Blood-type diet

This is what I heard from a Swiss guy. He was once asked by his Japanese girl friend, who he said was sexy for a Japanese girl by the way, what his blood type was. Since he did not know his blood type, he answered he had no idea. Surprised, she said
"It is quite strange of you not to know your blood type."
"But I am afraid most of the people are like me and do not care about their blood types."
She said.
"I wonder how Swiss people know other people's personality."
Even if this lovably stupid girl might be an extreme, the blood-type-personality-telling is thus popular among the Japanese. Since then he has been interested in blood types, partly for fear of being dumped by his slightly boneheaded girlfriend.
He told me "you would think that this is only Japanese thing. But actually it's not. In the US, there is a theory called blood type diet."
"Blood-type diet?" I repeated, curious.
"The theory goes that people should eat foods suitable for their blood types. If they don't they will get ill or in worst cases, die. For example, the people with blood type O are born carnivorous because they have genes of hunters. So they must eat meat. It is very alarming for Type O people to be a vegetarian. People with A type blood on the other hand, are agricultural species and therefore herbivorous. So they must eat only vegetables."
Well, I thought it was more or less like blood type personality analysis. The Japanese do not know anything about this fishy diet and enjoy a longer life span than US people. But what it interested me more was the theory's back ground.
The type O people are born hunters. Then they must have leaderships and self-confidence. They must be independent. They don't like planning but have capabilities to respond to changes. Aren't these exactly defined for O type in the blood-type-personality analysis?
Type A are farmers. Then they have to be organized and punctual because they must obey the calendar of the seasons and nature's schedule of growing crops. They have to be cautious and discreet.
Don't they check with each other? Maybe this is just a coincidence but a beautiful coincidence, maybe beautiful enough for an anthropologist to start smelling a scent of truth.
So how about the Type B? It is somewhere between O and A. They are omnivorous; eat meat and vegetables. In short, they can eat anything they like. That may be why they go their own way. Doesn't this justify my trait of being messy?