Chaz and Hector are absolutely right. Food and drink are fuel. Carrying it in your pack doesn't do you a darn bit of good.

If you have ever participated in any kind of endurance event such as a bicycle race or long distance touring, long distance swim or triathalon, you should understand the importance of carbo loading and hydration.

I've done all of these at various times and I can assure you, if you don't carbo load and drink, you are pretty much cooked. Try cross-country skiing towing a sled for a few hours without eating or riding 50 miles on a fully loaded touring bike and see how you feel.

I would start carbo loading a few days in advance-lots of pasta or whatever you like, but lots of calories.

Also, get plenty of electrolytes. When I was teaching scuba diving, I was constantly eating something, so I didn't get muscle cramps in my legs while diving and I was in pretty good shape at the time. I still got them once in a while, but if I didn't eat, it was pretty much a sure thing.