After years of being famously private, Taylor Swift is opening up in her new documentary, Miss Americana. In the Netflix doc, which premiered at Sundance Film Festival on Thursday, Taylor Swift reveals that she’s struggled with her body image and an eating disorder. Variety reports that in a voiceover in the movie, Swift describes how seeing photos of herself where she looked “too big” or “pregnant” would trigger her “to just starve a little bit — just stop eating.” In an interview for her Variety cover story, Swift explains how fame and scrutiny affected her body image.

“I remember how, when I was 18, that was the first time I was on the cover of a magazine,” she said. “And the headline was like ‘Pregnant at 18?’ And it was because I had worn something that made my lower stomach look not flat. So I just registered that as a punishment. And then I’d walk into a photo shoot and be in the dressing room and somebody who worked at a magazine would say, ‘Oh, wow, this is so amazing that you can fit into the sample sizes. Usually we have to make alterations to the dresses, but we can take them right off the runway and put them on you!’ And I looked at that as a pat on the head. You register that enough times, and you just start to accommodate everything towards praise and punishment, including your own body.”

Swift initially wasn’t sure if she’d feel comfortable enough to talk about her relationship with food in Miss Americana, but says she connected with the way Lana Wilson, the doc’s director, tells the story. “I think I’ve never really wanted to talk about that before, and I’m pretty uncomfortable talking about it now,” she said. “But in the context of every other thing that I was doing or not doing in my life, I think it makes sense [to have it in the film].” Taylor Swift opens up about her family, politics, body image, and more in Miss Americana, out on Netflix January 31.