Skarsgard went to extreme lengths to get his incredibly ripped body for the film, including eating 7,000 calories a day.
For three months before filming started, the True Blood star tripled his food intake and lifted heavy weights to add 25 lbs. of muscle to his frame. He trained with his friend Magnus Lygdbäck, a trainer-nutritionist also from Sweden.
Once he arrived on set, he followed a strict no sugar, gluten, wheat, dairy or alcohol regimen, eating six small meals throughout the day and working out twice a day for the next six months.
Skarsgard and Chung were first spotted looking cozy together in February, taking in a Father John Misty Show at New York's Bowery Ballroom.
In March, they arrived together at Paris's Gare de Nord and were later seen holding hands at celeb hot sport Caviar Kaspia.
The Legend of Tarzan is in theaters now.