I know there are physical perks but are there psychological ones too?
I’ve done a long fast once. That fast changed me in a very spiritual way. I used to love gossipy things. Especially on radio or tv. When I stopped my fast it was an unexpected consequence. I could no longer stand to listen.
I’m currently fasting for psychological reasons, not spiritual. But I do that too. Fasting makes your head clearer and you’re less attached to unimportant things. Also, it detaches you from degenerate habits.
“Both basic and clinical investigations indicated that short-term calorie restriction might induce an antidepressant efficacy in depression, providing a novel avenue for treatment. Molecular basis underlying the antidepressant actions of calorie restriction might involve multiple physiological processes, primarily including orexin signaling activation, increased CREB phosphorylation and neurotrophic effects, release of endorphin and ketone production.”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4790398/
I think it heightens your sense of self control and can help you feel more confident in your ability to accomplish other tasks that you may otherwise consider difficult. Kind of like if you lift weights you might start walking around more confidently because you feel more physically capable.