User blog comment:Kuopiofi/Saitama - Absolute or Supernatural?/@comment-24053170-20160907020749/@comment-24053170-20160907042823

Take Zeref (fairy tail) for example, due to his curse of immortality he doesn't actually need to eat or sleep. He simply does it to pass the time. In fact in the entire series Zeref if never shown eating anything. All we see him do is drink water and nothing more.

And considering that his curse wouldn't let him die even if he didn't sleep or eat proves that its unnecessary for him.