Dr. Peter D'Adamo is a naturopathic physician who has written a couple of books about the idea that your blood type is somehow related to what type of diet you should be eating.
Dr. Adamo, as a fellow bullshit artist, I would like to commend you on your ability to link two seemingly simple, yet completely unrelated items into one diet plan. It is almost as if you opened a medical dictionary at random and found the term blood type, then opened it again and found the term weight loss, and linked them together. Brilliant.
Apparently, simplicity is a hallmark of your plan because only the blood type has any effect (A, B, AB, O), other identifiers (like positive, negative) have no effect.
Well, without further gibberish here is how you can eat right for your blood type:
Type O: Eat a high protein diet.
Type A: Eat a diet high in vegetables and free of red meat.
Type B: You will do well to consume a lot of dairy.
Type AB: Eat a diet high in vegetables and dairy.
I am so inspired by this work, that I have decided to come up with my own blood type diet. Here is the FadDiet.com version of the blood type diet:
Type O: Exercise a lot.
Type A: Don't eat so much.
Type B: Exercise more, eat less.
Type AB: Eat less, exercise more.
There you go. I should write a book.