Watch: Why Sydney Sweeney Says She "Loved" Grueling Workouts for Christy Role Sydney Sweeney's transformation into her latest role was immaculate. Indeed, the actress shared that the process of bulking up 30 pounds to play professional boxer Christy Martin in the Christy biopic was a euphoric experience more than anything. "It was probably one of the most amazing, fun experiences," Sydney exclusively told E! News' Francesca Amiker ahead of the world premiere at the 2025 Toronto International Film Festival on Sept. 5. "I was a very happy person, and I became so strong. I felt so good.