Actors will put themselves through cruel and unusual punishment for roles - to be fair, they should, considering how much they get paid to get into character, and how way too many of the best paid ones seem intent on merely playing themselves anyway. They will throw themselves into preparation, often spending months in character, or shadowing real-life versions of the characters they are set to play, until they confident and comfortable enough to successfully ape the way their character should act or speak. But when a role requires a physical transformation, the dedication needed to pull of the change, and to maintain a physical peak for the duration of filming (or in the case of some, to drop and gain weight dramatically for one performance - see Christian Bale in The Machinist, for instance) really must be admired on a different level. There is very little an actor can do to pretend they are muscle-bound, and there's no way to fool an audience into believing the character spends a lot of time in the gym, unless the actor is willing to (aside from CGI, which tends to take away some of the relatable side of the character.) This sort of transformation takes a lot more than the usual Method approach - it's not just about getting under the skin or behind the eyes of a character and then relying on "acting" to get by - it's about sweating and giving yourself up to a gruelling, intense regime, knowing the pay-off will be temporary and for the benefit of someone else. It's about eating steak and eggs multiple times a day, hitting the gym endlessly, feeling the burn, using pre- and post-workout protein supplements or whey powders, dunking in ice baths for repair, and fundamentally changing the way you live for a relatively short contract. Now that is dedication.
5. Tom Hardy - The Dark Knight Rises
Hardy was hardly a small guy before he was cast as iconic villain Bane for Chris Nolan's trilogy ender, but his transformation from early careers roles (like his naked appearance in the excellent HBO series Band Of Brothers) is incredible. For Rises, Hardy piled on muscle weight, turning himself into a hulk to carry the very real threat to Batman on his gigantic shoulders.
4. Mickey Rourke - The Wrestler
Some could have been forgiven for thinking Rourke's career was over after some disastrous choices, but The Wrestler represented a short-lived rejuvenation for the journeyman actor, and his tender performance was brilliantly balanced by his authentic physical transformation into The Ram. The demands of the training apparently pushed Nic Cage out of the role, but Rourke blossomed, bulking massively and looking nothing like his early career self in Aronoksky's squared circle.
3. Robert DeNiro - Raging Bull
Whenever physical transformations for movie roles come up, talk quickly turns to DeNiro's iconic boxing role, and though the most impressive element was the weight he put on to portray LaMotta in the dark days beyond his career, the actor also incredibly conditioned himself for the fighting scenes, turning himself from a relatively slight frame to an authentically large heavyweight in an impressive period of time. This is still the benchmark - and though Christian Bale's haunting transformation for The Machinist ranks up there, it is far easier to lose weight dramatically than it is to bulk and condition.
2. Edward Norton - American History X
Though Norton's despicable skin-head is entirely unlikable for the first part of the movie, the transformation that the actor went through to bring him to screen is no less impressive. Bulking from the same gawky frame used so well later in The Incredible Hulk and Fight Club, Norton is a genuine physical threat, bulked in his upper body to an unrecognisable shape and conditioned to have one of the most memorable six-packs in Hollywood history.
1. Gerard Butler - 300
The top of this list couldn't go anywhere else. Though both DeNiro and Norton bulked impressively, they were never subjected to the same kind of work-out that Butler and the rest of the 300 cast were charged with undertaking to prepare for the comic book movie. The regime was brutal and unforgiving, but the results were incredible (even if some actors' efforts were supplmented with CGI and make-up to highlight muscle shapes) and it must have taken an awful lot of protein, and a huge number of ice baths to heal those work-out tears. Did we miss any other actors who seriously bulked up for roles? Share your own picks below.