I'm '0', and low carb suits me down to the ground. I don't have any problems with it at all.
I looked into this once (didn't do it 'cos he said no pork for Type O - as if hunter-gatherers didn't eat pigs!) and there is a certain amount of sense in the way he describes the change in diet - the archaeological record does show a shift in diet to cereal-based.
However, he doesn't say where he gets the evidence from for his theory of the historical development of blood types. I would say there are not enough bone samples from the Palaeolithic world-wide to give credence to his ideas - if indeed you can get blood type from a bone sample, which I don't know. Ethnographic parallels with modern hunter-gatherers aren't valid.
I believe there are some differences in blood type from continent to continent - unless I'm getting that confused with genetic distribution!
Viv 8)