Snails are a fairly bad source of food, actually.
If I were you, I would keep a lookout for secret passages and the like. I have found more than enough bread/scarabs/maggots on a stick and stuff like that.
The thing about snails is that while their food only restores about half like every other food, it weighs 2-5 times as much!
This is the case with most dropped foods in the dungeon, as far as I am aware.
The lightest of them are Herder Caps, but those are still quite heavy.
I suppose it's intended to stop people from doing exactly what you are looking for: supporting themselves indefinitely without any sort of major drawback.

So if you want to carry something besides your chow and have a sizable stockpile, you'd better start looking for some of the things i talked about.