Sydney Sweeney is allowing fans to be voyeurs into her transformation journey.

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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 , Sweeney 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."

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