Hi Dana82,
I've been doing a lot of reading since I posted this and now believe that this is a common fallacy. (that fasting is bad because it slows down the metabolism to a point that you quickly gain all the weight back once eating again.) I had wondered at this because I've been fasting on and off for about ten years and this has not been the case for me.

Try reading this page:

http://www.gaianstudies.org/articles4.htm

I think it is a fanstastic, relatively easy read description of all sorts of benefits from water fasting.

Also check out this page:

http://www.lowcarb.ca/tips/tips011.html

but remember that they're talking about cutting out virtually all sources of glucose (sugar) by only eating healthy fats and protein. When we Water Fast we do a similar thing by forcing the body to go into a state of ketosis. This means that we get our energy from stored fats and protein in our body, and since fasting the body starts to get rid of *anything* it does not need (stored toxins in tissues, etc.) and living off of stored fats.
Another fallacy is that when one fasts your body will eat away at your muscles for energy, which can slow your metabolism. The fact is that certain vital functions in our body need a glucose, but only a minimal amount. This *very small amount* can be gotten from converting protein in our muscle to glucose. This is what they are referring to. So it is true, but their point is mute because the amount of glucose need by our bodies is very small.

Now, this may be the most important point I've learned (writing all this is helping me put it all together ;) When we fast we are not producing hardly if any insulin. (Insulin is needed to get rid of too much Sugar or glucose in our blood, else we die) Since we have no Sugar in our blood there is no need for insulin. As a result of this our tissues begin to become more sensitive to insulin. (Too much resistence or insensitivty to insulin is called diabetes type two. It's from eating so much Sugar and grains, for so many years, and flooding our system with many times the amount of insulin we were designed for that we get to a point of being unable to utilise it at all, which than gets dangerous.) Remember, our body always will choose to burn sugar before fat because too much sugar is dangerous. Anyway, as a result of becoming more sensitive again to insulin, our body begins to revert closer to what it was when we were teenagers. ie. we can more easily and quickly burn up sugars and than our body can turn to burning fats and protein for energy. Now this is the key! and also why teenagers are often so skinny in spite of all the junk they eat! They're tissues are still very sensitive to insulin! It takes many years to cause insensitivity. (Notice men in their late 20's and early 30's who had always been skinny begin to get chubby)

Summery of this long paragraph:
After we have a long fast, our bodies are closer to what they were when were teenagers, and thus able to handle the burning of sugars more easily and quickly and thereby more efficient at getting rid of uneeded fat.

cheers,
Jp