What it does, how much, and which ones. Nothing here is banned. It's a dial with three settings: more, some, less.
It's what muscle is built and repaired from, and it's the part of a meal that keeps you full. You can feel when it's off.
Measured in palms: a piece the size and thickness of your own palm.
Fresh, lean and close to how it started goes on the left. The more that's been done to it, the further right it sits.
Lentils and beans count as your protein if you don't eat meat; otherwise treat them as carbs. Red meat is in the green column, with a common guideline of about four palms a week.
Four quick tests. The last one matters as much as the first three.
Find where your usual choice sits, then move it one notch. Do that most days and you're done.
Pick one.