The two aspects I mentioned – psychological traits – arise from the reflection on the body's initial reactions to the physiological changes. What I mean in particular is, feelings of hunger only are experienced for the first few days before the body begins to adapt. Reflection on that change leads to a better awareness of one's resilience. Feelings of tiredness or limitedness also fade away, leading to a reflection that spurs empathy with those less fortunate or who are otherwise excluded from our high-speed, overeating economy and society.
Ultimately – fasting is physiological/metabolic meditation, similar to how commonly understood meditation is psychologically/emotionally beneficial.
I hope that helps! 🙂