As it currently stands, a survivor is capable of living on just meat and perhaps a vitamin pill or two, even longterm.
I believe that this should change, a more varied diet should be a requirement for long term survival.
A quick search yields that a human needs the following basic nutrients to stay properly fed:
- proteins
- fats
- carbohydrates
- minerals
- vitamins
- water
or alternatively translated into the following picture:

This could be implemented into the game (in a simplified way) by keeping track of how many grams of type of food the survivor has eaten.
A survivor would then need to fill part of his diet up with plant matter/vegetables and fruit and the occasional fish, instead of just meat.
Besides a fitting CBM/mutation that could show your current balance of nutrients, you could get helpfull text hints whenever you are missing something specific:
"You sure could go for an apple right now!"
Or in a more severe case:
“You crave for some delicious red meat!”
Keeping a proper diet should provide the survivor with a small lasting bonus to his morale (+5, like optimist), and a small buff to his stats (+5 movement speed? + disease resistant).
Likewise, not following a proper diet, should give a penalty to morale and stats. Starting off small, but getting larger the longer the survivor neglects his diet.
To counteract the fact that a survivor suddenly needs to watch what he eats, less food needed a day could suffice.
I think having a proper diet in the cataclysm is an important factor in survival, and this suggestion could help that in the right direction.
Tell me what you guys think about this.