Fat loss is a calorie problem. Macros — protein, carbs, and fat — are how you spend those calories in a way that keeps you full, protects muscle, and doesn’t wreck your energy. The good news: once you know your TDEE, the math takes about two minutes.
Start from your calorie target
Macros are downstream of calories. Before you split anything, know your TDEE — the number of calories you burn in a normal day — and subtract a deficit. A sustainable cut is 15–20% below TDEE, which typically lands you at 300–500 calories a day under maintenance and produces 0.5–1 lb of fat loss per week.
Don’t chase aggressive deficits. Cutting 1,000 calories a day sounds fast on paper, but it torches lean muscle, crushes training performance, and almost always ends in a binge. Slow is reliable. Reliable is the whole game.
Set protein first
Protein is the one macro worth obsessing over in a deficit. It builds and preserves muscle, it blunts hunger more than fat or carbs, and it has the highest thermic effect — your body burns about 25% of protein calories just digesting it.
- 0.7 g per lb bodyweight — minimum floor for fat loss while protecting lean mass.
- 0.8–1.0 g per lb bodyweight — the sweet spot for most lifters in a deficit.
- 1.0+ g per lb bodyweight — diminishing returns. Fine if you prefer it, not required.
A 180 lb adult at 0.9 g/lb = 162 g of protein per day. At 4 cal/g, that’s 648 calories committed to protein before anything else moves.
Enter your TDEE and goal. Out come your P/C/F grams per day, with the math shown.
Set fat next
After protein, fat gets a floor — not a ceiling. Dietary fat handles hormone production, vitamin absorption, and satiety. Going too low (below about 0.25 g per lb of bodyweight) tends to tank both mood and training output.
- 0.3–0.4 g per lb — typical range for a balanced cut.
- 0.4–0.5 g per lb — higher-fat preference, works well if you’re doing lower-carb.
- 0.25 g per lb — the practical floor. Don’t go below unless you’re bodybuilding peak-week.
For the same 180 lb person at 0.35 g/lb = 63 g of fat per day. At 9 cal/g, that’s 567 calories.
Let carbs fill the rest
Carbs are the flex variable. Once protein and fat are set, subtract their calories from your target intake, then divide the remainder by 4 (cal/g) to get your carb grams. If our 180 lb person is eating 2,200 calories for fat loss:
- Protein: 162 g × 4 = 648 cal
- Fat: 63 g × 9 = 567 cal
- Remaining: 2,200 − 648 − 567 = 985 cal for carbs
- Carbs: 985 ÷ 4 = 246 g per day
That’s a balanced split — roughly 30% protein, 26% fat, 45% carbs. Shift the fat-carb balance based on what keeps you full and training well. There’s no magic ratio; there’s just the ratio you can actually follow.
Track, measure, adjust
Macros without a scale are wishful thinking. Weigh your food for the first two weeks to calibrate your eye — you only need to do it once. Track calories daily, protein daily, and let fat/carbs float within reason.
Check the scale weekly, not daily. Expect 0.5–1 lb of loss per week on average. If two weeks pass with no change, recalculate TDEE (a smaller body burns less), drop calories by about 10%, and hold protein constant. Don’t cut protein to make room for more carbs — you’ll regret it at the mirror.
Weight, calorie target, goal. Done. Share the URL with anyone who asks how you do it.