The Role: Steve Rogers/Captain America in Captain America
The Technique: Chris Evans did gym sessions a-plenty and ate lots of protein-rich foods. He said to MTV, "It’s the workouts that, you know, make you want to vomit. It’s horrible."
Did They Keep It Up?: In a word, no, again, to MTV, he said, "Oh my god, when shooting was done I just stopped going to the gym completely for about three months.”
The Role: Bruce Wayne/Batman in Batman Begins
The Technique: Bale went straight from The Machinist where he was 130 pounds, and got to 230 pounds, 40 pounds more than what Christopher Nolan wanted.
He said to IGN, "I couldn't do one push up the first day. All of the muscles were gone, so that was a real tough time of rebuilding all of that."
Did They Keep It Up?: None of his weight-changes have been as drastic as this. However, he has since slimmed down for The Fighter , in the role of heroin addict Dickie Ecklund.
The Role: Logan/Wolverine in X-Men Origins: Wolverine
The Technique: According to Mike Ryan, Jackman's personal trainer, they would train in the morning, so for a 6am filming start, they would be in the gym at 4am, to do an hour and a half of training.
Did They Keep It Up?: Jackman has to get even bigger for The Wolverine , he told the LA Times:
"[Darren Aronofsky] said that Wolverine, in the comics, is powerful, stocky - you know, he's short and thick. So he said, 'I want you to go there, get bigger'."
The Role: Rocky in Rocky
The Technique: For Rocky III , Stallone would do a two mile jog, 18 rounds of sparring, two hours of weightlifting and skipping. Then he would take a nap, go for a run and go for a swim.
Did They Keep It Up?: After Rocky , Stallone's body became instantly recognisable and he's done another five Rocky films and four Rambo films since then. Plus a whole host of other action films.
The Role: Jordan O'Neill in G.I. Jane
The Technique: Moore told Harper's Bazaar, "I just wanted to be believable." And believable she was, after her two hours a day pumping iron and breaking it up with a six-mile run.
Did They Keep It Up?: Well, after 1997, Demi Moore took a break for three years. She said that preparing for the role nearly killed her, but her body isn't looking too bad at all these days.
The Role: Clark Kent/Superman in Superman: The Movie
The Technique: High-protein, weights and 90 minutes on a trampoline. Reeve said to a magazine in 1981, "I put on thirty pounds, all muscle, in fact, I found muscles I never knew I had."
Did They Keep It Up?: He continued the role for another three films, so had to keep in ship-shape for those.
The Role: Micky Ward in The Fighter
The Technique: In 2008, he said, "'I get up everyday at 5am to train for a movie that might not even happen. It's depressing." Training for a film that isn't even definite, there's dedication.
Did They Keep It Up?: Wahlberg didn't keep up quite as intense a workout, but with a Fighter 2 likely to happen, he'll have to get back into shape.
Robert De Niro
The Role: Jake La Motta in Raging Bull
The Technique: De Niro became La Motta. He trained with him, followed his regime and even fought in three organised boxing fights, winning two of them.
Did They Keep It Up?: De Niro has been gaining and losing weight for his roles long before Christian Bale became renowned for it. His rolls have come and gone with his roles.
The Role: Thor in Thor
The Technique: Chris Hemsworth said to Men's Health during his weight-lifting and food-heavy regime, "I ask myself, 'Why am I eating this chicken? For protein. Why am I eating this broccoli? For vitamins and fibre."
Did They Keep It Up?: He dropped his weight a bit after a four-week vacation, saying, "my body doesn't sit at that weight." However, he's kept it up a bit. After all, The Avengers follows closely after.
The Role: Hannibal King in Blade: Trinity
The Technique: Reynolds went from being the scrawny Two Guys, a Girl and a Pizza Place star to a ripped vampire hunter by doing three hour work-outs and having eight to ten meals a day.
Did They Keep It Up?: He didn't do badly, staying muscly for roles in Amityville Horror , X-Men Origins: Wolverine and the recent Green Lantern .