Macronutrients are the substances we need in large amounts to sustain life, support movement, and drive performance. According to the SEHS specification, students must understand the roles of carbohydrates, proteins, and fats, how each is digested and metabolised, and how macronutrient balance can influence performance in different types of physical activity. This learning forms the bedrock of sports nutrition and provides a functional lens through which to view fuelling, recovery, and adaptation.

There are three primary macronutrients: carbohydrates, proteins, and fats. Each plays a distinct and essential role in the body. Although all can contribute to energy production, they do so via different metabolic pathways and serve additional purposes beyond fuelling movement.

Carbohydrates are the body’s preferred energy source, particularly during high-intensity or anaerobic exercise. They are broken down into glucose, which is either used immediately or stored as glycogen in the liver and skeletal muscles. When exercise begins, glycogen is quickly mobilised to meet energy demands. Endurance performance is highly dependent on glycogen stores, and once these are depleted, fatigue sets in. Carbohydrate intake before, during, and after exercise is therefore essential for sustaining energy, preventing performance decline, and promoting recovery.

Proteins are primarily used for the growth, repair, and maintenance of tissues, including muscle, bone, and connective tissue. During periods of intense training, injury recovery, or energy deficit, protein requirements increase. Proteins are composed of amino acids, nine of which are considered essential and must be obtained through the diet. While not a major energy source under normal conditions, proteins can be oxidised for fuel if carbohydrate and fat availability is low. In sports, adequate protein intake supports muscle repair, adaptation, and the development of lean tissue.

Fats are a dense source of energy and are especially important during low- to moderate-intensity exercise. They provide essential fatty acids that the body cannot produce on its own and play key roles in hormone production, cell membrane integrity, and the absorption of fat-soluble vitamins. Fats are stored as triglycerides in adipose tissue and muscle, and although slower to mobilise than carbohydrates, they can provide a sustained energy supply during prolonged activity. Endurance athletes often train to improve fat oxidation efficiency, sparing glycogen and delaying fatigue.

Understanding the appropriate macronutrient balance is essential. Different sports and training goals demand different nutritional strategies. A sprinter requires rapid access to carbohydrate energy, while an ultra-endurance athlete must manage glycogen stores and optimise fat metabolism. A strength athlete requires consistent protein intake to support muscle synthesis, while a team sport player must balance energy demands with their recovery needs.

Micronutrients support the metabolic processes initiated by macronutrients, but without an adequate foundation of carbohydrates, proteins, and fats, the body cannot meet the physiological demands of sports or training. Quality and timing also matter. Nutrient-dense whole foods offer longer-lasting benefits than processed options, and the timing of nutrients around training can significantly influence recovery and adaptation.

In summary, macronutrients are not just fuel but the raw materials for growth, repair, and peak performance. Knowing how to use them effectively is one of the most powerful tools available to any athlete or coach aiming to train smart, recover more efficiently, and perform at their best.