is updating fans on his fitness journey!
The actor about his weight loss and body transformation on Instagram Tuesday, sharing before and after photos from the last year.
He wrote: "From 205kg to 155kg," which is about 451 pounds to 341 pounds.
Björnsson — who is best known for his role as Gregor "The Mountain" Clegane on GoT — used to compete in Strongman competitions.
He announced his retirement last year after winning Iceland's Strongest Man title for the 10th consecutive year.
"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 wrote in a post at the time.
"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!"
Björnsson shares a son — who was born in September — with his wife, fitness trainer .
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"Our beautiful baby boy made his grand entrance into the world at 11:19 AM on September 26th 2020 after a short and intense six hours. 3530 grams and 52 cm. The birth was the most powerful, life changing, empowering thing I've ever done in my entire life. We are all doing well and settling in at home as three!" Henson shared on Instagram after welcoming her son.
The actor also shared the story of their son's birth. "After an extremely hard 2 hours and 19 mins of pushing our healthy, strong, beautiful boy arrived weighing 3530 grams, 52 cm long," he said. "To finish the most beautiful, awe inspiring labour was the most wonderful phone call to my daughter to introduce her to her new little brother."
Björnsson is also dad to daughter Theresa Líf, whom he shares with his ex-girlfriend Thelma Björk Steimann.
The GoT star and Henson in his native Iceland.
"It is with great pleasure that I now get to call Kelsey Morgan Henson my wife!" Björnsson captioned a photo of himself holding his bride up on their wedding day.