Re: hopinso...

No, that's not why you're receiving the cautions. Prolonged fasting as a weight loss method is only about 5% effective. It leads to a yo-yo effect. It will slow your metabolism so much, that you must be on a strict diet for 6 weeks after the fast until the metabolism begins to pick up. Think about this, you fast for quick results, but you still have to diet afterward to maintain the loss.
In the meantime, anything over 10 days without doctor supervision has the potential for illness and complications, especially electrolyte depletion.
There is a fast, much less dangerous, and easier method. Eat every other day. Fast every other day, and on the fasting day you can eat raw fruit. This will keep your metabolism up, you'll probably lose as much or more weight. Plan a good nutrition program using the books hopinso suggested.
It's not "that's that" I'm sorry to say. There is a lot biologically that has to be understood. I have done prolonged fasting and if you have, you know how slow your metabolism gets. You're sending your body a starvation method. While great for healing and rejuvenation, a prolonged fast is not the best choice for weight loss. Check some of my previous posts, previous posts by hopinso and mikeritr for more info. I wouldn't even attempt a fast without consulting the two books above. They give you the physiological information to make an informed choice.