Fuelling for health and performance

· Macronutrients = carbohydrates, proteins and lipids; they provide energy to maintain growth, rest and physical activity.
· Exam focus: link nutrient availability and metabolization to health and performance.
· The relative contribution of each macronutrient depends on body composition, age, sex differences and activity level.
· A strong answer should connect fuelling to the specific demands of the activity rather than giving one generic diet rule.

Macronutrients and performance

· Carbohydrates are the key fuel for many moderate- to high-intensity activities because they can support rapid ATP production.
· Proteins support growth, tissue repair, muscle function and adaptation to training; they are not usually the main exercise fuel.
· Lipids are important for resting metabolism and longer-duration, lower-intensity activity, but are metabolized more slowly than carbohydrates.
· Macronutrient availability affects whether the body can meet the energy demands of exercise and maintain normal physiological function.
· In exams, avoid saying one macronutrient is “best”; instead, explain how fuel use changes with intensity, duration, training status and individual factors.

This diagram helps students distinguish different forms of carbohydrate, a major energy-yielding macronutrient. It is useful when explaining why carbohydrate type and timing can influence fuel availability and gastrointestinal comfort during sport. Source

Individual factors affecting fuelling needs

· Fuelling needs vary with body composition: muscle mass, fat mass and total body size affect energy requirements.
· Fuelling needs vary with age because growth, maturation and recovery demands change across the lifespan.
· Fuelling needs vary with sex differences, including differences that may affect energy availability, fuel use and gastrointestinal responses.
· Fuelling needs vary with activity level: higher training volume or intensity generally increases energy and macronutrient requirements.
· Exam phrase to use: “Nutritional strategies should be individualized to the athlete, activity and performance goal.”

Nutritional strategies before and during exercise

· Pre-exercise nutrition aims to provide enough usable fuel while minimizing gastrointestinal discomfort.
· During-exercise nutrition may be needed when exercise is prolonged or energy demand is high.
· Strategies should be adjusted for the specific demands of the activity, such as duration, intensity, opportunities to eat/drink and risk of stomach upset.
· Strategies should also consider sex differences, age and activity level.
· Key exam link: a nutrition plan can improve performance only if the athlete can tolerate, absorb and use the fuel during the event.
· Practical examples: changing timing, portion size, macronutrient balance or food form before/during exercise to reduce discomfort and support performance.

Low energy availability and RED-S

· Low energy availability (LEA) = the body has insufficient energy to support normal physiological functions needed for optimal health.
· Relative energy deficiency in sport (RED-S) = a consequence of prolonged LEA.
· LEA can occur when energy intake is too low, exercise energy expenditure is too high, or both.
· RED-S is exam-relevant because it links nutrition to health, performance, training adaptation and long-term physiological function.
· Avoid reducing RED-S to only “not eating enough”; the key issue is energy available after exercise demands are accounted for.
· Strong exam wording: “Prolonged LEA compromises normal physiological function, which can impair both health and performance.”

This diagram illustrates how sodium and potassium gradients are maintained across cell membranes. It is useful for explaining why electrolytes are essential for nerve impulses, muscle function and water balance. Source

This diagram provides a visual overview of the human gut microbiome. It supports the HL point that gut microbes can influence nutrient availability, uptake, health and performance. Source

Key exam links and applications

· Link A.2.2 to A.2.3 Energy systems: macronutrient availability affects fuel supply for ATP production.
· Link A.2.2 to A.3.1 Training programmes: nutrition should be periodized to match training load, recovery needs and competition demands.
· Link A.2.2 to A.1.2 Blood glucose regulation: carbohydrate availability interacts with insulin and glucagon to help maintain blood glucose.
· Link A.2.2 to B.1.3 Muscular function: malnutrition or inadequate nutrients can impair contraction, repair and adaptation.
· Link A.2.2 to C.4.2 Stress and coping: anxiety may affect the gut, appetite and gastrointestinal comfort during performance.

Common exam mistakes to avoid

· Do not write that micronutrients provide energy; they support energy transfer but are not energy-yielding fuels.
· Do not describe a “perfect diet” for every athlete; fuelling must be adjusted for individual factors and activity demands.
· Do not ignore gastrointestinal comfort when discussing nutrition before or during exercise.
· Do not confuse LEA with ordinary short-term hunger; LEA means insufficient energy to support physiological function.
· Do not include detailed biochemical pathways unless needed; the syllabus emphasizes application to health and performance.