I heard a lady say that having the bloodtype of O postive there is a certain way food reacts to you and you produce more acids in your stomach for breaking down beef in particular, but it doesn't work well on porks...
I found that quite interesting since I share the same bloodtype.. and I'm packing an extra 20 lbs...so who knows of this that can help me slim up for summer.. where are some supporting links or facts on what my bloodtype should and shouldn't consider for my diet?
I have to say.. I've NEVER heard of this before..and if it's a fact then why isn't THIS taught in elementary school other than just the basic food pyramid?

In human evolution, everyone started out as Blood Type "O", the original Hunter/Gatherers, out of Africa, living off of natural foods found in the wild: meats, fish, nuts, fruits, eggs & honey...Still 50% of humans today have this Type...
The first farming societies, which came about around the time of the last Ice Age (12,000 years ago) gave rise to the first surviving mutation, Blood Type "A". This Blood Type was compatible with the ingesting of cereal grains, cultivated vegetables, as well as poultry, some pork & fish. They comprise appx.30% of the human population today...
The first nomadic people, who traveled on, and with livestock, including, camels, horses, oxen, sheep & goats, learned to milk their transportion, and the second mutation "B" emerged. This is the only type that dairy products are truly compatible with...About 15% of the population has this Type today...
Finally, "A" & "B" which are both dominant over the original "O" made a compromise on the genetic level, and created the newest Blood Type "AB". This Type is only 1000 years old, has some characteristics as "A" & "B", and makes up less than 5% of the Types of the world...

There's a book on this, it's called Eat Right for Your Type. Basically the author says that different blood types came from different parts of the world with different diets and you should follow the diet of those original people with that blood type.
I know some people who've lost weight and swear by it and others who hated it (like me). I used to go to a nautropath and she put everyone on that diet right away. It restricts foods like bell peppers and tomatoes which no other diet (except maybe Atkins) says are "bad" for you.

I doubt it is true, but hundreds of thousands of people have bought the books about blood-type diets... but funnily enough, hundreds of thousands of people haven't magically lost weight.