You can create your own packages and even package templates. You can make an NPC travel somewhere, and here's a hard part because you want him to automatically look for a nearby food merchant. I think you need to use keywords although I've never done that so I don't know how exactly do they work.
Then you would have to script it so the NPC eats some food shorlty after visiting a merchant. You'd do this in a Begin/End/Change tab. In order to make it seem more realistic you might make some dialogue. Then you'd just need to set a schedule.
However I think that some NPCs already go to a market and as for buying -- and
having to buy... You won't get a complete simulation here. Firstly, how would that even look? There's no animation for handing an object, as far as I'm aware. So it would be just an NPC standing in front of a seller and then eating cheese. Secondly, if you want to have scripts that add items to NPC's inventories, check if they're not possibly hungry or whatever... Why? Most players won't observe nuances like this or they simply won't care. Even if they wanted this kind of realism it still wouldn't affect them as they couldn't look into this NPC's inventory or ask him about his addiction, nor would he really die from it (would he?), nor would he need to sell his stuff...
You know, this game's not a simulation, everything that's there exists because it matters to a player.
I'm sure you know what you're doing but remember to consider things like this, if you haven't already.