I have always thought the largest fruits of fasting are the mental ones. The primary focus on most fasting talk is the physical effects. Things like it gives your body a chance to clean house, it is freed up to do other work that needed to happen; when you give the digestive system a rest it gets a needed rest, etc.
For me the biggest experience is the powerful realization that you are in the driver seat. You get to choose. Not only do you not have to eat compulsively you can choose not to eat at all. You didn’t eat and the whole world did not fall apart. That is empowering and freeing to know that you have this ability. It frees you from your hooks and rules: ie, I have to eat every 3 hours or I will die. And the panic that ensues if that doesn’t happen.
It is like learning to fall and roll properly in Aikido. After practicing and knowing you fall well, just standing there becomes a different experience. Walking is different.
When you become familiar with yourself as someone who can choose when to eat (say within a range of 24 hours) it increases your familiarity with yourself as someone who can also choose what you eat regardless of impluses or pressures or time of day or habits or routines or place and time. You get to choose.
Leaving your daily habit of eating is like leaving the country. When you get out you look back with a different view. That is refreshing.
It also provides the opportunity to engage and, however briefly, overcome one of our greatest fears: You might starve to death!
There are a series of feelings that one experiences when fasting.
During a fast you feel hungry then as you wait you discover the hunger goes away. It is puzzling, hey where did that hunger go? It was just here like an angry lion sitting in the middle of the dinner table. It was just here. Is it gone? You will notice it go. And depending on the nature of your fast you may see it come again and go again many times. It is a great experience to see you could be hungry, not eat, and then not be hungry. It is a physiological self discovery. This is what happens with feelings and emotions. We get so attached to them, we are so angry, or so happy, or so scared and then we can notice eventually the feeling just goes away. Emotions and feelings (even the feeling of hunger) are like passing clouds.
When you come back to eating you arrive a more enlightened being.