A better term than “physiological insulin resistance” is “glucose sparing.” It is a documented fact that people who have been ketotic well past the point of fat-adaptation generally see a modest rise in serum glucose, but without a corresponding rise in HbA1C. This appears to be perfectly normal and nothing to worry about. As already mentioned, it results from the fact that the muscle cells have fully adapted to metabolizing fatty acids and no longer need much glucose to fuel their activities, so they down-regulate their insulin receptors, apparently to spare the glucose the liver is producing for the cells that cannot do without it. Since gluconeogenesis is demand-driven, this rise in serum glucose is quite well-regulated and not a sign of incipient diabetes.
The late Dr. Joseph Kraft felt strongly that serum glucose was not a good measure of diabetes or even insulin resistance. His research strongly suggested that the pattern of the insulin response to ingesting glucose could indicate the beginnings of metabolic trouble as much as twenty years before serum glucose even begins to rise. Ivor Cummins and Dr. Gerber (among others) have done some presentations on Dr. Kraft’s data on YouTube (check the Fat Emperor and LCDU channels). The problem is that an oral glucose tolerance test is expensive and time-consuming, so it’s not likely to become the standard diagnostic test any time soon.
