Celebrity Chris Hemsworth Looks Almost Unrecognizable as He Reveals 500-Calorie Diet For 'In the Heart of the Sea' Chris Hemsworth looked especially frail in the picture, showing off his ribs as he sported a scraggly beard and cuts on his chest and face By Jodi Guglielmi Jodi Guglielmi Instagram Twitter Writer-Reporter, PEOPLE People Editorial Guidelines Published on November 23, 2015 10:30 AM Share Tweet Pin Email Photo: Courtesy Chris Hemsworth Where did Chris Hemsworth go? Hemsworth took to Instagram on Sunday to reveal his dramatic weight loss transformation for his upcoming film In the Heart of the Sea, adding that he consumed as few as 500 calories a day to prepare himself for the role. The Australian actor, 32 – who is known for his fit physique and even landed PEOPLE’s Sexiest Man Alive title in 2014 – looked especially frail in the picture, showing off his ribs as he sported a scraggly beard and cuts on his chest and face. Hemsworth revealed that in order to film the shipwrecked scenes, he had to go on strict diet to drop the pounds. “We have to shoot the really skinny stuff where we drop down to 500, 600, 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,” Hemsworth told Entertainment Tonight at the time. “I spend more time thinking about food than anything else at the moment.” “Just tried a new diet/training program called Lost At Sea,” he captioned the almost unrecognizable photo of himself. “Wouldn’t recommend it #IntheHeartoftheSea.” In the Heart of the Sea follows the doomed crew of the whaling ship Essex after it is assaulted by a massive whale in 1820 – a true story that formed the basis of Herman Melville’s classic novel Moby Dick. In the film, Hemsworth stars as Owen Chase, the vessel’s first mate and one of the men who spends 90 days stranded at sea after the whale destroys their ship. In the Heart of the Sea hits theaters Dec. 11.