Realisticly, you have
Stamina - The amount by which you can exsert your self, like jumping, running, carrying large heavy things.
Energy or Fatigue - The willingness of your charictor to do things, walk, use stamina, talk ect. this is like long term stamina.
Don\'t forget, most real people do things because there body tells them to, have compleat control of your charictor is unrealistic to begin with (not that it\'s not easy to program for) but it gets round the problems like running into walls, people don\'t run into walls, because it would hurt. and there body realy says it\'s not a good idea.
When your tired, you should get warnings, then you should go to sleep if it becomes extream, with the option of posible spells or drinks to keep you awake (but take away acrasy interlect and a few other stats)
the effectivness of such a system is hard to imagen, if say you only exist when your loged on, then that solves any problems relating to going to sleep while loged off, and/or getting killed, you can be safe in the knolege that you will reapear in the same place, perhaps you should drop things that don\'t belong to you when you diapear, I don\'t know. obvously this would allow you to get out of battles and such.
regaining long term energy should be quick, scince time is warped in all games to allow for the game to be interesting, perhaps 5 or 10min in a nice warm bed should do it. and it would take hours to go down (in real time). short term stamina should be managed as a proccess of energy / exertion, if you run you use energy and exsert yourself and the stamana should say how long you could keep that kind of exertion going before requiring a pause or a sit down.
Food, although food is always an interesting idea, it\'s never been implermented in a nice way, the Sims did it ok, but then they had access to a fridge ;-). perhaps eating could improve your life bar, or better still have it as speed loss/ energy gain variable, the more you eat the more you need to exert in order to move, but the more energy you \'ve got, if you don\'t eat you should just lose your energy more quikly but NOT die.
Some food for thought anyway.
-- DoctorMO --