Metabolic Typing (MT) sounds like it may have some merit, but I wonder about the boundaries placed on the spectrum to keep people within functional, healthy ranges. I am concerned that MT may accommodate less-than-ideal macronutrient intakes for those on the extremes, but claim to feel better out there. Might a "protein type" drive their body too acidic? Might a "carb type" just be hanging onto their typical treatment for symptoms of hypoglycemia? How do you get a carb type adapted to burn fat again if they have eaten lots of bread and pasta for years? Would Mr. Marlowe agree that the individual might benefit from going ketogenic for a period of time to ramp back up their fat-burning machinery?
