Chris Hemsworth survived on 500 calories a day while shooting 'In the Heart of the Sea'.

The Australian actor, who recently wrapped shooting the upcoming disaster film directed by Ron Howard, embarked on an extreme diet for ''three or four weeks'' in a bid to slim down to play shipwrecked sailor Owen Chase.

Speaking on the set, the 32-year-old star said: ''We have to shoot the really skinny stuff where we drop down to 5, 6, 700 calories a day, a good three or four weeks and it's going to be pretty uncomfortable, but we'll be together in our misery.''

While Chris was happy to transform his body for the role, he admitted giving up his favourite food, including ''all the bad stuff, burgers, chocolate, ice-cream,'' is never easy.

He told 'Entertainment Tonight': ''Anything that is not on the menu is automatically something that you have an absolute obsession with. I spend more time thinking about food than anything else at the moment.''

Ron got tips from his close friend Tom Hanks, who has lost a dramatic amount of weight for roles in the past, including 'Cast Away,' on the healthiest way to get the cast to lose weight.

The filmmaker said: ''He gave me some good clues and he also said you know, 'make sure it's organised, it's healthy.' ''