Chris Hemsworth may be best known for looking like a Norse god, but to play a 19th-century sailor stranded at sea, the In the Heart of the Sea star had to slim down considerably. Now, Hemsworth has shared a photo of just how radical his transformation was.

“Just tried a new diet/training program called ‘Lost at Sea,’” Hemsworth wrote on Twitter. “Wouldn’t recommend it.”

Hemsworth talked to EW earlier this summer about the grueling effort that went in to losing so much weight. He said that he was already considerably under his “Thor weight” after slimming down for the thriller Black Hat, and losing the last 15 pounds for In the Heart of the Sea was exhausting.

“When you’re already starting off lean, its brutal to chew through that kind of weight,” Hemsworth said. “Every pound feels like a kilogram.”

Hemsworth stars as real-life first mate Owen Chase, who served on the whaling ship Essex and was stranded at sea after a whale destroyed the ship. To play men cast adrift with no food, Hemsworth and his co-stars reduced their diets to a measly 500 calories a day.

“They had to work out every day, even on shooting days,” director Ron Howard told EW. “Because they had to lose the weight pretty fast and they had to lose it safely. They needed to keep burning the calories and we also needed that sinewy strength that was more of that era, as opposed to a kind of cut, buff look.”

In the Heart of the Sea opens Dec. 11.

In the Heart of the Sea
2015 movie
  • Movie
  • 121 minutes