Fasting is a great way of encouraging autophagy and keeping your insulin levels low. Contrary to what some people think, fasting will quicken your metabolism, making you burn more stored fat and also saving muscle.
In the paleolithic starvation was common, and your body didn't just shut down due to lack of food. On the contrary, the fasting state increases our mental focus and our physical readiness, so we can go out there and hunt.
In my opinion, fasting is a physiological state, we have just grown accustomed to eating ALL THE TIME.
GENESIS