Like ColbyJax, I lost a fair amount of weight in a short time without too much effort, and wondered why I had done so well on this diet, when I'd failed at other attempts at healthy eating.

I examined the blood type dietary theory, and although some people's results I've checked on correspond to theory, some don't. I think there's a stronger connection between diet and one's metabolic type. I've visited the clinic of one of the published practitioners, and talked to about 20 clients in attendance at an open house at the clinic. Granted, this is going to a biased population, but I was impressed by the degree of positive results achieved by their dietary modifications, especially considering the states that some of the clients started with (they included both type I and II diabetics, and cancer patients).

Also in its favor is the fact that this dietary model has a thirty-year history, whereas the blood-type model is less than a decade old. In addition, the metabolic typing model relies on a battery of lab tests to determine an initial dietary plan, then requires follow-ups with a clinician to monitor one's reaction and make appropriate adjustments. I think that this is a sounder approach than relying strictly on a single aspect of one's biology.

There are a couple of books available on this subject. Having read both, I recommend Kristal and Haig's work for its readability and emphasis on lab work to determine one's metabolic type. Wolcott's questionnaire-based method can be useful, if you clearly fall on one end of the metabolic typing spectrum or the other.