Chris Hemsworth had to look really skinny for his role in his upcoming movie “In The Heart Of The Sea” and the actor was asked to survive on a diet of about 500 calories a day. Hemsworth describes the whole experience of eating less as miserable and said he has now developed an obsession for junk food.

Hemsworth, 31, who is used to bulking up his muscles for various movies including “Thor,” “The Dark World” and “Avengers: Age of Ultron,” found it extremely difficult to restrict his diet and lose all the muscle for his new movie. Hemsworth plays a skinny sailor in “In The Heart Of The Sea,” who gets lost at the sea without food and water. For his new look, he did not eat well for nearly a month.

"We have to shoot the really skinny stuff where we drop down to 5[00], 6[00], 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," he told ET Online. "I spend more time thinking about food than anything else at the moment."

Hemsworth also admitted he found himself craving certain high calorie foods during the starvation period. The actor found it tough not to give in to the temptation of eating junk food. "All the bad stuff -- pizza, hamburgers, chocolate, ice cream. ... Anything that is not on the menu, it automatically is something that you have an absolute obsession with," he told the website.

For his role in “Thor,” the actor had to look bulked-up, so he gained 20 pounds. But the real challenge came when he had to lose more than 40 pounds for his new movie. "After all that dieting, if I see one more serving of chicken breast with biologically grown broccoli, I swear that I'm going to take Thor's hammer to the plate," the actor joked in an interview with OK magazine (via Belfast Telegraph). “In The Heart Of The Sea” is scheduled for a Dec. 11 release in U.S.