I have fasted, not for days at a time, but for time periods (sunup to sundown) extended over many days. I know that my body does not function well towards the end of the day. I tire easy and become lethargic, get headaches, my mind is not as sharp and my overall output is hampered significantly. However, I do notice my body over time (days) will adapt slightly to the change, such as getting fewer headaches.

I would think that one’s overall fitness, current weight and if still eating to some extent (eating limited meals), dietary input (fats vs. carbohydrates) will effect how well or poorly, one will respond to fasting. I see no problem in trying short term fasting either for a given time period each day or totally for several days to get a feel for how one’s body and mind might react to short, medium and long term fasting during the course of routine activity.

Pete.

many have fasted for a month or more. a lot depends upon how active you are, and how fat (and fit) you were before you started the fast. 22 miles a week of walking is nothing. Just an hour's mild walk per day, unless the terrain is really terrible, which is unlikely for a test.

Two years ago on April 15th I took a solo hike up Snake Den Ridge Trail in the Smokies. I was carrying a 50 pound pack, not in good enough shape. It began to snow as I started about 8a.m. Because of my age, lack of fitness, and pack I proceeded extremely slowly. Because of the snow and 28 degree weather I did not want to stop as there was no place to sit on the narrow rocky trail. I had a good breakfast before starting but did not eat during the day. My feet were wet from crossing streams.
Long story, short, I came down with hypothermia (?) about 4pm. I knew enough to realize I was in trouble. I stopped, pitched my tent, heated water, ate, drank, and survived.
Moral? Lack of energy provided by food contributes to Hypothermia very quickly.

But in the immediate term (next 30 minutes), the hot food did more than the food ever could, to keep you running.

Remember, calories are a measure of heat. Cooked and hot food is free calories. <img src="/images/graemlins/smile.gif" alt="" />