This author purports that an individual's blood type should determine what foods to eat and which ones to avoid. Eating the wrong foods, according to D'Adamo (a naturopathic doctor), would have the same affect on the red blood cells as administering the wrong blood to someone during a transfusion.

The rationale behind this plan is the biggest stretch of all and reaches comic proportions. His theory tries to tie in the evolution of man with changing blood types and diets. Any long term success with this plan is an accident based on switching food intake to something more agreeable to your digestive physiology or your frame of mind when you entered the program (in other words, how important was it for you to lose weight).

The Downside

No credible scientist supports the theory described in this book. The most often cited fallacies in this book are the relationship between blood type and disease and the assumptions made about the diet of early man. And, of course, there is no record of success with this plan.