Thanks for your comments Fonty, I will buy a book or two and visit him again, by which time he will probably be home. Given that he is on oxygen and can't move about and is really fed up with it (wants to go down the pub with his mates), I think he will be eager to read it. I was thinking of getting Fasting: The Ultimate Diet, by Allan Cott, which is the one the girl in the Youtube video mentioned it, but Chris (if you are reading) I would appreciate any recommendations. I guess something that explains the basics well and is easy to read would suit him. He used to be in electronics, and has a fairly analytical mind. Always asks for explanations, even when things are way beyond his field of knowledge (eg about networked computers). He is very inquisitive.