Zayn Malik suffered from an eating disorder at the height of his One Direction fame.

The 23-year-old found fame as one fifth of the boy band, which was formed on U.K. television show The X Factor, and in his upcoming memoir entitled Zayn, the singer admits he struggled with issues surrounding food when he was a member of the group.

"When I look back at images of myself from around November 2014, before the final tour, I can see how ill I was… Something I've never talked about in public before, but which I have come to terms with since leaving the band, is that I was suffering from an eating disorder," he writes in the tome.

However, Zayn insists his eating disorder didn't stem from concerns about his weight or appearance, but was simply about controlling the food he ate.

"I'd just go for days - sometimes two or three days straight - without eating anything at all. It got quite serious, although at the time I didn't recognize it for what it was," he continues. "I didn't feel like I had control over anything else in my life, but food was something I could control, so I did…"

Coping with an eating issue while being one of the biggest stars in the world led to a difficult time for Zayn, who admits his health took a turn for the worse when the disorder really took hold. He even had to deny claims he was taking drugs when fans began to notice his thin frame.

"I had lost so much weight I had become ill," he revealed in the book. "The workload and the pace of life on the road put together with the pressures and strains of everything going on within the band had badly affected my eating habits."

Zayn appears to have conquered his eating issues and now looks healthier than ever. He has also been struggling with anxiety problems which have led to him canceling gigs, and he opens up about these difficulties in the book, released on 1 November (16).