One more argument in favor of allowing fat metabolism is in how insulin works to help regulate our use of the pathways to producing energy -sugar and fat metabolism. It was, and is, never about a choice of sugar metabolism or fat metabolism. It really is about using both sugar and fat metabolism.
As I see it, insulin is a stress hormone. By Ray Peat's definition, a hormone is considered a stress hormone when more of it is produced under stress. The less stress hormone is produced and present, the better it is and the more healthy the body.
It is only produced when the blood sugar level is too high. And the blood sugar level is too high when the body tissues cannot absorb and metabolize sugar fast enough because there is a pathogenic blockage in the chain of reactions involved in mitochondrial respiration involving sugar. It is like when a river floods because the land surrounding the river is unable to take in the water from the river due to a mismanaged ecosystem.
When the body is metabolically healthy, insulin is not needed. When insulin is not present, blood sugar will not convert to fat in the liver.
Lipolysis will naturally occur as well, as it is when there is insulin when lipolysis is inhibited. What this means is that in a healthy metabolic state, the body defaults to allowing both sugar and fat metabolism to simultaneously take place.
That is the natural order. There is nothing wrong with fat metabolism going hand in hand with sugar metabolism. It should be allowed.
But note that this takes nothing away from the idea that healthy mitochondrial metabolism is still highly dependent on using sugar as a substrate, more so than in using fat as a substrate.
