"Macros" is short for macronutrients — the three nutrients that provide all the calories in food: protein, carbohydrates, and fat. While total calorie intake determines whether you gain or lose weight, the distribution of those calories across macros influences how much of the weight change comes from fat versus muscle, how hungry you feel, and how well you perform physically.
This guide explains what each macro does, how many grams you need per day for your goal, and how to calculate your personal macro targets — with worked examples for weight loss and muscle gain.
The Three Macronutrients
These calorie values — 4/4/9 — are the Atwater factors, established through direct calorimetry research and used universally on food nutrition labels. Alcohol provides 7 kcal per gram but is not considered a macronutrient because it provides no essential nutritional function.
Example: 150g protein + 200g carbs + 60g fat
= (150 × 4) + (200 × 4) + (60 × 9)
= 600 + 800 + 540
= 1,940 kcal total
What Each Macro Does
Protein — the priority macro
Protein is the only macro the body uses to build and repair tissue — including muscle, immune cells, enzymes, and hormones. Unlike carbohydrates and fat, the body does not store protein; it must be obtained continuously from food.
During a calorie deficit, insufficient protein accelerates muscle loss (a process called catabolism). Research consistently shows that higher protein intakes during fat loss phases better preserve lean muscle — the metabolically active tissue that keeps your resting calorie burn elevated. A meta-analysis by Morton et al. (2018) in the British Journal of Sports Medicine, covering 49 studies and 1,863 participants, found that approximately 1.62 g/kg/day maximises muscle gain from resistance training, with benefits seen up to approximately 2.2 g/kg/day.
Protein is also the most satiating macronutrient per calorie. A controlled trial by Weigle et al. (2005) found that increasing protein from 15% to 30% of calories reduced ad libitum caloric intake by an average of 441 kcal/day — without any explicit calorie restriction.
Carbohydrates — primary fuel
Carbohydrates are the body's preferred fuel source, particularly for the brain (which uses approximately 120g of glucose per day) and for high-intensity exercise. There is no established minimum daily requirement for carbohydrate — the body can synthesize glucose from amino acids and glycerol — but the Dietary Reference Intakes (Institute of Medicine, 2005) recommend a minimum of 130g/day to supply adequate glucose to the brain without reliance on ketone bodies.
Carbohydrate quality matters as much as quantity. Whole food sources — vegetables, legumes, fruit, whole grains — provide fibre, micronutrients, and slower glucose release compared to refined carbohydrates. The Acceptable Macronutrient Distribution Range (AMDR) for carbohydrates is 45–65% of total calories.
Fat — essential, not optional
Dietary fat is essential for absorbing fat-soluble vitamins (A, D, E, K), producing steroid hormones (including sex hormones), maintaining cell membrane integrity, and supporting neurological function. Fat intake below approximately 20% of total calories is associated with impaired hormonal function in both sexes. The AMDR for fat is 20–35% of total calories.
The type of fat consumed also matters for cardiovascular health. Unsaturated fats (found in olive oil, avocado, nuts, fatty fish) are associated with better lipid profiles than saturated fats, which in excess are associated with raised LDL cholesterol in population studies.
How Much Protein Do You Actually Need?
| Goal | Recommended Protein Intake | Source |
|---|---|---|
| Sedentary adult (minimum) | 0.8 g/kg/day | IOM RDA, 2005 |
| Active adult / general health | 1.2–1.6 g/kg/day | Stokes et al., 2018 |
| Fat loss (preserving muscle) | 1.6–2.2 g/kg/day | Helms et al., 2014 |
| Muscle gain (resistance training) | 1.6–2.2 g/kg/day | Morton et al., 2018 |
| High-volume athletes | Up to 2.4 g/kg/day | Stokes et al., 2018 |
Note that protein requirements are based on lean body mass in athletes with very low body fat. For individuals with overweight, calculating targets from total body weight can overstate needs — using a target body weight or an adjusted weight is common practice in clinical dietetics.
