Why stop at drinking and eating, you know what would ad to the realism of the game, having to take a dump every 24 hours (depending of course on what you ate you having to choose between 200 year old canned goods and radiated rats, and there could be a meeter between constipation and diarrhea,), oh and after that you should wipe your ass and hide your feces, as it is also a survival matter, as anybody who was in the boy scouts knows that wiping your ass in the great outdoors without proper toilet paper (especially in the desert were plants are few most of them being radioactive cactus) can have serious effects causing focusing issues, and awareness loss (yeah scratching your ass during targeting could really fuck up your aim). Hiding your feces is also detrimental to your survival if you are being hunted by a deathclaw or by those pesky tribals for example.
You see how ridiculous this sounds???? Stop trying to make games realistic, they are only GAMES for havens sakes, they are made to relax you and make you forget about REAL life for a little while. If you want realism you don't have to join the army or something just step out the god damn door. there is enough realism out there.