Learn everything about proteins, carbohydrates, and fats - the three macronutrients that fuel your body. Evidence-based guide to understanding and balancing your macros.
Core Health
Core Health Team
What are macronutrients?
Macronutrients are the nutrients your body needs in large amounts to function properly. Unlike micronutrients (vitamins and minerals), which are needed in smaller quantities, macronutrients provide the bulk of your energy and building blocks for growth and repair.
The three macronutrients are:
- Protein - 4 calories per gram
- Carbohydrates - 4 calories per gram
- Fats - 9 calories per gram
Understanding these nutrients and how to balance them is fundamental to achieving any health or fitness goal, whether you're trying to lose fat, build muscle, or simply maintain good health.
Protein: The building block
What protein does
Protein is essential for building and repairing tissues, making enzymes and hormones, and supporting immune function. It's made up of smaller units called amino acids, nine of which are "essential" - meaning your body cannot produce them, so you must obtain them from food.
How much protein do you need?
Research suggests these evidence-based recommendations:
| Goal | Protein Intake |
|---|---|
| General health | 0.8-1.0g per kg bodyweight |
| Muscle building | 1.6-2.2g per kg bodyweight |
| Fat loss | 1.6-2.4g per kg bodyweight |
| Older adults (65+) | 1.0-1.2g per kg bodyweight |
A landmark 2018 meta-analysis published in the British Journal of Sports Medicine found that protein supplementation beyond 1.6g/kg showed diminishing returns for muscle growth, though individual responses vary.
Best protein sources
Complete proteins (containing all essential amino acids):
- Chicken and turkey breast
- Fish (salmon, tuna, cod)
- Eggs
- Dairy (Greek yogurt, cottage cheese)
- Soy products (tofu, tempeh)
Plant proteins (combine for complete amino acid profile):
- Legumes (lentils, chickpeas, black beans)
- Nuts and seeds
- Quinoa (complete protein)
- Whole grains
Use our protein calculator to determine your personal daily target.
Carbohydrates: Your primary fuel source
What carbohydrates do
Carbohydrates are your body's preferred energy source, particularly for high-intensity exercise. When consumed, they're broken down into glucose, which powers your muscles, brain, and nervous system.
Types of carbohydrates
Simple carbohydrates: Quick-digesting sugars found in fruits, honey, and processed foods. They cause rapid blood sugar spikes.
Complex carbohydrates: Longer chains of sugar molecules found in whole grains, vegetables, and legumes. They digest more slowly, providing sustained energy.
Fiber: A type of carbohydrate your body cannot digest. Despite not providing energy, fiber is crucial for:
- Digestive health
- Blood sugar regulation
- Cholesterol management
- Satiety (feeling full)
How many carbohydrates do you need?
Carbohydrate needs vary widely based on activity level:
| Activity Level | Daily Carbs |
|---|---|
| Sedentary | 2-3g per kg bodyweight |
| Moderate exercise (1 hour/day) | 5-7g per kg bodyweight |
| Endurance training (1-3 hours/day) | 6-10g per kg bodyweight |
| Extreme training (4+ hours/day) | 8-12g per kg bodyweight |
For most people focused on general fitness, 3-5g per kg bodyweight is a sensible starting point.
Best carbohydrate sources
Prioritise these complex carbs:
- Oats and whole grain bread
- Brown rice and quinoa
- Sweet potatoes and regular potatoes
- Fruits (bananas, berries, apples)
- Vegetables (especially leafy greens)
- Legumes (beans, lentils)
Limit these simple carbs:
- Sugar-sweetened beverages
- Candy and sweets
- White bread and pastries
- Most breakfast cereals
The glycemic index
The glycemic index (GI) measures how quickly foods raise blood sugar. Low-GI foods (under 55) digest slowly, while high-GI foods (over 70) cause rapid spikes.
For sustained energy and blood sugar control, favour low-to-moderate GI foods, particularly if you're sedentary or managing weight.
Fats: Essential but often misunderstood
What fats do
Dietary fat is essential for:
- Hormone production (including testosterone)
- Absorption of fat-soluble vitamins (A, D, E, K)
- Brain function and mental health
- Cell membrane integrity
- Insulation and organ protection
Despite having more than double the calories per gram compared to protein and carbs, fat is not the enemy. The type of fat matters more than the amount.
Types of dietary fat
Unsaturated fats (generally healthy):
- Monounsaturated: Olive oil, avocados, nuts
- Polyunsaturated: Fatty fish, flaxseed, walnuts
- Omega-3s: Fish oil, chia seeds, salmon (particularly beneficial for inflammation and heart health)
Saturated fats (moderate consumption):
- Found in meat, dairy, coconut oil
- Research is mixed, but limiting to 10% of calories is commonly recommended
- Not as harmful as once thought, but unsaturated fats are still preferable
Trans fats (avoid completely):
- Artificially created through hydrogenation
- Found in some processed foods and margarine
- Strongly linked to heart disease
- Banned in many countries
How much fat do you need?
