Well if you have some kind of rest mechanic , don't allow the p.cs to use it unless they have food to cross off.
after every bit in the game like a combat or a challenge or some other physically tiring thing the players have to cross off a ration or cross off something else on their character sheet like armour class or Strength or Saving throws and then anything to do with that fails until they have something to eat.
when the player has to roll dice after a period of non-dice rolling activity ask them to cross off a ration. If they don't have any rations to cross off they must of skipped lunch or breakfast or something. Then for this and further rolls they can only use the worst die at the game table, the one that everyone hates and distrusts.
have food restore hitpoints like 86.5% of video games . Just can't use it in combat. Come on it's not that much of kludge and it beats the awkward shoehorning of minor healing potions in the game or damn clerics or whatever. Maybe if you dropped below half health or zero you can't heal with food ?
A rule of thumb for assigning healing values is:
Default is 1d8 for cheap, long lasting (tack and cheese for example)
add another 1d8 for any of these : extremely fresh, rare /expensive, spoils quickly
SOME TOTALLY DELICIOUS AND LONG-LIVED FOODS
1. Wax sealed crab shells with the flesh "cooked" and partially fermented with lemon juice and capers. Deplug and suck out
2. Molass sugared tongue slivers in a bamboo tubes. Chewy , like gamey liquorice
3. Bog Butter
4. Cow Blood and Milk in a gourd
5. Salty Greens , Limes , and Blood Pudding
6. Flour deliberately invested with large worms. Don't eat all the worms and there will be more later! Hoorah! Unless the flour goes off , then it might hallucinogenic
7. Bracket fungus , with apple cider vinegar to soften it for chewing
8. Roast Fern Heads and Crickets
9. Pickled Pigs Feet. Collagen! Good for muscle recovery!
10. Roast ants and raisins
11. Sprouted grains and dried mushrooms
12. Mushy monkey brains in brine
13. Gingered dried banana and lard blocks
14. Pressed seed cakes
15. Cornbread with fizzy root jam
16. Dog sausage and pear thick cider stout
17. Honey curds and lily rhizome
18. Kelp Porridge in shark egg cases
19. Ostrich egg
20. Dried figs and goat skin strips