Hunger is the craving for food, both in real life and in Apocalypse Rising. In Apocalypse Rising, hunger is displayed as a green bar on the bottom side of the screen. As time passes, the bar will slowly consume due to player activites. Unlike thirst, hunger depletes slighty slower than thirst. To replenish the hunger bar, one must find food in the game, which can be found nearly anywhere. If the hunger bar is completely consumed, the result will be starvation and your player's health bar will slowly start to deplete, resulting in death sooner or later.
The survival perk can help slow down the process of the hunger bar going down also. In Kin Reborn with the towns spread apart, food is more important than ever.