Things You Should Have Learnt in School: Macronutrients Explained – Protein, Carbs, and Fat

What fuels our bodies and keeps us alive at the most basic level? The answer: macronutrients - the nutrients we need in the largest amounts. Whether you’re hitting the gym, aiming to achieve a healthy weight, or just trying to eat a little better, understanding these dietary building blocks is essential. In this comprehensive guide, we’ll explain macronutrients in detail, clear up common myths, and give you practical tools to find your own balance.

Definition of Macronutrients

Let’s get macros explained simply: macronutrients are the main nutrients your body requires in significant quantities to function and survive. They include carbohydrates, protein, and fat. Unlike vitamins and minerals (which are needed only in tiny amounts), these provide the bulk of our dietary energy:

• Carbohydrates: 4 calories per gram

• Protein: 4 calories per gram

• Fat: 9 calories per gram

Each macro plays distinct roles in providing and storing energy and ensuring vital processes run smoothly.

Macronutrients vs. Micronutrients

• Macronutrients (carbs, protein, fat): Provide energy and building blocks for growth and bodily functions. Think “quantity” - we need to eat tens or hundreds of grams of them daily.

• Micronutrients (vitamins, minerals): Needed in much smaller amounts (hence ‘micro’), but essential for things like immune function, bone health and hydration.

Example: Eating a bowl of porridge gives you carbohydrates (a macro) for energy, plus iron and B vitamins (micros) for red blood cell formation and energy metabolism, respectively.

The Three Main Types of Macronutrients

Carbohydrates: The Body’s Primary Fuel

Carbohydrates are your body’s preferred and most accessible source of energy. They’re ultimately broken down into glucose, which fuels all our cells, from our brains to our muscles.

Function: Direct energy supply for organs, especially the brain and nervous system

Complex vs. Simple Carbs:

• Complex: Whole grains, legumes, vegetables—slower to digest, more fibre, steadier energy

• Simple: Table sugar, honey, fruit juice—quicker to digest, faster release of glucose into the blood, and therefore energy

Dietary Sources:

• Whole grains (rice, pasta, quinoa, oats)

• Fruits and starchy vegetables (bananas, potatoes, sweetcorn)

• Legumes and beans (lentils, chickpeas)

• Confectionery and sugary drinks/snacks

• Baked goods

Proteins: Building Blocks for Life

Protein isn’t just for athletes: it’s fundamental for every cell in your body.

Function:

• Forms the structure of muscles, organs, skin, and hair

• Enables repair and growth

• Supports immune function and hormone production

• Transports oxygen around the body

Complete vs. Incomplete Proteins:

• Complete: Contains all nine essential amino acids (e.g., eggs, dairy, fish, soy, quinoa)

• Incomplete: Missing one or more essential amino acids (e.g., most grains, nuts, pulses), but can be combined for adequacy, especially in plant-based diets

Food Sources:

• Animal: Meat, fish, eggs, dairy

• Plant: Beans, peas, lentils, tofu, tempeh, nuts, seeds

Fats: Essential for Health

Contrary to outdated diet advice, fat isn’t your enemy - it’s crucial for long-term health.

Function:

• Forms cell membranes

• Helps absorb fat-soluble vitamins (A, D, E, K)

• Hormone production

• Long-term energy storage  

Saturated vs. unsaturated:

• Saturated: typically found in animal products. This form of fat is associated with elevated cholesterol levels, so it’s important to moderate intake.

• Unsaturated: typically found in plant foods and fish. Swapping saturated for unsaturated fat is associated with improved blood lipids, which in turn is linked with a decreased risk of heart disease. Certain types (omega-3 and omega-6) are essential to our diets.

Sources:

• Saturated: butter, lard, cheese, fatty cuts of meat, coconut

• Unsaturated: oily fish, avocado, olives, nuts, seeds, vegetable oil

Macronutrient Ratios and Daily Requirements

Recommended Macronutrient Percentages

The European Food Safety Authority recommends the following daily macronutrient ranges:

• Carbohydrates: 45–65% of calories

• Protein: 10–35% of calories

• Fat: 20–35% of calories

These ranges support adequate nutrition for most adults, though individual needs vary.

Adjusting Macros for Your Lifestyle

So what do ‘macros’ look like in real life? Macro needs depend on age, activity, health goals, ethics, and more:

• Active individuals may need more protein (e.g. up to 1.2–1.6g/kg body weight) to support muscle repair.

• Older adults benefit from increased protein to preserve lean mass and slow age-related muscle loss (sarcopenia).

• Plant-based diets sometimes require a bit of protein planning to obtain all essential amino acids.

• Weight loss often involves shifting to modestly higher protein for satiety and lean mass while reducing refined carbs or excess fats.

Remember, no single ratio fits all. Listen to your body, adjust with life changes, and seek guidance if needed.

Practical Tips for a Balanced Macro Diet

Navigating food macros explained doesn’t need to be overwhelming. Here’s a practical approach to try:

Visualise your plate:  ½: non-starchy veggies and fruit, ¼: lean protein (beans, tofu, chicken, fish), ¼: complex carbs (quinoa, whole grains, sweet potato), spoonful healthy fats (seeds, nuts, olive oil)

• Grilled salmon, brown rice, broccoli, sesame oil drizzle

• Lentil curry, rice, spinach, pumpkin seeds

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When to Seek Professional Guidance

Consider consulting a registered dietitian or nutritionist if:

• You have underlying health conditions (diabetes, kidney disease, GI disorders)

• You have unexplained weight changes or nutrient deficiencies

• You’re an athlete with demanding performance needs

• You’re transitioning to a novel diet (e.g., vegan, low-carb)

• You’re experiencing stress or an unhealthy fixation on food choices

A professional can help customise your macro balance to safely match your needs and goals.

Key Takeaways

• Macronutrients explained: Carbohydrates, protein, and fat are core to health, each serving distinct roles.

• Quality and ratio both matter: Focus first on a balanced, whole-food-based plate rather than specific numbers.

• Macro needs vary: Adjust ratios for age, activity, ethics, body goals, and life stage.

• Professional support: Seek guidance if you have particular health or performance goals.

Edited by Amy Wood, Huel Senior Nutritionist