Admittedly seeing this very, very late, but maybe I can still help.
Cosmo_AC, I'm guessing that you don't really want to run overly much with an actual system but want to make sure that the effects of supplies are covered. This is an assumption on my part so feel free to correct me if I'm wrong.
Given this, I suggest doing research for the effects of starvation, dehydration and so on. I would personally likely handle it by describing the effects for people who just aren't eating or drinking. Some people object to having their character affected in such a way, but I've always felt that GMs may employ at least a little privilege therein with player consent. In survival/horror, players can almost certainly expect to be messed with one way or another anyway.
If they don't eat, start out with hunger rumblings at inopportune moments. Characters will start getting the shakes and mess things up when they should otherwise have gone well. All movement starts to become painful. Characters briefly hallucinate wondrous food only to find themselves gnawing at pebbles. A dehydrated character who puts a piece of candy into her mouth can't get it to start dissolving because she doesn't have any saliva left.
If you don't want or don't have sufficient time to do research, just keep individual notes on people and start tossing out penalties when, in your opinion, they aren't properly playing out the effects.
I hope that helps some.