You simply must read this post by the marvelous Hillary Monahan.
…it is scientifically proven in a world renown research facility (my basement) by world renowned scientists (my basset hounds) that a writer can perform all basic life functions fueled only by coffee and rage. This can continue for days; the writer consumes caffeine, the mug goes to that place known as THE MUG GRAVEYARD at the back of her desk. Mind you, this particular mutation is not necessarily GOOD for the writer as it’ll inevitably lead to a nervous breakdown and a permanent twitch, but you can spare your writer by delivering actual food once or twice a day. Do this quietly as to not disturb the writer and you may actually get to leave the writing sanctum with all of your phalanges intact.