Five Common Macro Splits Compared
There is no single correct macro ratio. The best split is the one you can adhere to consistently while hitting your protein target. Here are the five most commonly used approaches:
| Approach | Carbs | Protein | Fat | Best For |
|---|---|---|---|---|
| Balanced | 40% | 30% | 30% | Most people; easy to sustain |
| High-protein | 35% | 40% | 25% | Fat loss; muscle preservation; hunger control |
| Low-carb | 20% | 35% | 45% | Those who prefer lower carbs; blood sugar management |
| Ketogenic | 5% | 25% | 70% | Specific medical contexts; personal preference |
| High-carb | 55% | 25% | 20% | Endurance athletes; high training volume |
Total calorie intake is the primary determinant of body weight change. A landmark clinical trial by Hall et al. (2016) assigned participants to an isocaloric ketogenic diet (very low carb) or a standard diet for four weeks under controlled conditions. Despite large differences in macro composition, fat loss did not significantly differ between groups when calories were matched.
The practical implication: no macro split has a fat loss advantage that overrides the calorie balance. The reason high-protein diets often outperform lower-protein diets in real-world studies is primarily because protein is more satiating — it naturally reduces total calorie intake — not because protein has a special fat-burning property at equal calorie intakes.
Step-by-Step: How to Calculate Your Macro Targets
Follow these four steps to calculate your daily macro targets:
Step 1 — Find your TDEE. Use your age, sex, height, weight, and activity level to calculate your Total Daily Energy Expenditure. The BodyMetric TDEE Calculator runs all four BMR formulas simultaneously.
Step 2 — Set your calorie target. For fat loss: subtract 250–500 kcal from TDEE. For muscle gain: add 100–250 kcal. For maintenance: use TDEE directly. The Calorie Deficit Calculator checks that your target stays above the safe minimum (1,200 kcal for women / 1,500 kcal for men).
Step 3 — Choose a macro split. Select one of the five splits above based on your preferences and goal. If in doubt, start with Balanced (40/30/30) or High-Protein (35/40/25) for fat loss.
Step 4 — Convert percentages to grams. Multiply your calorie target by each macro's percentage, then divide by the calorie-per-gram value (4 for protein and carbs, 9 for fat).
Carbs (g) = Calorie target × Carbs% ÷ 4
Fat (g) = Calorie target × Fat% ÷ 9
Worked Example: Fat Loss
35-year-old woman, 70 kg, TDEE 2,100 kcal, fat loss goal. Daily calorie target: 1,600 kcal (500 kcal deficit).
Option A — Balanced (40C / 30P / 30F):
Protein at 1.71 g/kg is within the recommended fat-loss range (1.6–2.2 g/kg). This is a good starting point for most people.
Option B — High-Protein (35C / 40P / 25F):
Protein at 2.29 g/kg is at the upper end of the evidence-supported range. This approach is appropriate for those prioritising muscle retention, particularly during more aggressive deficits.
Worked Example: Muscle Gain
28-year-old man, 75 kg, TDEE 2,600 kcal, intermediate lifter. Calorie target: 2,800 kcal (200 kcal surplus).
At 2,800 kcal with a 40% protein split, protein comes out at 3.73 g/kg — above the evidence-supported maximum for muscle gain (~2.2 g/kg). In this case, it is better to set an absolute protein target first (e.g., 165 g/day = 2.2 g/kg × 75 kg), then allocate remaining calories to carbs and fat for energy and performance. The BodyMetric Macro Calculator performs this check automatically and flags when a percentage-based split produces more protein than is physiologically beneficial.
How to Track Your Macros
Tracking macros requires knowing the macro content of the foods you eat. There are two main practical approaches:
- Food tracking apps (MyFitnessPal, Cronometer, MacroFactor) — scan barcodes or search a database to log meals. Most show protein, carbs, and fat alongside calories. Cronometer is generally considered the most accurate for micronutrient data.
- Food labels — nutrition facts panels list grams of total fat, carbohydrate, and protein per serving. Check the serving size carefully; many packages contain two or more servings.
A few practical tracking notes:
- Weigh food on a kitchen scale (grams) rather than using volume measurements — protein content of "1 cup of chicken" can vary considerably depending on how tightly packed it is.
