I am one of the guinea pigs used in the book! I followed the diet for a month and lost 11lbs (not bad at the age of 53)and still follow the principles of it months down the line. I am totally caffeine free (I tried proper coffee a few months ago, and it just made me feel ill), so I only drink de-caff tea and coffee, Roiboos or herbal teas. I no longer take sugar in my hot drinks and cannot stomach really sweet things i.e. chocolate. I can manage some organic plain chocolate from time to time, but I never was a chocoholic anyway.
I used to take lots of indigestion tablets, but have not had one since embarking on this diet and following the principles of it. Ian's diets really do work, and you feel so much better after a month off the alcohol, caffeine, sugar etc. I now take time to have some porridge or muesli before I leave the house to come to work, even if it does mean getting up at 5.30am to do so! The recipes are delicious and really easy to prepare. If you're an imaginative cook you can adapt them for all the family to eat, or to your own taste, but still within the principles of the diet.
I strongly recommend this book to anyone who wants to loose weight sensibly, without starving. Just following it for the month will make you rethink the way you eat.