A preview of her interview with ABC's Robin Roberts, posted on the ABC News website, reveals that Lovato opened up to the journalist about her struggle to cope with the effects of bullying as a child.
She told Roberts that she began "compulsively overeating" when she was 8 years old, describing her relationship with food as "really unhealthy" for the past ten years.
The 18-year-old also revealed that she began cutting herself at the age of 11, explaining: "It was a way of expressing my own shame, of myself, on my own body. I was matching the inside to the outside.
"There were some times where my emotions were just so built up, I didn't know what to do. The only way that I could get instant gratification was through an immediate release on myself."
Lovato voluntarily sought treatment for emotional and physical issues towards the end of last year. She returned home in January and has since said that she is looking forward to returning to work.
She added to Roberts: "The real reason why I'm sitting down with you is to open up the eyes of so many young girls, that it doesn't have to be this way."
A preview of the interview will air Friday, April 22 on Good Morning America, with the full interview airing that night on 20/20 at 10pm ET on ABC.
Roberts previously said that she had been "truly touched" by the teenager's openness during the interview, which was taped in New York last month.
> Demi Lovato: 'I had a nervous breakdown'