Macronutrients: Proteins, Fats, and Carbohydrates Explained

Published: February 2026

What Are Macronutrients?

Macronutrients are nutrients required in large quantities by the body. The three macronutrients are protein, carbohydrates, and fat. Each plays distinct roles in supporting bodily functions, and all three are necessary for optimal health.

Proteins

Role in the Body

Proteins are essential for building and repairing tissues, including muscle, skin, hair, and organs. Beyond structure, proteins serve as enzymes that facilitate chemical reactions, as hormones that regulate body functions, and as antibodies that support immune function.

Amino Acids

Proteins are made up of amino acids. The body can synthesise some amino acids, but nine are considered "essential" because the body cannot produce them and must obtain them from food.

Food Sources

Good sources of protein include:

• Animal sources: fish, poultry, meat, eggs, dairy products
• Plant sources: legumes (beans, lentils), nuts, seeds, whole grains, tofu

Protein Requirements

The amount of protein needed varies based on age, sex, activity level, and health status. General guidance suggests approximately 0.8 grams of protein per kilogram of body weight for sedentary adults, with higher requirements for active individuals or those engaging in strength training.

Carbohydrates

Role in the Body

Carbohydrates are the body's preferred energy source, particularly for the brain and nervous system. They're also essential for providing energy during physical activity and for maintaining proper digestive function.

Simple vs. Complex Carbohydrates

Simple carbohydrates include sugars found naturally in fruits and dairy, as well as added sugars in processed foods. They're rapidly absorbed and provide quick energy.

Complex carbohydrates include whole grains, legumes, and vegetables. They contain fibre, are digested more slowly, and provide sustained energy.

Dietary Fibre

Fibre, a type of carbohydrate, is not digested by the body but plays important roles in digestive health, blood sugar regulation, and satiety. Most people benefit from consuming adequate fibre through whole grains, vegetables, fruits, and legumes.

Food Sources

Sources of carbohydrates include:

• Whole grains: brown rice, oats, whole wheat bread, quinoa
• Vegetables: broccoli, sweet potatoes, carrots, leafy greens
• Fruits: apples, berries, oranges, bananas
• Legumes: beans, lentils, chickpeas

Fats

Role in the Body

Dietary fat is essential for hormone production, brain health, vitamin absorption, and cell function. Fat is more energy-dense than protein or carbohydrates, providing 9 calories per gram compared to 4 calories per gram for the other two.

Types of Fats

Unsaturated fats (found in olive oil, nuts, seeds, and fatty fish) are associated with cardiovascular health. Saturated fats (found in meat, dairy, and coconut oil) are solid at room temperature and should be consumed in moderation according to most health guidelines. Trans fats (artificial fats created through hydrogenation) are associated with negative health effects and are best avoided.

Omega-3 and Omega-6 Fatty Acids

These polyunsaturated fats are considered "essential" because the body cannot produce them. Omega-3 sources include fatty fish (salmon, mackerel), flaxseeds, and walnuts. Omega-6 sources include vegetable oils and nuts. A balanced ratio of these fats supports health.

Food Sources

Sources of healthy fats include:

• Olive oil and other plant oils
• Nuts and seeds
• Fatty fish (salmon, sardines, mackerel)
• Avocados
• Eggs

Macronutrient Balance

A balanced diet typically includes all three macronutrients in varying proportions. British nutrition guidelines recommend:

• About 50% of calories from carbohydrates
• About 15-20% of calories from protein
• About 30-35% of calories from fat

Individual needs may vary based on health status, activity level, and personal circumstances. Some people may benefit from different macronutrient ratios, which is why consulting a healthcare professional can be helpful.

Micronutrients and Overall Nutrition

While macronutrients provide energy and structure, micronutrients—vitamins and minerals—are essential for supporting countless bodily functions. Eating a varied diet rich in different foods ensures adequate intake of both macro and micronutrients.

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