*Having not read responses*
That could be interesting if you had a hunting and gathering option - special wildlife that could be shot with a bow or dispatched with a sword that became food. How it could go could depend upon the seriousnessness of the game: a Twilight Princess "grit" style game would have you hunting squirrels, rabbits and deer - type creatures. A Toon Link adventure might have you setting your sword to walking sandwich-monsters.
I'm not sure I'd like it at all, though as metered, a necessity. It's already kind of annoying to have to spend all my rupees on potions sometimes when I'm trying to earn enough for a special item. Food would be over the top. From what I did skim of this thread, people already talked of the Skyward Sword stamina meter. Personally, I found it kind of annoying. It was great in-concept because my very favorite game outside of the Zelda series has something similar as a vital part of the gameplay - and it works exceptionally well in that game, but its implementation in Skyward made Link rather... *weak.* It ran out too soon and a lot of the areas where he had to use climbing or running stamina felt like they were made with contrived difficulty.
I do like the idea of food being more important in the series. The foods we've seen - milk, pumpkin soup and the like are really cute additions to the games, but I think what I'd like to see is something like an option for Link to order a meal at an inn, different foods with different prices - a cheap sandwich gives him a three heart refill, a fish n ' chips platter gives him a five heart, etc. All the way to a steak dinner or something that gives an all heart fill - but it's something for him to do at an inn, like the healing properties of beds in Skyloft in Skyward Sword. I'd like to see food as an option, but not a metered "you will have issues out in the field" thing. Technically, if that were the case, he should be having issues holding his bow and sword after getting standard injuries.
The water thing - I can see that as a very specific sidequest run or a "get to the temple" quest. Link is given water and told that the game's desert-temple is some miles ahead. Once he steps into the desert, he has a "water meter" to gauge how much he is drinking as he wanders across the burning desert. If he runs out, he starts losing a bit of life (kind of like the Temple of the Ocean King in Phantom Hourglass when the Hourglass is empty). He gets to the temple and is safe and hitting a switch at the temple entrace releases oasis floodgates so the dry rivers he wandered past are filled, meaning "there is water there" and he doesn't have to do the water-gauge trek again. You know, a one-time thing.