Happiness comes through staying hungry. Is that so? Let's go through it.

The happiness that generates within us can be the product of several factors.

Well, one of these factors might be the ones coming from biochemical processes.

For instance, the dynamics within the signal transduction of insulin hormone on one hand.

On the other hand, the action of glucagon activity when the body gets in need of food supply “internally”. Since long-term fasting is the process of getting & staying hungry for a long period of time (> 15 hrs).

At some point, the dynamics of insulin and the activity of glucagon can be compared as carbo-diet vs. keto-diet.

When the concentration of insulin vs. glucagon shifts periodically. I guess some people also experience a sense of happiness when they give up carbo-diet over keto-diet. Interesting, happiness doesn't like things as i) food overload, ii) mental overload, and iii), etc.

More than that fasting is all about cell suicide thing from the view of molecular biology. It's all about autophagy. It's the one who honored Prof. Yoshinori Ohsumi's 2013 Nobel Prize in Physiology.

In the time-lapse of long term fasting (staying hungry), the autophagy, toxic substances are killed through a programmed schedule.

These are all scientific points.

Well, there're of course lots of molecular mechanisms behind long-term fasting [ > 12 hrs].

Just one thing to say is that fasting is commitment!

It's the commitment to One who's programmed and still maintains all these dynamics.

I guess you feel a sense of happiness since you've entered the phase of that One at the spiritual level, leaving behind the physical dimensions.