And the answer to your other question is yes, it does slow down your metabolism after a few days, but it isn't permanent. It returns back to normal once you eat again. The thing I noticed is that I felt more energetic after the fast than I did before. Late in the fast though I felt very low in energy. I think the end result was worth it though because overall I am lighter and I feel a lot better.
The fear of the metabolism slowing down comes from mainstream marketing dogma. And it has even trickled its way into fasting literature. As an example, why do you think Martin Berkhan recommends an 8 hour eating window and not smaller? It's because he still thinks that going longer will result in the muscles melting off, even though there is no scientific evidence to support it!