Valjean is depicted as a gaunt prisoner in the opening act of Tom Hooper's movie musical, adapted from Victor Hugo's much loved classic of the same name.
Jackman, who gained fame for his toned body in the 'X-Men' series, found it tougher to achieve the look, Vulture reported.
"Weirdly, this was almost more physical in a way than an X-Men movie! I was spending even longer in the gym – like three hours in the gym -- because I needed to be as emaciated as possible, but still keep some muscle on for Jean Valjean.
"He's actually written as an ox of a man, so I had to eat seven times a day with no carbohydrates, but then you had the exercise. I'd wake up and do 45 minutes of (cardio) on an empty stomach, eat something, go to the gym, do a vocal warm-up, and then after lunch I'd go back to the gym again. Otherwise, I'd just become skin and bones," Jackman said.
Muscles are back again for Jackman as he prepares to shoot 'The Wolverine'.