- Track for 2–4 weeks to build awareness of your typical diet, then reassess whether you need to continue logging every meal.
- Aim to hit your protein target first; carbs and fat can flex more freely around it while staying within your calorie budget.
- Restaurant meals are the largest source of tracking error — portion sizes and cooking oils are often much larger than estimated.
Each macronutrient requires a different amount of energy to digest, absorb, and metabolize — known as the thermic effect of food (TEF). Protein has a TEF of approximately 20–30% of its calorie content (meaning 100 kcal of protein costs around 20–30 kcal to process). Carbohydrates have a TEF of 5–10%, and fat has a TEF of 0–3%. This means that two diets identical in total calories but different in protein content will result in slightly different net energy absorption — a high-protein diet effectively delivers fewer usable calories from the same total intake. This effect contributes to the satiety and body composition advantages observed with higher protein diets in controlled research.
More Free Tools on BodyMetric
Use these tools together to build a complete nutrition plan:
- TDEE Calculator — Step 1: find your daily calorie expenditure across all 4 BMR formulas
- Calorie Deficit Calculator — Step 2: set a safe calorie target for fat loss with minimum-threshold check
- Calorie Surplus Calculator — for muscle gain phases: calorie target with muscle-to-fat gain ratio
- Weight Loss Timeline Calculator — week-by-week projection with metabolic adaptation simulation
- BMI Calculator — WHO classification and healthy weight range
- Body Fat % Calculator — track body composition change alongside the scale
- Ideal Weight Calculator — four clinical goal weight formulas
- Water Intake Calculator — daily hydration target adjusted for activity and climate
This article is provided for general educational and informational purposes only. Macronutrient recommendations are population-level estimates derived from research and do not constitute personalised dietary advice. Individual requirements vary based on health status, age, medications, activity type, and other factors not captured in standard formulas. Individuals with medical conditions affecting protein metabolism (such as chronic kidney disease), diabetes, or eating disorder history should consult a registered dietitian or qualified healthcare professional before making significant changes to their dietary macronutrient composition.
References
- Institute of Medicine. (2005). Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. National Academies Press.
- Morton, R. W., Murphy, K. T., McKellar, S. R., Schoenfeld, B. J., Henselmans, M., Helms, E., Aragon, A. A., Devries, M. C., Banfield, L., Krieger, J. W., & Phillips, S. M. (2018). 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. British Journal of Sports Medicine, 52(6), 376–384.
- Weigle, D. S., Breen, P. A., Matthys, C. C., Callahan, H. S., Meeuws, K. E., Burden, V. R., & Purnell, J. Q. (2005). A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations. American Journal of Clinical Nutrition, 82(1), 41–48.
- Helms, E. R., Aragon, A. A., & Fitschen, P. J. (2014). Evidence-based recommendations for natural bodybuilding contest preparation: Nutrition and supplementation. Journal of the International Society of Sports Nutrition, 11, 20.
- Hall, K. D., Chen, K. Y., Guo, J., Lam, Y. Y., Leibel, R. L., Mayer, L. E., Reitman, M. L., Rosenbaum, M., Smith, S. R., Walsh, B. T., & Ravussin, E. (2016). Energy expenditure and body composition changes after an isocaloric ketogenic diet in overweight and obese men. American Journal of Clinical Nutrition, 104(2), 324–333.
- Stokes, T., Hector, A. J., Morton, R. W., McGlory, C., & Phillips, S. M. (2018). Recent perspectives regarding the role of dietary protein for the promotion of muscle hypertrophy with resistance exercise training. Nutrients, 10(2), 180.
- Paddon-Jones, D., Westman, E., Mattes, R. D., Wolfe, R. R., Astrup, A., & Westerterp-Plantenga, M. (2008). Protein, weight management, and satiety. American Journal of Clinical Nutrition, 87(5), 1558S–1561S.
- Halton, T. L., & Hu, F. B. (2004). The effects of high protein diets on thermogenesis, satiety and weight loss: A critical review. Journal of the American College of Nutrition, 23(5), 373–385.