Diet and nutrition and their effect on physical activity and performance — AQA A-Level Physical Education

This topic explores how diet and nutrition influence physical activity and sports performance. It covers the macronutrients (carbohydrates, fats, proteins), micronutrients (vitamins, minerals, water), and the role of each in energy production, recovery, hydration, and body composition. Students learn to apply nutritional principles to different sporting contexts, including pre-, during, and post-exercise nutrition, and to evaluate ergogenic aids such as creatine and caffeine.

Understanding diet and nutrition is essential for optimising performance, delaying fatigue, and preventing injury or illness. It links closely with energy systems, recovery strategies, and sports psychology (motivation and adherence). In AQA A-Level PE, this topic is examined through multiple-choice, short-answer, and extended-writing questions, often requiring students to analyse data or apply knowledge to a specific athlete's scenario.

• →Carbohydrates are the primary fuel for high-intensity exercise, stored as glycogen in muscles and liver; fats are the main fuel for low-intensity, long-duration exercise; protein is essential for muscle repair and growth but contributes minimally to energy production.
• →The glycaemic index (GI) ranks carbohydrates by their effect on blood glucose; low-GI foods provide sustained energy, high-GI foods provide rapid energy and aid recovery.
• →Hydration is critical for maintaining blood volume, regulating body temperature, and preventing dehydration, which can impair performance; electrolyte balance (sodium, potassium) is also important.
• →Micronutrients (vitamins and minerals) do not provide energy but are essential for energy metabolism, oxygen transport, bone health, and immune function; deficiencies can impair performance.
• →Nutritional strategies must be tailored to the sport, intensity, duration, and individual athlete, including carbohydrate loading, protein timing, and fluid replacement.

• Carbohydrates are the predominant fuel for high-intensity exercise and are stored as glycogen in muscle and liver.
• Fats are oxidised for energy at lower intensities and over longer durations, sparing glycogen stores.
• Proteins provide amino acids for muscle repair and adaptation, with a minor energy contribution during prolonged exercise.
• Vitamins and minerals act as cofactors in energy metabolism and as electrolytes that support hydration and muscle function.
• Water and dietary fibre support transport, temperature regulation and digestive health relevant to training and performance.
• Carbohydrate is the body's preferred fuel for exercise, stored as glycogen in the liver and muscles.
• It is broken down to glucose for ATP resynthesis, providing approximately 17 kJ (about 4 kcal) per gram.
• Aerobic glycolysis yields a net gain of 2 ATP and 2 pyruvate per glucose molecule, while anaerobic glycolysis yields 2 ATP.
• Glycogen depletion limits performance in endurance events lasting more than about 60–90 minutes.
• Athletes manipulate carbohydrate intake before, during and after exercise to maintain blood glucose and replenish stores.
• Fibre is a type of carbohydrate that cannot be digested by human enzymes.
• It adds bulk to the diet and promotes satiety.
• It helps regulate bowel function by preventing constipation and reducing the risk of diverticular disease.
• Soluble fibre can help lower blood cholesterol and slow glucose absorption.
• Insoluble fibre adds bulk and speeds transit through the gut.
• The UK guideline for adults is about 30 g per day.
• Athletes should increase fibre gradually alongside adequate fluid to avoid gastrointestinal discomfort during exercise.
• Fat provides a concentrated energy source for low-intensity and endurance work and carries fat-soluble vitamins; saturated fat, trans fat and cholesterol are the forms associated with raised cardiovascular risk when eaten in excess.
• Protein supplies amino acids for muscle repair, growth and adaptation after training and contributes a small amount of energy when carbohydrate is limited.
• Vitamin C supports connective tissue repair and helps iron absorption; vitamin D supports bone health; B-12 and B-complex vitamins support red blood cell formation and energy release from food.
• Sodium helps maintain fluid balance and nerve and muscle function; iron is needed for haemoglobin and oxygen transport; calcium supports bone strength and muscle contraction.
• Water maintains hydration and blood volume; dehydration raises heart rate and perceived effort, so fluid should be taken before, during and after physical activity to replace sweat losses.
• Glycogen loading increases muscle glycogen for endurance events but can cause water retention and heavy legs.
• Creatine supplementation increases PC stores for short, explosive bursts of energy, though it may cause unwanted weight gain and cramping.
• Sodium bicarbonate acts as a buffering agent to neutralise lactic acid and delay fatigue, but frequently causes gastrointestinal distress.
• Caffeine stimulates the central nervous system to improve concentration and mobilises fats for energy, yet can cause dehydration and insomnia.
• The effectiveness and risks of any dietary manipulation depend on the specific demands of the sport, the dosage, and individual physiological responses.
• Creatine increases phosphocreatine stores, supporting ATP resynthesis during short, explosive efforts such as sprinting or jumping.
• Sodium bicarbonate buffers hydrogen ions, reducing the acidity that contributes to fatigue in high-intensity exercise lasting about one to several minutes.
• Caffeine is a stimulant that can lower perceived exertion and improve alertness, benefiting endurance performance and some team-sport activities.
• Glycogen loading raises muscle glycogen stores before endurance events by tapering training and increasing carbohydrate intake, delaying fatigue.
• Each aid has side effects and legal or ethical considerations, and effectiveness depends on dose, timing, individual response and the demands of the event.

