Macronutrients 101 — Protein, Carbs, and Fat

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.

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. If you’re new to splitting macros, a dedicated macro tracker makes the daily allocation much easier than mental math.

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.