Preface: I just read this:
I’m trying to outline here a framework for a more detailed, but hopefully not too painful system regarding hunger, hydration, health/immune system, and as they relate to temperature and physical exertion, or the lack thereof. Currently characters have simple hunger and thirst gauges, and the hidden health gauge. Firstly we need more gauges, hidden or otherwise. I’m suggesting we measure 1) protein intake, 2) calorie intake, 3) vitamin & nutrient intake and 4) hydration. Those four, plus enjoyment, should be the attributes that all food items should have. Each element could be stored in the body, up to a maximum. We should therefore have two separate storing mechanisms for each four nutritional element as they enter the body. First would be storage #1, the immediate storage. I suppose this would be the stomach. Storage #2, the body, would be your longterm storage. A small portion of the nutrients of each food item that the character would consume, would be transferred to storage #2. The presence of nutritional elements in storage #2 would cause various effects on the character, specifically in the high and low extremes. Storage #1 would be tied to hunger effects, and its status would be a subject to rapid changes. Storage #2 would be slower to change in either direction, and of course it would be tied to Storage #1’s received input. As a starting point, I would suggest that 5% of all nutrients of all consumed items would end up in Storage #2 over the time they are digested, regardless of exertion/exercise. It is an open question how much energy should be derived from Storages #1 and #2 as the player faces exertion. In the end, not all consumed nutrients are exploited by the body, which means some or most of what we eat goes to waste.
I would tie each character’s protein intake requirements to starting Strength. That is to say, the stronger you begin with, the more protein you require in your diet. Deficiency would result in faster fatigue, reduced speed, lowered health/immune system and lowered focus. Excess, on the other hand, would turn into calories, or fat, as it does IRL. It could be debatable if protein requirements should be tied to current strength, and not starting strength. Both would have different longterm gameplay consequences. Both would make sense in their own way. Additionally, high protein intake, with proper exercise, could eventually grant a minor strength bonus, which should require constant upkeep if the player wishes to maintain the bonus. Similarly, lack of protein, or too much exercise without sufficient protein intake, could result in weakness, a status effect. I will deal with exercise later below.
This would be the main replacement of the current Hunger gauge. You could store calories by eating excessively, and eventually obtain obesity. Obesity, or its opposite, emaciation, would both be potential status effects such as pain or hunger. I will explain more in-depth further below.
Vitamins & nutrients
I would not propose changes to the way vitamins are stored, as I don’t fully understand the current health/immune system mechanics. However, lack of vitamins in Storage #2 could produce a variety of negative status effects.
How to define and measure exertion? I would tie this to the raw weight of currently carried items. Each step taken would require certain amount of calories and hydration, and moreso when running, swimming or cycling. Also collective encumbrance on legs, torso and arms could be a factor. Special attention should be paid and penalties should be applied if characters persistently move around overburdened (weight). At the very least, their calorie and protein requirements should be increased. On the other hand, this could be the only way to gain bonus strength.
How to measure received exercise? Should it be tied to raw calorie consumption? Or should the game also consider the amount of tiles walked/run per day, not to forget swimming and cycling. Should melee combat count as exercise? Could one swing with a 1kg item count as 1 unit of exercise? Would that be the same as taking one walking step while carrying a 50kg load? Could exercise be “stored” in the body the same way as vitamins and fat? Those could be starting points for measuring fitness.
Exertion and temperature
Currently, I believe, thirst rate is increased if the character spends too much time in hot environment. Similar mechanic should be tied to hunger and cold environments. Characters should lose calories faster from storage #2 if they spend time in cold environments without proper warm clothing. But that could and should also be detrimental to immune system. All exertion, in turn, should produce body heat, but also increasing calorie and hydration consumption at the same time.
Exercise and health
Exercise could be added as a need, same as hunger and thirst currently. In the bad cases, you either get too much of it (in relation to nutrient intake), or not enough it, causing accumulation of fat or “obesity”.
If the player consistently exceeds his calorie requirements, the excess should be stored as “fat”. Your first sign of your excessive calorie intake would be the status effect Obesity -1%. Obese characters could have higher resistance to cold, not only by having better heat capacity, but also the better ability to produce more body heat at the expense of the fat storages, up to a point. You couldn’t be able to lose all your fat just by sleeping in the cold for a month straight… No, you would get sick first. Obese characters should be able to freeze to death after all. Obese characters would run and (possibly) act slower and they would get exerted faster.
Emaciation is the opposite of obesity. You have not been eating enough, and it shows. “Emaciation -1%” status effect would be your first warning sign. Emaciated characters would be bit like obese characters, except without resistance to cold. They might even be more vulnerable to cold than normal. They would be slower, weaker and tire faster in general, requiring more sleep, and getting exerted faster.
As with most things in delevopment, this would all be a gargantuan balancing act. The design and its complexity could be made clear but it would take some serious testing to make sure the system would still be functional and enjoyable. Of course if we know and remember the relevant numbers and pre-existing statistics with clarity, then any further features will be implemented with less trial and error. How many steps does an average CDDA character walk per day? What lengths should we go to force a healthy lifestyle on RPG characters? How harshly should negligence be punished? I suppose a smooth but certain demise, with plenty of time for course correction is the wisest route.