Sydney Sweeney gains 13 kg to portray boxing legend

Filming began in September 2024 and the movie is scheduled to premiere at the Toronto International Film Festival in September 2025. On July 22, Sweeney shared the first on-set photo with her 25.2 million Instagram followers.

"Her journey is a testament to resilience, strength, and hope, and I’m honored to step into her shoes to share her powerful story with you all," Sweeney wrote.

Sweeney’s physical preparation drew attention from fans and media. According to Marca, the American actress had to gain 13 kg, increasing her weight from 52 kg to 65 kg, mostly in muscle mass, for the role.

To prepare, Sweeney spent three and a half months training intensively. Her routine included weightlifting for one hour in the morning, two hours of kickboxing in the afternoon, and another hour of weight training in the evening. The transformation forced her to leave behind her old clothes.

"I'm usually a size 23 in jeans, and I was wearing a size 27. My boobs got bigger. And my butt got huge. It was crazy!" Sweeney told W Magazine.

Sweeney, 27, learned wrestling and kickboxing from age 12 to 19. Though she had taken a break from the sport, she was eager to return to the ring and fully committed to capturing Christy’s essence.

"Christy Martin's story is not exactly light, it is physically and mentally demanding, but I love to challenge myself... I feel compelled to tell the story of a woman who faced so much adversity and didn't let it defeat her," Sweeney said.

Christy Martin, born in 1968 in West Virginia, was a professional boxer from 1989 to 2012. She held the WBC super welterweight title (66.7–69.9 kg) in 2009 and ended her career with 49 wins (31 by knockout), seven losses and three draws. Nicknamed the "Coal Miner’s Daughter," she was inducted into the International Boxing Hall of Fame in 2020, the first year women were included.

Outside the ring, Christy's life has been documented in the film Untold: Deal with the Devil and her memoir Fighting for Survival.

"My story is about sexuality. It's about domestic violence. It's about child sexual abuse," she said.

Christy Martin (R) practices with her ex-husband James Martin. Photo by Netflix

Christy revealed she was sexually abused as a child by a family acquaintance. She realized she was a lesbian in fifth grade and fell in love with a teammate on her high school basketball team, The Guardian reported.

In 1991, at age 22, Christy married her manager, James Martin, then 47. She described it as a "marriage of convenience" and later accused him of both physical and psychological abuse. James allegedly used cocaine to control her and spent her prize money on a lavish lifestyle.

In 2010, Christy announced her intention to divorce James. In November of that year, James shot her in the chest and stabbed her multiple times, then fled the scene. Remarkably, Christy survived.

James later attempted suicide but failed and was arrested a week after the attack. In 2012, he was convicted of second-degree attempted murder, sentenced to 25 years in prison, and died in November 2024.