Sydney Sweeney Shares How She Gained 30 Pounds for Christy Movie With Fast Food Diet

Sydney Sweeney provided a closer look at the fast food diet she adopted while trying to gain 30 pounds to portray boxer Christy Martin in her new movie, Christy

By Leah Degrazia Nov 10, 2025 9:25 PM
| Updated 2 hours ago
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Sydney Sweeney is allowing fans to be voyeurs into her transformation journey. 

The Euphoria star shared insight into how she gained roughly 30 pounds to portray real-life boxer Christy Martin in her new movie, Christy—and it included a diet heavily made up of fast food. 

In two photos shared to her Instagram Story Nov. 10, Sydney wore two different costumes—a military uniform and a blue oversized T-shirt and jeans—while on set of the drama. In one of the snaps, she's eating an entire pizza pie herself, while in the other, she's enjoying a personal order from Chick-Fil-A. 

Reflecting on her efforts to transform into the athlete, she wrote atop the shots, "Trying hard to keep your calories up lol."

However, a carb-intense diet isn't the only lifestyle change Sydney made for her part in the film, which hit theaters Nov. 7 and also stars Ben Foster, Merritt Wever and Katy M. O'Brian

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In a separate Instagram Story, the Anyone But You actress shared a video of herself doing "workouts between takes." In the clip, Sydney—wearing Christy's white-and-red boxing uniform and curly-haired brown wig—performed some bicep curls with a pair of hot pink 8-pound dumbbells. 

Photo by Denise Truscello/Getty Images for Lionsgate

Indeed, the 27-year-old adopted a grueling fitness regimen ahead of stepping on set for Christy

“I came onboard to play Christy, and I had about three and a half months of training," she told W magazine in an interview published in June. "I started eating. I weight-trained in the morning for an hour, kickboxed midday for about two hours, and then weight-trained again at night for an hour."

By the end of her 30-pound transformation, Sydney admitted she "didn't fit in any of my clothes." 

"But it was amazing," she clarified. "I was so strong, like crazy strong."

For a closer look at Sydney's euphoric transformation into the boxing legend, keep reading. 

Blonde No More

Sydney Sweeney showcased her newly darkened locks while on set in North Carolina for her next film. In the yet-untitled project, the Euphoria star will portray boxing legend Christy Martin, a Hall of Famer who married her former boxing coach James Martin

On-set Strolls

For the role, Sydney traded in her signature blonde hair for a neck-length brunette 'do held back by a navy bandana. She also donned a baggy, zip-up sweatshirt in a navy shade, worn with a yellow-brown T-shirt, dark sweatpants and white sneakers.

A Euphoric Outfit Change

The 27-year-old later donned oversized, knee-length, gray sweat shorts and a light blue tee, while channeling Christy on set.

Ben Foster Also Appears Unrecognizable

Sydney's costar in the film Ben Foster—he'll play James—similarly underwent a major transformation. The Leave No Trace star, who normally rocks a beard, walked on set clean shaven and with a blonde wig. He wore a light blue polo shirt and navy sweatpants while carrying a brown duffel bag.

An Immaculate Third Look

Seen from behind, Sydney walked on set in another set of athletic gear. This time, she wore baggy, maroon athletic shorts and a blue-and-white windbreaker.

Ben Foster Has An Outfit Change

Ben, who shares two children with wife and That '70s Show alum Laura Prepon, changed into a yellow and white striped polo and navy sweatpants for his role as James.

Getting in Character

“I am a very hands-on collaborator,” Sydney told The Los Angeles Times in March 2024. “I like being able to give ideas, be a part of it, help come up with solutions. It just changes the whole process. It’s so hard for me now to be on a set and not be able to help in any type of way and be able to take action. And being able to actually have a voice and have a valued opinion—it means so much.”

Doing Herself Proud

For The White Lotus alum, keeping a packed schedule is not something she shies away from. In fact, she’s always looking forward to what’s next.

"I look up to the older version of myself," she told Women’s Health in 2023. "When I was 10, I looked up to the 25-year-old version of myself, and now I look up to my 50-year-old version. I hope I make the decisions she would be proud of."

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