Chris Hemsworth reveals dramatic weight loss for 'In the Heart of the Sea' role

Chris Hemsworth Shows off Scary Slimdown for 'In the Heart of the Sea'
Chris Hemsworth Shows off Scary Slimdown for 'In the Heart of the Sea'

Thor, is that you?

Chris Hemsworth -- who's known for looking good shirtless -- snapped a selfie on Sunday that revealed just how frail-looking he became for his In the Heart of the Sea role.

"Just tried a new diet/training program called Lost At Sea," he Instagrammed to his 869, 000 followers, "Wouldn't recommend it.. #IntheHeartoftheSea"

Ron Howard's action-adventure movie follows the aftermath of the real-life maritime disaster that inspired Herman Melville's Moby Dick. In the winter of 1820, the New England whaling ship Essex was attacked by a whale, leaving the surviving crew to do the unthinkable to stay alive in the face of storms, starvation, panic and despair.

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Hemsworth stars as the vessel's veteran first mate Owen Chase, and revealed to ET that he had to drop a good amount of weight to shoot the shipwrecked scenes.

"We have to shoot the really skinny stuff where we drop down to five, six, 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," the 32-year-old actor said. "I spend more time thinking about food than anything else at the moment."

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In the Heart of the Sea hits theaters Dec. 11.