The 'Game of Thrones' actor Hafþór Júlíus Björnsson reveals body transformation after losing 110 pounds for boxing debut

• Hafþór Júlíus Björnsson is best known as The Mountain on "Game of Thrones."
• The actor has lost more than 100 pounds in preparation for his boxing debut.
• "From 205kg to 155kg," he said on Instagram on Monday.

Hafþór Júlíus Björnsson - best known for his role as The Mountain in "Game of Thrones" - has dropped more than 100 pounds in preparation for his boxing debut.

Alongside acting, Björnsson is also one of the most successful strongman competitors. But the Icelandic native retired from competition in November after winning Iceland's Strongest Man for the 10th consecutive year. He won World's Strongest Man in 2018.

He shared his dramatic weight loss with a picture on Instagram alongside a caption that included: "From 205kg to 155kg."

After his 10th Icelandic strongman win last year, Björnsson wrote on Facebook: "Great way to finish my strongman career. Now a different journey starts and I'm super excited. It's been a great time in the sport of strongman but I've decided that I'm going to take a long break from the sport."

He added: "Maybe I'll never return but never say never right. I'm still only 31 years old and could come back in few years if my heart wants it! Right now my heart tells me that I need to be healthy for my family and do what's best for them! Thanks to you all for your support over the years."

The actor recently shared part of his new fitness regime on his YouTube channel. In the video, he broke down his strict diet, which includes four meals and starts with three eggs and 200 grams of chicken, as well as a smoothie made with 150 grams of yogurt, 100 grams of berries, and 40 grams of oats at breakfast before hitting the gym, where he works on boxing technique with his trainer.

"I'm extremely happy with my shape right now," he said during the video. "When I started this journey, I weighed 205 kilograms. And now I'm down to 155. Feeling good, feeling healthy."

Earlier this month, HBO released three official photographs from the set of the upcoming "Game of Thrones" prequel series titled "House of the Dragon." Matt Smith, Emma D'Arcy, and Olivia Cooke can all be seen in costume.

"House of the Dragon" will take place about 200 years before the events of "Game of Thrones."