Sydney Sweeney gained over 30 pounds on a diet of Chick-fil-A and milkshakes and trained three times daily to portray legendary boxer Christy Martin in the new film "Christy."

Sydney Sweeney stars in 'Christy,' a Christy Martin biopic. At the Toronto International Film Festival on Sept. 5, she thanked the boxing legend herself, recalling her training regimen and that it was both 'a dream' and 'scary' to have Martin on set.

Sydney Sweeney stepped into the spotlight at the Toronto International Film Festival with the premiere of Christy, a biopic about legendary boxer Christy Martin. The actress opened up about the demanding physical preparation she went through to play the role.