Way it's working right now is that if Food/Fullness, aka hunger, is less than 100% then the maximum Stamina you can have is also reduced.
Say you haven't bought into the Attribute that increases Stamina pool by 10 points each time. So your max Stamina = 100 , then as you get hungry, so below 100, your resting Stamina will only fill up to that number.
So a Fullness/Food of '75' means Stamina won't go above 75.
What the "oversaturation" allows is for you to eat so Food/Fullness is greater than 100. Max Stamina would still be 100, but since the over-eaten bit is being used up first (though hidden), your Stamina will keep refilling to 100 for a number of minutes; until the oversaturation has been consumed and Fullness drops below 100.
Additionally Water plays into max cap for Stamina. Think if your Water drops below 50 then stamina pool shrinks? Sry, not clear on the water part.
But basically you want/need to keep Hunger/Food/Fullness pretty darn high all the time. Otherwise your stamina pool is smaller, so fewer melee swings before you're out of stamina and can't swing until it comes back, or shorter distance you can sprint before you're forced to walk.
To me Water & Food should be reversed in their effects on Stamina. But atm, Food has the main impact on Stamina.
Sry the explanation is such a mess. Partly due to my poor writing, also partly the system being a bit messy, imo.
Ha! I see what you did there! Pretty good/true one though