"My mom flew with me to the rehab centre," she began. "The first day of treatment was the scariest day of my life." Describing her early days in the clinic, she recalled sitting alone in a bare room clutching a stuffed lion that her mother gave to her.

"I worried what people would think. I was battling an eating disorder - but I knew people would assume I was here for other things," the pop star said. "Sure, I've written songs about partying, but my dirty little secret is that I'm actually incredibly responsible."

"But what landed me here?" she asked. After a big tour she felt drained: "My body was shutting down, and I knew why�. I've always tried to be a crusader for loving yourself, but I'd been finding it harder and harder to do personally. I felt like part of my job was to be as skinny as possible, and to make that happen, I had been abusing my body� I had to learn to treat my body with respect.