The Metabolic Typing Diet
Summary: The Metabolic Typing Diet recommends finding the optimal carbohydrate, protein, and fat intake for one's "metabolic type" based on a detailed survey and empirical results of the diet.
The Metabolic Typing Diet is explained in the book of the same name, and Dr. Mercola is a major proponent. The book contains a detailed survey which supposedly helps to determine one's type based on questions like "How do you feel about potatoes?" and "Do you have a lot of energy after eating meat?" I have not talked to anyone whose "metabolic type" based on the survey was other than "Mixed Type" so don't find the survey very helpful.
The Metabolic diet is primarily concerned with keeping blood sugar levels low, just as in Atkin's and The Zone. It is helpful in that, unlike these one-size-fits-all diets, one is instructed to find the percent of carbs, proteins, and fats that allows one's blood sugar to stay low. This can be higher than allowed on the Zone's strict 40-30-30 (carb/protein/fat) regimen and especially Atkin's. It might be 60/25/15 for a pure "carbo type" or 50/30/20 for a "mixed type." This makes the diet easier to follow and perhaps more effective for people whose blood sugar is already well regulated and does not spike that high from eating carbs or by those who have less a protein or fat requirement.
After the metabolic type is determined based on the survey, one is instructed to follow a diet with limited carbs, then start raising the carb intake until the ideal ratio is determined as evidenced by the best energy levels, digestion, and well-being. If the diet is seemingly not producing benefit it then instructs one to follow Eat Right 4 Your Type - it even includes an abbreviated version of the ER4YT food lists.
All in all, I find this diet not very helpful and The Zone and ER4YT more important. I think it is better to follow the Zone, while taking ER4YT into consideration, for two to four weeks. If at this point the benefit is not apparent, raise carb and lower fat and protein intake gradually until the best ratio is found.