During his final days in One Direction, many saw that Zayn Malik looked unhappy.
But very few noticed that the singer was rapidly losing weight, and that he was quickly developing an issue with eating.
In his new self-titled book, Zayn, 23, has opened up about how he regularly went days without eating anything at all, as he was suffering from an eating disorder.
He wrote: "When I look back at images of myself from around November 2014, 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."
But Zayn says the illness wasn't triggered by any issues with his appearance.
"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," Zayn explained, in an extract obtained by The Sun.
"It got quite serious, although at the time I didn’t recognise it for what it was."
Months later in March 2015, Zayn broke millions of fans hearts when he decided to leave the band – though ultimately it sounds like it was the right move.
The singer, who is currently dating supermodel Gigi Hadid, 21, seems to have recovered from the disorder, but still suffers from anxiety.
He has been forced to pull out of charity gig Autism Rocks in Dubai next month as he feels he is not "sufficiently confident" performing on his own.
Zayn faced a similar turmoil earlier this summer, when his anxiety forced him to pull out of the Capital FM Summertime ball just 90 minutes before he was due to go on stage.
Fair play to Zayn for being so open about his issues. BIG HUG.