One curious thing that happens in fasting is that the human brain switches from running on glucose as an energy source to running on ketone bodies.
"They know that the brain, an organ devoted to using glucose, can switch to use ketone bodies during prolonged starvation (2–3 days)" -- https://iubmb.onlinelibrary.wiley.com/d ... 9403304246
"Ketone bodies are three water-soluble molecules (acetoacetate, beta-hydroxybutyrate, and their spontaneous breakdown product, acetone) that are produced by the liver from fatty acids during periods of low food intake (fasting), carbohydrate restrictive diets, starvation, prolonged intense exercise, alcoholism or in untreated (or inadequately treated) type 1 diabetes mellitus." -- https://en.wikipedia.org/wiki/Ketone_bodies
"Bottom line: Ketone bodies are a cleaner, more efficient brain fuel that reduces oxidative stress, increasing mitochondrial activity, neuron signaling and cerebral blood flow — while naturally burning off fat reservoirs." -- https://www.honeycolony.com/article/ket ... -superman/
I heard experts saying (I don't have the links, sorry) that the brain of a chimpanzee can't use ketone bodies the same way the human brain can. And one expert gave an elaborate answer about how the human brain has evolved differently than the brains of primates. There was something about that explanation I found missing. Why wouldn't for example chimpanzees have evolved to be able to fully use ketone bodies to fuel their brains?
Could be something spiritual!
"Carrying body and soul
and embracing the one,
can you avoid separation?
Can you let your body become
as supple as a newborn child’s?
In the opening and shutting of heaven’s gate,
can you play the feminine part?" -- Tao Te Ching, verse 10 https://www.modernagespirituality.com/t ... -verse-10/
And it says in the Bible that we can't live on food alone, and we need to be reborn out of water [fasting
] and Spirit [mindfulness + the Holy Spirit].