Hugh Jackman consumed "nothing but water" for 36 hours to prepare for 'Les Miserables'.
The Australian actor has seen his 'Wolverine' filming delayed so tried to keep in peak physical condition in preparation for the role - but then needed a dramatic transformation when he had to start work on the musical before the action film.
He explained: "We were going to shoot ['The Wolverine'] last year and from then it was, 'Are we going to start in July? Are we going to start in August? Are we going to start in November?'
"So for the last year I've been staying in the vicinity of where I need to be. Then when I got 'Les Miserables', Tom [Hooper, director] said, 'You know, when we find you you're straight out of prison, which is effectively a labour camp. I need you to be worryingly thin, sunken cheeks...'
"I was like, 'Oh my god!' So I worked my a**e off for the beginning of that film - I went for the old water diet thing where it's nothing but water for 36 hours."
These days, Hugh is working on re-gaining the weight he lost as he is finally ready to shoot 'The Wolverine'.
He told Total Film magazine: "I've just come back from eating my eighth chicken breast of the day.
"I'm 14kg heavier than I was three months ago, so my body is going to need a break after this one."