Taylor Swift’s documentary ‘Miss Americana‘ premiered at the Sundance Film Festival on Thursday night, with fans lining up for hours outside of the venue just to catch a glimpse of the 30-year-old singer arriving on the red carpet.

The most candid and unexpected moment of the Netflix documentary is Swift’s admission of an “unhealthy” relationship with food, revealing that she used to “starve” herself after seeing paparazzi photos she found unfavourable.

In a scene depicting Swift being mobbed by photographers, a voiceover of the singer said, “It’s not good for me to see pictures of myself every day.” She later revealed she used to “starve herself, saying, “It’s only happened a few times, and I’m not in any way proud of it.”

“A picture of me where I feel like I looked like my tummy was too big, or … someone said that I looked pregnant … and that’ll just trigger me to just starve a little bit — just stop eating,” she continued.

Referencing her 1989 album tour in 2015, Swift said, “I thought that I was supposed to feel like I was going to pass out at the end of a show, or in the middle of it. Now I realise, no, if you eat food, have energy, get stronger, you can do all these shows and not feel (enervated).”

TORONTO, ON – OCTOBER 02: Taylor Swift performs onstage during the 1989 World Tour Live in Toronto at Rogers Center on October 2, 2015 in Toronto, Canada.

Swift, who is now a US size 6 (size 10 AU), said she was completely unaware that anything was wrong when she was a size double-zero and that she would pin her weight loss on exercise should anyone bring it up. “‘What are you talking about? Of course I eat… I exercise a lot.’ And I did exercise a lot. But I wasn’t eating,” she said.

In her only interview about the documentary – a Variety cover story timed with the release of the premiere – Swift elaborated, saying, “I didn’t know if I was going to feel comfortable with talking about body image and talking about the stuff I’ve gone through in terms of how unhealthy that’s been for me — my relationship with food and all that over the years.”

She continued: “My relationship with food was exactly the same psychology that I applied to everything else in my life: If I was given a pat on the head, I registered that as good. If I was given a punishment, I registered that as bad.”

Swift said the first time she was featured on the cover of a magazine she was 18 and the headline was, ‘Pregnant at 18?’

“I had worn something that made my lower stomach look not flat,” she said, saying she registered the magazine cover “as punishment,” but that she’d feel praised when she could walk onto the set of a photoshoot and fit into the sample size fashions. “I looked at that as a pat on the head,” she told Variety.

“You register that enough times, and you just start to accommodate everything towards praise and punishment, including your own body.”

“I think I’ve never really wanted to talk about that before, and I’m pretty uncomfortable talking about it now,” she said during the interview. “But in the context of every other thing that I was doing or not doing in my life, I think it makes sense.”

Taylor Swift: Miss Americana premieres on Netflix on January 31st.

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