To play Jean Valjean in Les Misérables , when he is a prisoner and in bad shape, Hugh Jackman wanted to prepare himself physically.
The scenes in the film where his character is physically damaged were shot first. So he was able to go on a diet beforehand to lose weight, and he grew a long, bushy beard.
But for the two days before filming these scenes, Jackman stopped hydrating. He didn’t drink anything for over 36 hours. His goal was to lose water around the eyes and cheeks, so he would look dried out, old and sickly.
After filming these scenes, he shaved and returned to a normal diet in order to play the healthy, wealthy Jean Valjean of the rest of the film.