Good overview - I've been doing a variant of the 5:2 for about 4 years now. I don't eat anything for 24 hours, breaking fast at dinner time around 7pm. In general I've lost some body fat and I feel pretty good for it. I do drink a cup of black coffee in the morning which gives you a terrific boost when fasted.
I've tried recommending fasting to many people but it's difficult to persuade people when the longest they have ever gone without a meal is around 10 hours.