Macronutrients are the building blocks of any diet—proteins, carbohydrates, and fats—and they are where all of your calories come from (minus alcohol, which contains calories but is technically a toxin, so we don’t count it as a macronutrient). Macronutrients supply the energy, fuel, and nutrients you need to live. Each macronutrient serves a specific purpose and should be consumed in the proper amount for optimal health. Quite a few variables come into play when setting up macronutrient ratios, but first, you must understand what they are, what they do, and what foods they come from.