I love how refreshed I feel by eating right.

Food's feedback arrives late, which is most of the problem. Lunch shows up at three in the afternoon, hours after any decision was made, and by then the slump feels like a fact about the day rather than a result of it.

Occasionally the loop closes and you catch it. A week of decent meals, and the four o'clock fog simply does not arrive, and you notice its absence with genuine surprise.

That noticing is worth more than any rule. It is the only argument the body makes on its own behalf, and it only speaks in retrospect.