Macronutrients 101 — Protein, Carbs, and Fat
What macros are, how many calories each has, and how to split your daily intake for fat loss, muscle gain, or maintenance.
The big three
| Macro | Calories per gram | Primary role |
|---|---|---|
| Protein | 4 cal | Build and repair tissue |
| Carbohydrate | 4 cal | Primary fuel for exercise and brain |
| Fat | 9 cal | Hormone production, vitamin absorption, energy |
| (Alcohol) | 7 cal | No biological role — counts toward total |
Set protein first
Protein is the most important macro to nail. It has the highest thermic effect (~25% of calories burned digesting it), the highest satiety per calorie, and a direct effect on body composition. Use the protein calculator to set your daily grams, then convert to calories (g × 4).
Set fat second
Don’t go below ~0.6 g/kg/day of fat — that’s the minimum for healthy hormone production, especially testosterone and estrogen. Most people thrive on 0.8–1.2 g/kg fat.
Carbs fill the rest
Whatever calories remain after protein and fat are met → carbs. Carbs are not “bad” — they’re the most efficient fuel for moderate-to-high intensity training. Cut them only if you find a low-carb diet personally more satisfying.
A worked example
Goal: 2,000 cal/day, 70 kg body weight, training to build muscle.
Protein: 70 × 1.8 = 126 g → 504 cal
Fat: 70 × 1.0 = 70 g → 630 cal
Carbs: remainder = 866 cal → 217 g
Split: 126 P / 217 C / 70 F
Common macro splits
- Balanced — 30 / 40 / 30 (P/C/F)
- High-protein cut — 40 / 35 / 25
- Endurance / high-volume — 25 / 55 / 20
- Low-carb — 30 / 20 / 50
- Keto — 20 / 5 / 75
There’s no metabolic magic in any specific split — they only matter to the extent they help you hit your calorie and protein targets consistently.
Sources
- Atwater WO. Methods and results of investigations on the chemistry and economy of food. USDA Bulletin 21, 1895. (Origin of the 4/9/4 calorie values.)
- Pesta DH, Samuel VT. A high-protein diet for reducing body fat: mechanisms and possible caveats. Nutr Metab. 2014;11:53.