Little Turtle, you mentioned a conversation between a diabetes specialist and a neurologist. With reference to neurology, fasting can stimulate a process of "neuronal autophagy" where the cells "recycle" bad bits of themselves (especially proteins). That's a salutary, therapeutic process provided the fast continues long enough but not too long.

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Eventually these paths return me to the question of what can I reasonably do to make the ground of my life less fertile for depression and anxiety. I'm still searching.