Even during a lightweight fast of 24 hours (dinner to dinner), I have noticed that hunger manifests not as just a growling of the stomach or hunger pangs, but actual anxiety and panic. I had some experience with alternate day fasting a couple of years ago, and what I found was that once you got through the first fast, subsequent ones were much easier. I think what is going on there is that you have to, in a sense, prove to yourself that you aren't going to die from not eating for 24 or 36 hours. You are overriding your brain and your bodies intense desire to eat, even when it manifests as a deep feeling of dread and panic.
Consult with a fasting expert like Dr. Jason Fung, or your physician before taking on a fast.
