Perhaps I am spending too much time on levels and backtracking a lot, but I am having difficulty finding enough food to keep my nutrition up high enough. And since I can't seem to be able to eat the dead, what other ways are there to gain food?
Don't keep the kind of a stash that you'll want to visit periodically - consumables aren't worth starving. Come back only for great gear that synergizes with some other great item you just found. If you're holding an armload of unidentified potions and scrolls, stand near some water and ID a few the hard way. At later depths, you'll appreciate being able to decide on the spot whether the consumables you find are worth keeping, using, or leaving on the ground.
Build your strategy around rings, enchanted items, and higher-quality items in roughly that order. E.G., your inventory is full, you've found a ring of wisdom, a couple staves, and platemail. Platemail is nice, but you don't own a ring of regeneration therefore a warrior build will have difficulty succeeding - dump any weapons and armor that you can't currently equip, don't come back for them without an exceptionally good reason. You need to keep exploring and finding new food with a minimum of inventory-juggling. Better versions of what you passed up can appear at later depths anyways.
I hope that helps! I die pretty often myself, but so far it has never been to the food lock.