Most nutrition experts recommend fat comprise 20-35% of total calories. For someone eating 2,000 calories:
- Minimum: 44g (20%)
- Maximum: 78g (35%)
- Sweet spot for most: 55-65g (25-30%)
Athletes and those in caloric deficits may temporarily go lower, but staying below 0.5g per kg bodyweight long-term can affect hormones.
Best fat sources
Emphasise these:
- Extra virgin olive oil
- Avocados
- Fatty fish (salmon, mackerel, sardines)
- Nuts (almonds, walnuts, macadamias)
- Seeds (chia, flax, hemp)
- Eggs (whole, with yolks)
Moderate these:
- Butter and cheese
- Red meat
- Coconut oil
Use our macro calculator to find your optimal fat intake.
Balancing your macronutrients
Step 1: Calculate your calories
Before setting macros, determine your total calorie needs. Your total daily energy expenditure (TDEE) depends on:
- Basal metabolic rate (BMR)
- Physical activity level
- Thermic effect of food
Use our calorie calculator to estimate your needs.
Step 2: Set protein first
Protein should be your anchor. Set it based on your goal (see recommendations above), then distribute remaining calories between carbs and fats.
Step 3: Adjust carbs and fats based on preference
Within reasonable limits, the carb-to-fat ratio is largely personal preference. Some people perform better with higher carbs; others prefer higher fat. Consider:
- Training style (high-intensity exercise benefits from more carbs)
- Personal satiety (fat keeps some people fuller longer)
- Food preferences (more sustainable if you enjoy your diet)
- Medical conditions (diabetics may benefit from lower carbs)
Example macro distributions
For muscle building (70kg person, 2,500 calories):
- Protein: 140g (22% of calories)
- Carbs: 313g (50% of calories)
- Fat: 78g (28% of calories)
For fat loss (70kg person, 1,800 calories):
- Protein: 140g (31% of calories)
- Carbs: 180g (40% of calories)
- Fat: 58g (29% of calories)
For maintenance (70kg person, 2,200 calories):
- Protein: 120g (22% of calories)
- Carbs: 248g (45% of calories)
- Fat: 81g (33% of calories)
Practical tips for tracking macros
Should you track?
Tracking macros isn't for everyone. It can be helpful for:
- Learning portion sizes and food composition
- Optimising performance or body composition
- Ensuring adequate protein intake
It may not be suitable for those with a history of disordered eating or those who find tracking stressful.
How to track effectively
- Use an app: MyFitnessPal, Cronometer, or MacroFactor
- Weigh your food: Estimates are notoriously inaccurate
- Track consistently: At least for 2-4 weeks to learn patterns
- Focus on averages: Daily fluctuations matter less than weekly trends
- Allow flexibility: An 80/20 approach (80% whole foods, 20% treats) is sustainable
Hitting your targets
- Struggling to hit protein? Add protein at breakfast, include Greek yogurt, or consider a supplement
- Carbs too high? Reduce bread, rice, and pasta portions; add more vegetables
- Fat too high? Choose leaner meats, use less oil, watch nuts and cheese portions
- Fat too low? Add avocado, nuts, or olive oil to meals
Common macro myths debunked
"Carbs make you fat"
Excess calories make you fat, regardless of source. Carbs are easily overeaten (especially processed ones), which may be where this myth originated. In a calorie deficit, carbs won't prevent fat loss.
"Eating fat makes you fat"
See above. Fat is calorie-dense, making overeating easier, but in appropriate amounts, dietary fat doesn't cause body fat gain.
"You need to eat every 3 hours"
Meal frequency doesn't significantly impact metabolism or body composition. What matters is total daily intake. Eat in a pattern that fits your lifestyle.
"High protein damages your kidneys"
In healthy individuals, there's no evidence that high protein intake harms kidney function. Those with existing kidney disease should consult a doctor.
Summary
- Macronutrients (protein, carbs, fats) provide calories and essential functions
- Protein should be set first based on your goal (typically 1.6-2.2g/kg for active individuals)
- Carbs fuel activity; needs vary based on training volume
- Fats are essential for hormones and health; prioritise unsaturated sources
- Total calories matter most; macro distribution is secondary
- Tracking can be educational but isn't required for success
References
- Morton RW, 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.
- Burke LM, et al. Carbohydrates for training and competition. J Sports Sci. 2011.
- Sacks FM, et al. Dietary Fats and Cardiovascular Disease: A Presidential Advisory From the American Heart Association. Circulation. 2017.
- Helms ER, et al. A systematic review of dietary protein during caloric restriction in resistance trained lean athletes. Int J Sport Nutr Exerc Metab. 2014.
- Thomas DT, et al. Position of the Academy of Nutrition and Dietetics: Nutrition and Athletic Performance. J Acad Nutr Diet. 2016.
Health disclaimer: This content is for informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare professional before making significant changes to your diet or exercise routine.
