Calories determine whether you gain or lose weight. Macronutrients (protein, carbohydrate and fat) strongly influence what you gain or lose, how you feel and how well you train. There is no single perfect macro split, but the research points to clear priorities: set protein first, give fat a healthy floor, and let carbohydrates fill the rest according to your activity and preferences. This guide explains how to do that for each of the three main goals.
Macro basics: calories per gram
| Macronutrient | kcal per gram | Main roles |
|---|---|---|
| Protein | 4 | Muscle repair and growth, enzymes, satiety |
| Carbohydrate | 4 | Primary fuel for high-intensity training, brain fuel, fibre |
| Fat | 9 | Hormone production, vitamin absorption, cell membranes |
| Alcohol (not a macro) | 7 | No essential role; easy to over-consume calories |
To turn a calorie target into grams, multiply the calories by the percentage for each macro, then divide by the kcal per gram. For example, 30% protein of 2,000 kcal = 600 kcal ÷ 4 = 150 g protein. Our macro calculator does this automatically from your TDEE.
The priority order: protein, fat, then carbs
1. Protein
Protein is the macro with the strongest evidence for body composition. The meta-analysis by Morton and colleagues found that protein intakes up to about 1.6 g/kg/day maximised gains in muscle mass from resistance training, with some individuals benefiting up to 2.2 g/kg [1]. The International Society of Sports Nutrition recommends 1.4–2.0 g/kg/day for most exercising individuals, and higher intakes (2.3–3.1 g/kg of lean mass) during energy restriction [2].
2. Fat
Dietary fat supports hormone production, including testosterone and oestrogen, and absorption of vitamins A, D, E and K. Most guidelines suggest keeping fat at least 20–25% of calories, or roughly 0.5–1.0 g/kg of body weight. Very low fat intakes for long periods may impair hormonal health and make diets less enjoyable.
3. Carbohydrate
Once protein and fat are set, carbohydrates fill the remaining calories. Carbs are the main fuel for intense training; glycogen stores influence performance in high-volume lifting and endurance work. More active people generally do better with more carbs; sedentary people or those who prefer low-carb eating can reduce them without harming fat loss, provided protein and calories are controlled.
Macros for fat loss
During a calorie deficit, protein becomes even more important because the body is more likely to break down muscle for energy. Higher protein also improves satiety, which makes the deficit easier to sustain.
- Protein: 1.8–2.2 g/kg (or 30–40% of calories).
- Fat: 25–30% of calories, with a minimum of ~0.5 g/kg.
- Carbs: the remainder, prioritised around training.
Macros for muscle gain
In a calorie surplus, protein needs are slightly lower because energy availability spares protein, and extra carbohydrates support training volume. A modest surplus of 200–300 kcal minimises fat gain while supporting growth.
- Protein: 1.6–2.0 g/kg (about 25–30% of calories).
- Fat: 20–30% of calories.
- Carbs: 45–55% of calories to fuel training.
Macros for body recomposition
Body recomposition means losing fat and gaining muscle at the same time, usually while eating close to maintenance. It works best for beginners, people returning after a break, and those with higher body fat. A review by Barakat and colleagues concluded that recomposition is achievable in trained individuals too, provided protein intake is high and training is progressive [3].
- Calories: maintenance to a small deficit (0–250 kcal).
- Protein: 2.0–2.4 g/kg.
- Fat: 25–30% of calories.
- Carbs: the remainder.
Example splits side by side
| Preset | Protein | Carbs | Fat | Best for |
|---|---|---|---|---|
| Balanced | 30% | 40% | 30% | General fat loss and health |
| High protein | 40% | 35% | 25% | Cutting, recomposition |
| Low carb | 35% | 25% | 40% | Appetite control, less active days |
| Keto | 25% | 5% | 70% | People who prefer very low carb |
| Preset | Protein (g) | Carbs (g) | Fat (g) |
|---|---|---|---|
| Balanced | 150 | 200 | 67 |
| High protein | 200 | 175 | 56 |
| Low carb | 175 | 125 | 89 |
| Keto | 125 | 25 | 156 |
Does low-carb beat low-fat for fat loss?
Not when calories and protein are matched. In the DIETFITS randomised trial, 609 adults followed either a healthy low-fat or healthy low-carbohydrate diet for 12 months. Weight loss was nearly identical (about 5.3 kg vs 6.0 kg), with no significant difference between groups [4]. Metabolic ward studies by Hall and colleagues similarly found no meaningful fat-loss advantage for low-carb diets at equal calories [5]. The best macro split is the one that keeps protein high and that you can follow consistently.
Practical tips for hitting your macros
- Build every meal around a protein source (25–40 g per meal across 3–5 meals).
- Use carbs strategically: more on training days and around workouts.
- Choose mostly whole foods; fibre helps fullness and gut health (aim for 25–35 g/day).
- Track for a few weeks to learn portions, then use the plate method if you prefer.
- Get ready-made meals that match your macros with our AI meal planner or see the budget meal prep blueprint.
Summary
Calories decide the direction of the scale; protein decides how much of the change is fat versus muscle. Set protein at 1.6–2.2 g/kg, keep fat above about 20–25% of calories, and fill the rest with carbohydrates based on activity and preference. Start with your TDEE, then split it with the macro calculator.
Put this into practice
Calculate your macros →References
- Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018;52(6):376–384.
- Jäger R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition position stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20.
- Barakat C, Pearson J, Escalante G, Campbell B, De Souza EO. Body recomposition: can trained individuals build muscle and lose fat at the same time? Strength Cond J. 2020;42(5):7–21.
- Gardner CD, Trepanowski JF, Del Gobbo LC, et al. Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults: the DIETFITS randomized clinical trial. JAMA. 2018;319(7):667–679.
- Hall KD, Guo J. Obesity energetics: body weight regulation and the effects of diet composition. Gastroenterology. 2017;152(7):1718–1727.
Educational content only, not medical advice. See our medical disclaimer.