Fullness
From A KoL Wiki
Fullness is an invisible stat in the kingdom, representing how full you are.
Each character's fullness rating begins at 0 each day after rollover and can be increased by eating food or drinking non-alcoholic beverages. Each such item consumed increases your fullness rating by a fixed value between 1 and 6.
The maximum fullness a character can ever be at is 15. If your character tries to eat something that would bring em over 15 fullness you will simply get a message saying you're too full.