Yes Mate, I know what you are saying in regards to fasting, and it is something you really want to tune into your bodies awareness with your intuition if you are going to under take such a thing.
It really is something that needs to be taken slowly and mastered over a period of time, with just starting of with one day fasts, then maybe try a 3 day fast after you feel comfortable with a one day fast. The only problem is when folks jump into some 7 day water fast etc straight up and have a major detox overload with massive wastes being dumped into the bodies elimination system and not getting out. So its not using the toxins as a fuel, but it is such a toxic dump on the system if you jump straight into a long term fast.
Basically the body can not detox faster enough so the toxins circulate back into the system, and that is when fasting becomes dangerous.
However before any fast you want to make sure to do a bowel cleanse first. In America
www.blessedherbs.com sells a great bowel cleanse, because yes we want to clean out the bowel, but most importantly we want to strip the built up plaque and mucus of the wall of the intestines and bowel. This compacted mucus on the bowel etc wall is a real problem in today's modern refined food society, even little children have this problem now; See this link (just quickly lol) of what this crap looks like;
http://www.blessedherbs.com/photos2i.html
What is also important if you have done a bowel cleanse, is to make sure that the digestive system is re-balanced with acidophilus and bifida flora;
http://www.gardenoflife.com/detail_primal_defense.shtml Because during fasting the villi that line the gut wall lay down flat along the wall because there is no food being digested, so that is the reason why we want to clean the mucus out of the intestines (plus there is nothing wrong with having a clean bowel). Other wise the villi stick to the mucus during fasting and can not stand back out straight from the wall again once the fast is over and we are digesting again.
We have probably tried every fast under the sun over the years, however one of the best little fasts we found is as follows;
First thing in the morning slowly sip down a glass of diluted fruit juice (according to your metabolic type or blood type diet of fruits that suit you). The fruit juice gets the toxins moving, and of course we want organic fruit freshly made, especially fasting.
Then through out the day drink very diluted wheatgrass juice or liquid chlorophyll (5ml) in pure water, one glass every hour. This keeps that acid being released and detoxified under control.
Then at around 6pm simply drink a glass of diluted vegetable juice (not vegetable broth) according to the vegetables that suit your metabolism or blood type. This gets the toxins to flush out of the body.
Then two more glasses of diluted wheatgrass or liquid chlorophyll before bed; it's as simple as that. Of course after fasting and we begin eating again, we just want to kick back in with light meals and salads etc, maybe fish the next day after that, before getting back into meats etc.
This little program keeps the fasting headaches and detox reaction away and gives you a balanced fast, and less extreme then say a pure water fast with nothing else (Although we have seen the pure grape juice fast work well). So little fasts (1 to 3 days) are o.k, however one of the most important cleanses we can do is stripping and cleaning the intestines and bowel of all that mucus etc and then reflora the lining again.
Of course there are many fasts out there, so just use your intuition and take it easy, fasting is great, but its something you want to master with time, nothing extreme like 40 days and 40 nights in the desert :-).
Shawn