Fat-adaptation and keto-adaptation seem similar -- I hear some people use them interchangeably. But I thought they involved completely different energy substrates (your mitochondria are oxidizing fatty acids vs. ketones, right?)
Are the two states related to one another biochemically? Do they share any upstream processes in terms of insulin response, blood sugar regulation, etc? Or are they completely different and it just happens that you get into them in the same way (eat lots of fat and limit carbs)?
My more practical question is whether they're partially exclusive:
If you're extensively fat-adapted, does that make it harder to get into ketosis because your body can hoard its carbohydrates more effectively?
If you're running on ketones, does that hinder fat adaptation because your cells have an energy source other than fat?
Or do people who are eating a low-carb, high-fat diet tend to mix mitochondrial oxidation of fats and ketones without any real problems?
As a partial answer, you do not have to be keto adapted to be fat adapted. It is easy to be fat adapted while maintaining an adequate carb intake amount to stay out of ketosis. In fact, fat burns through the krebs cycle the most efficiently in the presence of some glycogen, or glucose. Whereas only under strict carb restriction, and when there is not adequate glucose for the brain, will the liver begin to make ketones. Also, when you are in ketosis, your body is still getting the majority of its energy from fat metabolism, not ketone metabolism.