Thank you, I have to look up fasting. We are not taught about autophagy in medical school. We are not taught anything about anthropology, and only very little about biochemistry (so nothing about nutrition specifically).

The Randle cycle is a biochemical concept. If you consume more carbs than fat, than your cells will spend more glucose and stimulate the uptake of glucose. If you consume more fat, then your cells will oxidize fat and inhibit glucose entry and expense. It's why the worst thing to do to your body is eat a fatty and carb rich meal (=junk food). Similarly, it seems to me that ketosis, i.e. fat adaptation is best for fasting, since you will be oxidizing your body's fat excess fat supply. That's just an opinion however.