Macros is one of those words that gets thrown around constantly without anyone stopping to explain it, which is a shame, because the idea underneath it is genuinely simple and genuinely useful. This is a plain guide to what macros are and what the evidence actually says, so you finish holding a framework rather than a number you feel obliged to hit.
Macronutrients, or macros for short, are the three parts of food that give you energy: protein, carbohydrate and fat. Almost everything you eat is some mix of the three, and each one carries a different amount of energy per gram. Protein and carbohydrate each provide roughly four kilocalories per gram, while fat provides about nine, which are the standard Atwater values that sit behind the numbers on every food label.