Macronutrients, or macros for short, are the nutrients that provide your body with energy: protein, carbohydrates and fat. Alcohol also provides energy but does not count as a nutrient. Together, your macros determine how many calories you eat.
How much energy they provide
According to the Atwater system, these are the standard values per gram: protein 4 kcal, carbohydrates 4 kcal, fat 9 kcal, alcohol 7 kcal. Fiber is counted at 2 kcal.
The order to set them in
Calories decide whether you gain or lose. Macros help decide what you build or keep. This order works well:
- Protein first, based on body weight; 1.6 to 2.2 g per kg is typical.
- Fat as a share of calories; 20 to 35 percent is typical.
- The rest goes to carbohydrates.
Example: At 80 kg and 2,600 kcal, 2.0 g of protein per kg is 160 g, or 640 kcal. 25 percent fat is 650 kcal, or about 72 g. That leaves 2,600 - 640 - 650 = 1,310 kcal for carbohydrates, about 328 g. These numbers are a worked example.
How precisely you need to hit them
What matters is calories and enough protein on a weekly average. Small deviations in fat and carbs hardly matter, and you can shift both based on preference and fullness, as long as fat does not stay very low for long. When you change your calorie target, for example when moving from a bulk to a cut, mostly the carbohydrates change. Protein stays high in both phases.