So eating and drinking in most games directly affects how hungry and thirsty you are. Makes sense to a degree.
But, imagine instead you have a stomach. You eat and drink and fill that stomach, and sometimes a little too much(why you are sluggish and “Fat dumb and happy” after a full meal). Gradually, that stomach empties, making you less thirsty and exhausted.
My idea is to combine the hunger and thirst bar into a fullness bar, indicating how much you can eat or drink. It will slowly deplete, restoring thirst and regenerating energy and health. Basically adding a stomach as a intermediate step. Overeating and fasting both give you debuffs.
Also, you can survive a long time without food, and a few days without water. Maybe we could have the energy bar display calories available, and you need to eat before it gets too low, otherwise you wont have enough calories to digest your food (aka, you starved yourself). Same with water, having the bar show total hydration, changing color as you approach each level of dehydration.
(please excuse my late night post, I’m kinda tired.)