During the press conference for MBC's 'Weightlifting Fairy Kim Bok Joo' on November 15, Lee Sung Kyung talked about the hardships of playing her character, Kim Bok Joo. She always had a very slim frame, so it was hard for her to gain weight for the role. What was particularly hard were the time strains.
She said, "I finished my previous production and within fifteen days, started filming this one. I had no choice but to bloat. That's why I'd eat the day before and go [to filming] bloated."
Also, she revealed that the image she was going for was healthy. "Rather than plump, I put focus on emphasizing healthiness while forming my body," she revealed. She also revealed there were a lot of people who did weightlifting who were actually skinny in real life. She said, "While training in weightlifting, I am diligently gaining weight. I'm in the midst of completing a muscular body."
Good luck! It's admirable you took on this challenge!