Health⏱ 6 min read
How to Calculate Macros for Weight Loss: Protein, Carbs, and Fat
Calorie counting alone ignores protein — and without enough protein on a deficit, you lose muscle as well as fat. Here is how to set protein first, then distribute remaining calories across carbs and fat.
The most common mistake in weight loss nutrition is prioritising overall calorie restriction without protecting protein intake. The result is losing muscle alongside fat — reducing metabolism and leading to the "skinny fat" outcome most people want to avoid.
Step 1: Calculate Your Calorie Target
Start with TDEE (Total Daily Energy Expenditure):
Use the Mifflin-St Jeor formula x activity multiplier.
Example: 35-year-old woman, 75kg, 165cm, lightly active
BMR = (10 x 75) + (6.25 x 165) - (5 x 35) - 161 = 1,489 kcal
TDEE = 1,489 x 1.375 (lightly active) = 2,047 kcal
Calorie deficit for fat loss:
Moderate deficit (-500 kcal/day): 2,047 - 500 = 1,547 kcal target
This produces approximately 0.45 kg/week fat loss
Step 2: Set Protein First
In a calorie deficit, protein needs INCREASE to preserve muscle.
Target: 1.8-2.4 g/kg of body weight (higher end for larger deficits)
At 75kg with moderate deficit (2.0 g/kg):
Protein: 75 x 2.0 = 150g/day
Protein calories: 150 x 4 = 600 kcal
This is the non-negotiable foundation.
If you hit 150g protein, the specific carb/fat split matters far less.
Step 3: Set Fat (Minimum)
Dietary fat is essential for hormone production and fat-soluble vitamins.
Minimum: 0.5g per kg of body weight (lower limit for hormonal health)
Recommended: 0.8-1.0g per kg
At 75kg: 60-75g fat/day
Fat calories: 70g x 9 = 630 kcal
Step 4: Fill Remaining Calories with Carbohydrates
Remaining calories = Total calories - Protein calories - Fat calories
1,547 total - 600 (protein) - 630 (fat) = 317 kcal from carbs
Carbohydrate grams: 317 / 4 = 79g carbs/day
Final macro split:
Protein: 150g (39% of calories)
Fat: 70g (41% of calories)
Carbs: 79g (20% of calories)
Total: 1,547 kcal ✓
This is a high-protein, moderate-fat, low-carb approach —
appropriate for fat loss while preserving muscle.
Low carb is not required; adjust fat/carb ratio to preference.
Adjusting for Training
On training days, increase carbohydrates (not protein or fat):
Training day: add 30-50g carbs (120-200 kcal)
Rest day: stick to base target
This fuels performance without excess calories on non-training days.
Pre-workout meal (2hr before): prioritise carbs for training fuel
Post-workout meal (within 2hr): protein + carbs for recovery
Protein timing matters less than total daily intake:
Meeting 150g/day consistently matters more than timing
(Post-workout protein spike is beneficial but not magical)