How your macros are set
First we estimate your maintenance calories (TDEE) with the Mifflin-St Jeor equation and your activity level, then adjust for your goal (about −20% to lose fat, +12% to build muscle). The calories are split into the three macronutrients:
- Protein: ~2 g per kg of body weight — protects muscle and keeps you full.
- Fat: ~25% of calories — supports hormones (each gram = 9 calories).
- Carbs: the remaining calories (each gram = 4 calories) — fuel for training.
Worked example: a 75 kg moderately active man maintaining weight at ~2,600 kcal would get roughly 150 g protein (600 kcal), 72 g fat (650 kcal), and the remaining ~1,350 kcal — about 338 g — as carbs.
Where these targets come from
The protein range used here sits within guidance from sports nutrition bodies such as the International Society of Sports Nutrition, which recommend roughly 1.6–2.2 g/kg for people actively training. The 25% fat share and "carbs fill the rest" split are common practical defaults in dietetics rather than a single named formula — reasonable starting ratios to adjust from, not a fixed biological requirement.
Why protein comes first
Protein is the macro most worth getting right. It preserves lean muscle in a deficit, supports growth in a surplus, and is the most satiating — making any calorie target easier to stick to. Spread it across 3–4 meals.
Make it practical
You don't need perfection. Hit your protein target, keep fat and carbs roughly in range, and judge progress over 2–3 weeks. Adjust calories if the scale isn't moving as expected.