I found the same to be true!After three days on fruit I got dizzy and fell off scaffolding,had no energy and could see in my stool that i was not really digesting all this fruit! I felt immediately better after eating real food!
The idea that any diet is good for all people is the biggest fraud in the alternative industry,these extreme diets are designed to instill some kind of dependency on their guru to get through the pitfalls of these less then dependable diets!