Also, he's weirdly obsessed with digestion for some reason.

From what I understand of his themes, he wants to move away from the brain (pure intellect, science, philosophies that come as a result of rational thought and natural conclusions of "The Good") to philosophies born of instinct and what "feels right". You don't really want certain foods because you came to the natural conclusions that it is the healthiest for you by reading the ingredients and comparing it to your dietary needs, you want food because you tried it and you like the way it makes you feel. He essentially wants to treat morality the same way, adopting whatever morality system affirms his life the most.

Nietzsche was a sickly guy, and when he was feeling bad, he was stuck in bed, feeling sick and being resentful of himself and everyone. When he was feeling good, he would go on long walks and imagining an ideal person who was untethered by modern morality. I kinda see these as depressive and manic phases (not to diagnose him, it's just the closest parallel to my own life), but he saw the true emotions/drives behind slave and master moralities