Sydney Sweeney is opening up about her dramatic transformation to portray legendary boxer Christy Martin in an upcoming biopic. In a new interview with W Magazine published Monday, the actress revealed she spent months training for the role, gaining 30 pounds and going up four pant sizes in the process.

The Emmy nominee revealed that “my body was completely different” because of all the training, which led to her not being able to “fit in any of my clothes.”