This diet is going to work primarily on dividing different individuals by their blood groups. The main blood groups are type A, type B, type AB and type O. Once you know which of these blood groups you belong too, then you can go about determining a diet that you should follow. Furthermore, each type is classified as a certain type of eating 'style'.
Type O would be classified as meat eaters and should focus more of their intake around protein rich foods, while keeping carbohydrates to a minimum. Vegetables and fruit can still be consumed in abundance however as they are generally lower in carbohydrates to begin with.
Next up, type A's are the vegetarians. They should consume mostly vegetables, seafood and tofu. Meat does not react well with their system and will only cause stomach upset and difficulty maintaining feelings of wellness.
Type B's on the other hand are balance omnivore's and do best eating all meat except chicken, then also consuming plenty of dairy, grains, beans, vegetables and fruit. The one thing these individuals need to really watch out for is wheat and wheat products.
A mixed diet in moderation is what's called for for the type AB's as they seem to react fairly well to most food, although should be slightly wary of consuming too much red meat.
So if you don't already know which type you fall into, be sure to get a test done today and then you can start making changes to your diet and see the results you're looking for.