Actually Glen, I read what I wrote and realized I answered it without answering. The biggest problem (i would guess) in long distance running, would be hydration. Your body will not store much water as glycogen/water are stored together. Depleted glycogen stores in muscles leads to less water retention. There is a ratio of water storage:glycogen in muscle cells. I think its 3 grams water:1 gram glycogen or something close. So with depleted glycogen stores, your ability to retain/store water in cells for ready use is retarded somewhat. Also, water you drink will simply be pissed back out. This is part of the reason for carbing up. Also part of the reason for replacing electrolytes. I don't really know what would happen if you just sat and ate a 1/2 a cup of salt and drank a lot of water while in Ketosis. Water tends to be osmotic and passes through cell walls fairly easily as its transported through your blood stream, but i'm guessing it wouldn't help enough, fast enough. You can try it! When you get an intense headache and your skin is suddenly rubbery and losing its elasticity... just stop running and drink water
