He was SO skinny during that time, so we knew something had to have been going on...

Zayn Malik has been open about struggling with anxiety, and now the singer is getting candid in his new book Zayn about suffering from an eating disorder during his One Direction days.

"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 wrote.

The "Pillow Talk" crooner goes on to explain his issue didn't center around his looks or his weight, and he actually didn't see it as a problem at first.

"It wasn’t as though I had any concerns about my weight or anything like that, 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 revealed.

He ultimately realized that he was desperately looking for a way to handle his chaotic lifestyle.

"I didn’t feel like I had control over anything else in my life, but food was something I could control, so I did. I had lost so much weight I had become ill. 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," he confessed.

He's not ashamed to discuss mental health, something he made clear when he canceled shows this past June and September.

"Dear fans, I have been working over the last three months to overcome my extreme anxiety around major live solo performances. I feel I am making progress but I have today acknowledged that I do not feel sufficiently confident to move forward with the planned show in Dubai in October … I am truly sorry to disappoint you. I hope to see you all soon. Thank you to all my fans who support me globally. With love and respect always, Zayn," he said in a statement last month.

We applaud him for being so honest.