some good advice here in reply to your post.
Fasting is not the ideal method for losing weight for the reason you have already mentioned: the lowering of the metabolic rate.
If you really want to get your life back on track and have abundant energy, then all you have to do is adopt a way of eating that will lose your excess weight more quickly than a water-only-fast, while simultaneously giving you optimum nutrition. This is NOT a deprivation diet.
Google the word Nutritarian, and you will see exactly what I mean.