This reminds me of a source of information I was following awhile back, Dr. Tom Chalko from Australia. He described his eventual fasting on only water and Spirulina for protein. The dude loves to wind surf, and supposedly had no complaints of a lack of energy!
He also said that treating food differently is essential to obtain correct fuel for your mind and achieve things like out of body travel, aura perception, and anything else fancy like that. There is so much in the food we eat, so many unnecessary ingredients that we do not even have our bodies natural perception of the effects of what we eat. Ever have a huge turkey dinner and then pass out? Your body needs to SLEEP just to digest! Forget about even a Big-Mac.
This really doesn't seem that far fetched, but you are right about taking it slow. Before fasting people should really consider a minimalistic vegetarian diet for at least a while - and as gross as it is, an enema. There is so much waste clinging to our insides in there, that it will be reabsorbed when the body reacts to the lack of food during fasting - WHICH CAN BE POTENTIALLY POISONOUS.
Fasting has been around forever, and it is only western perceptions that show those who fast as weak and frail. Have you ever met someone who's fasted for an extended period of months to over a year? They don't really seem that much worse off.
Maybe a good middle ground would to be what Dr. Chalko did and at least take a protein supplement... and spirulina is supposed to be the best.