I made an article myself called Human Biological Clock n Intermitt fasting. Its an article discussing how our bodies work with nature and the hormone cortisole, wich is another reason to fast in the morning hours. Nevertheless, rethink your question and ask your self...
How can people workout and gain muscle while fasting, arent they tired and just out of juice? well, if our bodies simply became tired and our motivation just fell apart, woudent we just die as a race? Now the human body actually activates some hormones that makes us fight, fight to find food and fight to kill... Thats why some people fell energized when fasting, some become stronger, other suddenly think clear. I think intermitt fasting is a great tool, and i think alot of people dont think way back in time, and try to understand how the human body actually works.