The idea mentioned earlier of having food not heal at all but allow 2-3 short rests per day is a good idea in my opinion. It makes sense when a party is moving through a dangerous area that they might take a short rest after one or more party members are significantly injured. And since short rests are an hour you could concveivable take a couple throughout the day. Perhaps food could add to your short rest heal if they're keen on making it useful. Or make it useless and have the hard mode "tactician" difficulty require your party to eat food each day or risk a progessively worse debuff after a long rest until they eat.