I've been playing the iOS version of Craft the World for a while now, on and off, and it's alot of fun (I always play sandbox mode - don't ask me about the campaigns or whatever they're called - I can't be arsed), but I find myself constantly starving for Coal, mostly because my vertically challenged dudes keep asking for food, and apart from one item all the barely decent food requires Coal to cook, meaning I can only use some of the Coal I mine to make Steel Ingots (and later Silver Ingots).
So I decided to throw my brain at the problem and do an actual analysis of which foods represent the best and most efficient usage of Coal.
What I've found is that the most efficient food comes fairly early (I call is tier 1.5 because it's neither from Basic Cooking nor Advanced Cooking, but from the Fishing tech). It's Grilled Fish. This gives 15 feed value per 1 Coal used. Can't top that!
You can't go 100% Grilled Fish, though, as your facially be-haired dudes will eventually complain about lack of varied diet. The best variation to provide them with, as much as possible, is Apple Pie. That gives only 12 feed value per 1 Coal used, but also gives +2% healing when eaten (Grilled Fish doesn't).
If that doesn't satisfy, try Bread (12 feed/Coal but no healing, and made from Flour which can be farmed) and Stew (made from Meat which must be gathered, but it's the best food to make from Meat). Neither of those accelerate the healing of the eater, but that's 4 different dishes which hopefully will keep your dudes happy for a long time.
When they start complaining (if they do - I have yet to actually try this myself, since I only started making this analysis now, after abandoning my latest on-going game), give them Fish Stew (10 feed/Coal) and Grilled Meat (9 feed/Coal), neither of which has medical properties.
The last two Coal-cooked foods are Buns (6 feed/Coal) and Fried Eggs (6 feed/Coal) none of which heal.
Salad Greens is a very good early game food, unlocked with Basic Cooking, because it requires no Coal to make (and also no kind of kitchen crafting station).
Before Basic Cooking you must feed your dudes Apples, Berries and Cones, but try to give them primarily Cones as those have no other use. Apples heal them 2% per gulp, Berries don't, but you'll need lots of Berries for non-food purposes later in the game, whereas the Apples appear to be plentiful.
Early game, I'd probably feed my dudes 1/2 Apples and 1/2 Cones, or 2/3 Cones and 1/3 Apples.
After Basic Cooking I'd go for 2/3 Greens Salad and 1/3 Grilled Meat.
Once I unlock Fishing, it's as much Grilled Fish as the dudes will tolerate, with Salad Greens for variety.
Finally, upon unlocking Advanced Cooking, combine the Grilled Fish with Apple Pie. I suggest 2/5 Grilled Fish, 2/5 Apple Pie, 1/10 Bread and 1/10 Stew.
Or maybe roughly 1/3 each of Apple Pie, Salad Greens and Grilled Fish, throwing some Bread and Stew onto the tables only when your dudes start grumping about lack of varied diet.
Or perhaps more simply, I might go with 4 Tables for food, one with all Grilled Fish, one with all Apple Pie, one with Salad Greens, and the last usually empty but throwing some Bread and Stew onto it when the dudes start complaining.
Heres the total list of feed-per-Coal for all Coal-cooked foods. Tied entries are sorted according to secondary criteria.
15 Grilled Fish
12 Apple Pie (also heals)
12 Bread (no healing)
12 Stew (no healing)
10 Fish Stew (a waste of Fish)
9 Grilled Meat (best use of Coal for cooking, early game)
6 Bun (superior to fried Eggs, because you become able to farm Flour)
6 Fried Eggs
∞ Salad Greens
Eggs and Apples appear to be plentiful, Leaves too. Water can be gathered in huge quantities. Flour can be farmed. Meat isn't rare either, but Fish you can have by the hundreds, if you find some good lakes (or landscape engineer one, or use landscape engineering to improve an already existing lake). Berries aren't a concern either, but all the same I'd try to avoid feeding my dudes Berries if possible, since they're used to make Oil which is used both for Grilled Fish and for various non-food purposes.
Best use of Eggs: Apple pie
Best use of Meat: Stew
Best us of Fish: Grilled Fish
Best use of Flour: Apple Pie (but bread is secondary)
The three foods that heal are: Apple, Greens Salad, Apple Pie. All gives +2% healing rate per food item eaten, and it appears to be a property of the Apple itself, transferred in undilluted form to any dish made with Apples.
Having done the "math" I now feel silly about having made so many Fried Eggs in particular. What a waste of Coal!