DoreenT:
blood type O is also called "thrifty " genotype.
Since it's the most ancient blood type, they suppose to store fat in order to survive famine, and will be the last one to die in case of it. but also because of this strong fat storing genes, ppl with this genotype have higher level of insulin and can become IR if not careful with the carbs . I'm not sure if it's that simple bu I'm type O+, and I laways had to be careful with bread and potatoes in order to control my weight.

I'm not sure if this is true, there are very slim and healthy ppl who either are vegeterians or live on a high carbs/low fat diet and feel fine on it. my DH is type A and even he's not a vegeterian he can't live without carbs like fruit and whole grains. He's not a big meat eater either. He can eat oatmeal with low fat milk for BF not be hungry for hours.
I can live without grain and don't feel deprived as long as i have some sort of animal protein preferably with fat, vegetables and some fruit for desert. I also know other type A who are slim and thrive on cereals, fat free yougurt and bananas. I'll be miserable and hungry all the time on this diet. I browsed the Metabolic Typing Diet book by William Linz Wolcott. This book was highly recommended by Dr.Mercola. The basic concept is that everyone is metabolically unique and one man's meat is another man's poison. This is link to a Dr.Mercola site on this diethttp://www.mercola.com/2003/feb/26/metabolic_typing.htm in case anyone is interested. The book didn't impressed me because for a mixed type it's hard to calculate your nutriotional requirements.
I'm not sure if it's the blood type or anything else but the concept makes sense to me.
Regards,
Dina