During this response, cortisol
tells places of glucose storage (like the liver) to release glucose into the blood for energy.
Thus, all three groups were fed a high fat diet, which means that they used ketones
in place of glucose to some extent.
(In other, probably as complicated words: is full keto adaptation required for the body to burn ketones for energy
in place of glucose, in any significant capacity, or does this mechanism have partial effects even before fully propagated?)
Your body begins to transform fatty acids freed form your fat cells into ketone bodies, which can then be burned for fuel in
place of glucose (from carbs) by many of your bodies tissues.
The diet triggers a metabolic state called ketosis, in which the body begins to generate acetone and ketone bodies to use as alternative fuels in
place of glucose.