From what I remember, the sensation of being hungry is a human sensation, and it kinda means that they are too attached to the human world, hence a trait common with Hollows... So that was one of the big problems when Urahara was trying to make Ichigo a Shinigami, almost turning him into a Hollow...


Hunger was also mentioned in the young Rukia flashback, and it showed a different nature to this hunger... though I don't remember what it was...