The 30-year-old singer spoke about her issues with food in the film, which premiered at the 2020 Sundance Film Festival on Thursday night, January 23, 2020, explaining that sometimes trolls' comments about her appearance led her to "starve a little bit."
"(If I'd see) 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 said.
Further explaining why she'd decided to speak publicly about her eating disorder, Taylor told Variety that it was the film's director Lana Wilson who made her realise that it "made sense" as part of the documentary.
"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 explained.
"But the way that Lana tells the story, it really makes sense. I'm not as articulate as I should be about this topic because there are so many people who could talk about it in a better way. But all I know is my own experience. And 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."
"I remember how, when I was 18, that was the first time I was on the cover of a magazine," she continued. "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 photoshoot 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."
However, Taylor added that she's been able to conquer her eating disorder enough that she's now "really happy" - despite the tough times her loved ones have been through recently, including her mum's brain tumour diagnosis.
"I know that there's a lot of bad stuff that's gone on recently, a lot of really hard stuff my family is going through, and a lot of opposition and feeling pressure or suppression of one kind or another," she said. "But I am actually really happy. Because I pick and choose now, for the most part, what I care deeply about. And I think that's made a huge difference."