The 26-year-old pop star suffered from anorexia for five years prior to her appearance on 'The X Factor' in 2011, when she joined forces with Perrie Edwards, Leigh-Anne Pinnock, and Jesy Nelson to form Little Mix.
Speaking on BBC Sounds Life Hacks podcast 'I've Been There: Jade Thirlwall & Anorexia', she explained: "Anorexia was my own dark secret and I guess I was sort of satisfied with that.
"It was my own thing that I could do to myself and nobody knew about it.
"I obviously became very small and my ribs were sticking out. I was very gaunt and I used to wear a lot of baggy clothes to hide that.
"In my head, I felt so down and depressed about everything that was going on in my life, I really just wanted to sort of waste away.
"I got in a really horrible state. The turning point - and the reason why I first told my counsellor - was when I got tired of hating myself so much.
"The second turning point for me was when I was at hospital and the doctors told me that I would die if I kept doing it. To hear somebody say that to you is actually quite scary and I started to realise how damaging it was for my family.
"I'd become so selfish with how I felt about myself I forgot that I had family and friends who were also really hurting because of what I was doing."
According to Jade, anorexia gave her a misplaced feeling of "control".
She said: "It sounds really weird, but I saw anorexia like an angel on my shoulder. Anorexia for me was control, and if I was controlling something then I was winning.
"It wasn't until I had therapy about it that I realised anorexia was actually the devil on my shoulder. That it wasn't my friend. I really struggled to understand that at first, because I was so isolated and didn't talk to anyone.
"I'd got so used to hearing that voice telling me, 'Don't eat that' or 'Don't look in the mirror', 'You're still ugly, you still have a long way to go.
"It took a long time to realise that voice wasn't good for me any more."