Sydney Sweeney loved transforming her body for her upcoming Christy Martin biopic. "I felt very strong and powerful," Sweeney, 27, told Vanity Fair in an interview published on Thursday, September 4. "I loved it. Being able to lose myself to become a vessel for somebody else is my dream." The actress gained between 30 and 35 pounds to portray the former professional boxer in the film and spent three months boxing for several hours a day, as well as weight training and working with a nutritionist.