It's not unusual for the most dedicated of actors to want to drop a couple of dress sizes for an upcoming movie role, but some stars take it to a whole new level when their character requires them to look, well, a little ill. Chris Hemsworth, best known for playing Norse God of Thunder Thor, is the latest to shock us with his brutal transformation.

Just tried a new diet/training program called "Lost At Sea". Wouldn't recommend it.. #IntheHeartoftheSea

A photo posted by Chris Hemsworth (@chrishemsworth) on

We never fail to be shocked by the extreme measures actors will take to achieve character representation in a movie; whether it's bulking up in about 6 months to play a buff superhero, or waving farewell to dignity and shaving off all their hair. But the one thing that always gets us is those extreme weight loss routines. Hemsworth has, indeed, gone skeletal for his role in 'In the Heart of the Sea' after living off just 500 calories a day. But how many more stars have risked their health for an Oscar?

More: Watch the trailer for 'In The Heart Of The Sea'

1. Christian Bale - 'The Dark Knight' star is probably one of the most famous actors to have undergone an extreme weight loss programme for a film. In 2004, it was revealed that he had dropped a massive 62 pounds (28kg) to play emaciated insomniac Trevor Reznik in Brad Anderson's The Machinist'.

2. Matthew McConaughey - Not far behind in the weight loss stakes was McConaughey in 'Dallas Buyers Club', where he played real life AIDS victim Ron Woodroof in the 2013 biopic. He managed to lose a total of 50 pounds (22kg), while his co-star Jared Leto lost 30 pounds. It was worth it in the end, though, as both landed Oscars for their respective roles.

Matthew McConaugheyMatthew McConaughey looked positively emaciated for 'Dallas Buyers Club' role

3. Mila Kunis - It's not just the men whose devotion to the camera has led to dangerous methods of transformation. Both Mila Kunis and Natalie Portman had to get their weight down in order to play lithe ballerinas in the 2010 Oscar winning Darren Aronofsky film 'Black Swan'. Kunis worked hard to regain the 20 pounds she lost as soon as possible after her gruelling training programme.

4. Jake Gyllenhaal - When photos emerged from the set of 2014 thriller 'Nightcrawler', the media was shocked over the gaunt appearance of Gyllenhaal. In the movie, he plays a photographer who attempts to be first on the scene to shoot major crime scenes for the press. It seems to have been largely Gyllenhaal's choice to drop 20 pounds once he found his interpretation of the character, and he surprised us further when he was also hospitalised on set for cutting his hand after punching a mirror. Now that's dedication.

Jake GyllenhaalJake Gyllenhaal was unrecognisable on the set of 'Nightcrawler'

5. Tom Hanks - Hanks notably lost 35 pounds for his role as a gay lawyer with AIDS in 1993's 'Philadelphia'. On the one hand, it landed him his first Academy Award, but on the other hand, his fluctuating weight has taking its toll on Hanks over the years and he has consequently been diagnosed with Type 2 diabetes.

6. Matt Damon - Weight loss ventures of this kind have a lot of other health implications, too. So much so that director Ridley Scott pointedly refused to let Damon slim down for his latest film 'The Martian'. Although, the star has been known to undertake such drastic measures; he lost 40 pounds (18 kg) in just 100 days in order to play a drug addict in 1996's 'Courage Under Fire'.

7. Anne Hathaway - Hathaway was so concerned about the impact her skeletal appearance would have on other girls during the filming of 'Les Miserables' in which she played the poverty-stricken prostitute Fantine, that she has refused to reveal details of her diet at the time. She did admit to losing 25 pounds, with the help of a nutritionist, but reportedly became so skinny that she broke her arm in a fall.

Anne HathawayAnne Hathaway worried her weight loss would encourage her young fans

8. 50 Cent - For someone who has to stay in shape for months at a time during touring, this rapper took a big risk when he fell below 11 stone to play a cancer-stricken American football player in 2011's 'Things Fall Apart'. 'Get Rich or Die Tryin' indeed.