of health reasons. Bale's diet consisted of one can of tuna and one apple a day.
The 63 pounds he lost is said to be a record for any actor who lost weight for a role.
He gained the weight back in time for the shooting of Batman Begins (2005)