Starvation happens when you haven't eaten in a very long time (HELP FOOD). 
Bigger races require more sustenance to power their larger bodies, while
smaller races need less food.  Starving begins to drain you of endurance
points.  If you starve long enough, you will begin to take damage.  There
are ways around this hindrance, most notably:
* Races that don't eat.
* A ring of sustenance.
* Satiate person spell.