What macros are and why the split matters
Macronutrients are the three things that supply energy: protein, carbohydrate and fat. Total calories determine whether you gain or lose weight; the split between macros determines what you gain or lose, and how you feel doing it.
| Macro | kcal per gram | Primary role |
|---|---|---|
| Protein | 4 | Muscle repair and growth; the most satiating macro |
| Carbohydrate | 4 | Primary fuel for high-intensity work |
| Fat | 9 | Hormone production, vitamin absorption, cell structure |
| Alcohol | 7 | No nutritional role; counts toward calories |
Protein is the one worth getting right first. It is the most satiating per calorie, has the highest thermic effect — 20 to 30% of its calories are burned digesting it — and it is what protects muscle when you are in a deficit.
The common splits
| Approach | Protein | Carbs | Fat | Suits |
|---|---|---|---|---|
| Balanced | 30% | 40% | 30% | Most people, most goals |
| High protein | 40% | 35% | 25% | Fat loss while preserving muscle |
| Low carb | 35% | 20% | 45% | Appetite control, insulin sensitivity |
| Ketogenic | 25% | 5% | 70% | Therapeutic use; requires commitment |
The evidence on split is less dramatic than the internet suggests. Controlled trials that match calories and protein find little difference in fat loss between low-carb and low-fat approaches. What matters is which one you can actually sustain.
Protein targets by activity
| Situation | g per kg |
|---|---|
| Sedentary adult (minimum) | 0.8 |
| General health and activity | 1.2 – 1.6 |
| Resistance training | 1.6 – 2.2 |
| Fat loss while training | 2.0 – 2.4 |
| Older adults (sarcopenia prevention) | 1.2 – 1.6 |
Making it work day to day
- Spread protein across meals. Roughly 0.4 g per kg per meal across four meals maximises muscle protein synthesis better than loading it into one.
- Weigh food for two weeks. Portion estimates are typically 20 to 40% low. You only need to do this once to recalibrate your eye.
- Hit protein and calories; treat the rest as flexible. Carb and fat can shift day to day with little consequence, provided fat does not drop below about 0.6 g per kg.
- Fibre is not on this list but matters. Aim for 14 g per 1,000 calories — around 25 to 38 g a day.
For the calorie target itself, see the calorie calculator and the TDEE calculator.
Frequently asked questions
How much protein do I need?
For general health, 1.2 to 1.6 g per kg of body weight. If you train with weights, 1.6 to 2.2 g per kg. If you are losing weight while training, the upper end protects muscle better.
A 75 kg person training regularly needs roughly 120 to 165 g a day.
Do macros matter more than calories?
No. Calories determine weight change; macros influence body composition, satiety and performance. You cannot out-macro a calorie surplus.
That said, protein is the exception worth prioritising — it changes how much of any loss comes from muscle rather than fat.
What is the best macro split for fat loss?
A higher-protein split — around 35 to 40% of calories — with the remainder divided by preference. Higher protein preserves muscle in a deficit and keeps you fuller.
Beyond protein, the carb-versus-fat split makes little measurable difference when calories and protein are matched.
How accurate do I need to be?
Within about 5 to 10 g of your protein target and 100 kcal of your calorie target is plenty. Chasing exact numbers daily adds stress without adding results.
Consistency across a week matters far more than precision on any single day.