Following up from the question Are carbohydrates an essential component of human diet? I am interested in knowing more specifically how carbohydrates, fats and proteins are linked in the mammalian diet.
For example, cats and other obligate carnivores eat mostly protein, so I imagine that protein has to be converted first to fat and then to glucose and other carbohydrates that the body needs. Does that mean cats are in a state of ketosis constantly? Do cats have special metabolic tuning to optimize on this metabolic pathway?
Human variations seem to suggest that such tuning exists. For example, (historic) eskimoes when fed carbohydrates tend to be especially likely to suffer from obesity and diabetes. This would suggest that their bodies are tuned to exist on protein and fat. What is this tuning?