Nutrition · foundations
The three macronutrients supply all of your energy and most of your body's raw materials. Here is what each one does and roughly how much you need.
Protein provides amino acids for muscle, enzymes, hormones, and immune molecules, and yields 4 kcal per gram. General health needs are around 0.8 g per kg of body weight; active people and those building or preserving muscle benefit from 1.2–1.6 g/kg or more. Protein is also the most satiating macronutrient.
Carbohydrates are the body's preferred quick energy, at 4 kcal per gram, and the main fuel for the brain and hard exercise. Quality matters more than quantity: whole grains, legumes, fruit, and vegetables bring fiber that slows absorption and steadies blood sugar, unlike refined sugars and starches.
Dietary fat carries fat-soluble vitamins, builds cell membranes, and makes hormones, at 9 kcal per gram. Favor unsaturated fats from fish, nuts, seeds, and olive oil; keep saturated fat moderate and avoid industrial trans fats. A common target is roughly 25–35% of calories from fat.