I know that humans doodling around the office use 1800 to 2200 calories a day, averaging 2000. Billy boy the football star may be up around 2500 to 3000, as is the warehouse worker.
But what is food?
Food is something that the body oxidizes to produce chemical energy. There are 2 main channels of chemical process to do this; sugar and fat.
PROTEINS are long complex molecules made out of enzymes. These chemical robots can do amazing things, and are VERY useful tools in chemistry, or biochemistry. We make all of these we need from enzymes.
ENZYMES are moderately long molecules made out of many different sorts of sugar molecules. While not a capable as proteins, they can do some pretty interesting things. We make these, all but 8, which we get from our diet.
SUGAR is a small ring molecule of carbon, hydrogen, and oxygen, most commonly C6H12O6. It is very similar to alcohol, and this is why alcohol screws up sugar management chemistry in the body, producing interesting sensations.
CARBOS (sugar, starches) are 4 calories per gram. Starches are complicated molecules made of sugar molecules, and once broken down (DIGESTED) into it's component molecules, results in sugar. So is protein, as digestion breaks this down into enzymes, and these in turn in to the sugar molecules they are made out of! But this long involved sequence takes MUCH longer, almost as long as the involved process of making energy out of FATTY ACIDS- the things we call lard, fat, and oil.
FAT is processed along a different sequence, and provides 9 calories per gram of fatty acids oxidized. Burning fat does not involve any sugar metabolism, but produces Ketosic acids, which smell REAL BAD, and give carnivores their characteristic bad breath.
DRAGONS AND OTHER CARNIVORES smell bad for this reason; scavengers which eat dead old tainted meat also absorb the breakdown products of the decay, and smell even worse-no one wants to French kiss a VULTURE!
MEAT is about 30% fat, 60% protein, and 10% indigestible gristle, ( & bone, hair, etc,) which does not contain calories we can use. (YES, lean mean athletic adventurers have a lower body % of fat, more like 10%.) Fat is 9 calories per gram. Protein, starch, and sugar all are 4 calories per gram. So on the average of 30%/60%/10%, critters in general are gonna provide 5.1 calories per gram of critter- that is, 10 grams of critter eaten becomes (27 calories from fat, 24 calories from protein/enzymes/sugars, totaling 51 calories)=5.1 calories per gram of critter- for humans, elves, dwarves, fairies, etc. Goats and horses and a few others are able to ferment the cellulose in grain to make more calories come out of it, and goats can break down almost anything with that 4 rumen stomach, so can get calories out of USED LAUNDRY FABRIC SOFTENER SHEETS, paper bags and labels, rags, and hair! (all of which is treated as complex starches, at 4 calories per gram).
This means a human on a 2200 calorie a day diet is going to burn 2000/5.1=390 grams of stuff a day to live, plus about 1 gallon of water. But a active warrior burns a lot more, ESPECIALLY when they face enemies. US Army estimates show that the soldier on the battlefield burn from 5,000 to 10,000 calories a day when in combat conditions. EVEN LYING STILL the heart is racing, and the body is burning out heat and energy like a power house. ASSUME 4000 calories for a human under such conditions, OR MORE. IF you are a warrior, and a BIG FELLA, assume more like 7000-10000. Of course, mages burn some up also, but not as bad, and should generally be at the low end of 4000 calories.
Note that meat becomes blood sugar slowly. FAT becomes energy, but not EVER as sugar, even more slowly. Starches become sugar fairly fast (baked potato anyone?) but are not balanced sources of all 8 enzymes we have to have to live. Note that RAW potato is tough and hard to digest, and also contains chemicals that make most people sick- which break down easily when heated to about the boiling point of water for a while. A small amount of rations should be sweet, such as candy or honey, a somewhat larger amount be grains and/or starchy roots, and the lion's share in proteins, such as cheese or meat. WHOLE grains have high vitamin content, and are to be favored in the ration mix- they can even be sprouted for increased vitamin content.
Honey or SUGAR is pure carbohydrate, and RACES into the bloodstream fastest of all- especially GLUCOSE. Sweets are a quick restorative after a battle- once the gut calms down and the heart rate comes back to something close to normal. Milk sugar is somewhat slow, as it has to be converted in the stomach before absorption before we can use it. NO sugar intensive food is nutritious, containing ONLY energy, and requires other things to provide minerals, vitamins, micronutrients, and ALL 8 ENZYMES.
CHEESE is the perfect way to preserve milk. LIFE is the perfect way to preserve meat. But hauling a few live chickens down some smelly hole is not so good an idea. Now if you can get over the squeamish thought of eating the fallen enemy (your enemies the monsters certainly have no such scruples!), here is an ideal source of FRESH MEAT. Just make sure you cook it completely, as they tend to carry diseases communicable to similar species- just like pig and man, monkey and man, so cook they enemies like roast pork and you'll do ok.
Cheese and beans provide all 8 enzymes required for a complete balanced 'protein' diet. We cannot make these 8 enzymes; all others we can make out of simpler molecules, and with enzymes we can make any protein we need. Dried beans store well, just soak in a crock or pot, boil, and mash. Add a pinch of salt, a little sausage grease, and fry some flower and water on a pan to make flat bread. Spread mashed beans on flat bread with thin slices of cheese. VIOLA! LUNCH! Ok, so we fart some.
IF you have a good spice bag, so much the better. Dried spices are lightweight, and some at least are inexpensive, and make a world of difference. ALWAYS make sure you add a little salt to anything boiled. Onions are pretty cheap, store well, are light, and flavor nicely.
Preserved sausage links were invented as a military ration- the meat can be carried many days without refrigeration, and does not spoil. If you fry them, save the grease for the beans, it adds to the flavor and to the fat content (beans have none).
When the rations start to run low, EAT THE ENEMY. Note this calls for cooking, which calls for heat, usually fire, unless you have a mage with a cook or heat spell handy. AGAIN, cook well done to prevent diseases. Always add salt to anything boiled, as this draws salt out of the meat.
AND REMEMBER: cooking one's friends is in very questionable taste.
