Atkins
The Zone
The South Beach Diet
Sureslim
Weight Watchers
The Special K Challenge
Eat, Cheat and Melt the Fat Away
You! On a Diet
Dr. Phil's diet
I can't remember any more off the top of my head, but I've tried all of those. Currently on Weight Watchers, combining all of the knowledge I aquired from reading those books. I do not regret doing any of the diets. I regret not changing my lifestyle in order to stick to them. Along the way I have learned that it's not nutrition which is my lifeline. It's my lifestyle and habits. It does help to have a lot of knowledge, but that will get you nowhere if you don't change the way you live.
I learned the most reading Atkins and The Zone. The Special K Challenge was garbage, utter garbage.