The boys said while the gruelling work schedule for their second album made them more rounded musically, they used to indulge in fast food, reported Daily Mirror.
"We ate loads of fast food while recording. I think we were in one studio for about two weeks and it was just a rotation of a certain Thai restaurant and Portuguese chicken restaurant over and over again," said Harry Styles.
"It's very easy to get stuck in there - you end up with studio tan where you just go green because you've been inside for a week," he added.