"Eat Right for Your Type" was written by Peter J. Adamo. The diet instructs you to use your blood type to determine which foods you should be eating. According to Adamo, when you eat foods that "agree" with your blood type, you reduce the risk of cancer, heart disease, diabetes, infections, and liver disease. According to his theories, blood types correspond to the following ancestry:
Does this pass the smell taste? Or seem even remotely reasonable?
Eat Right for Your Type and these theories are not supported by scientific literature and the research has not been confirmed anywhere else. A little bit of time spent studying a biology book, or a human physiology text book, would dismiss the idea that blood type should specify dietary requirements.
Where Eat Right for Your Type gets really ridiculous, or downright dangerous for someone with severe weight problems, is that some blood types are told that they should not eat lean meats, or only vegetables, or can't eat certain vegetables, etc. Without knowing the individual and their fitness goals, how can anyone determine these requirements?
If you really need to lose some weight, go see your doctor, get to a gym, eat healthier, and don't go down the path of obsessing about secondary, if not irrelevent variables, like blood type. Success on these type of diets almost always comes from the fact they are highly restrictive in terms of what you can eat and how many calories you are allowed to consume. Any time you consider complicated, "science" diets, ask yourself a simple question: under all the filler and technical jargon, is the author simply manipulating you into eating less?