• 💡Name the food class, its stored or circulating form, and the exercise situation where it matters most.
• 💡Use intensity and duration language, such as high-intensity short duration for carbohydrate and low-intensity long duration for fat.
• 💡Link at least one food class to recovery as well as to performance.
• 💡Avoid listing foods without stating their function, because the command word asks for function.
• 💡Learn the energy yield of carbohydrate in both kJ and kcal, and be ready to identify either unit in a multiple-choice option.
• 💡Distinguish between the roles of liver glycogen (blood glucose maintenance) and muscle glycogen (local fuel for contraction).
• 💡Remember that glycogen depletion is a limiting factor for prolonged endurance exercise (over 60 minutes), not short, high-intensity sprints.
• 💡Learn the difference between soluble and insoluble fibre and give an example of each.
• 💡Remember the UK daily guideline of about 30 g for adults.
• 💡When answering an MCQ, check whether the question asks about health benefits, sources, or effects on exercise.
• 💡Be prepared to explain why athletes might need to moderate fibre intake before competition.
• 💡Link each nutrient to a specific function and a performance consequence rather than listing nutrients alone.
• 💡Use the named examples in the statement, such as vitamin C, vitamin D, B-12, B-complex, sodium, iron and calcium, and state what each does.
• 💡For hydration questions, refer to before, during and after activity and to replacing sweat losses.
• 💡Always link the specific supplement to the correct energy system or type of sport (e.g., creatine for the ATP-PC system).
• 💡Provide both a positive performance effect and a specific negative side effect when evaluating a supplement.
• 💡Use precise terminology, such as 'buffering lactic acid' for sodium bicarbonate or 'mobilising fatty acids' for caffeine.
• 💡Link each aid to the specific energy system or fatigue mechanism it targets, such as phosphocreatine for creatine or buffering for sodium bicarbonate.
• 💡Use precise terms like phosphocreatine, hydrogen ions, perceived exertion and muscle glycogen rather than vague phrases like 'gives energy'.
• 💡When evaluating, consider dose, timing, individual response, side effects and the legal or ethical context of each aid.
• 💡Always link the nutrient to its specific function and the energy system or recovery process it supports. For example, 'carbohydrates are broken down into glucose, which is used in glycolysis to resynthesise ATP'.
• 💡Use specific figures and timing where possible, such as '1.2-1.7 g/kg protein for strength athletes' or '500ml fluid 2 hours before exercise'. This demonstrates precise knowledge.
• 💡When evaluating ergogenic aids, consider both benefits and risks, and cite evidence or studies where appropriate. For example, 'creatine supplementation increases phosphocreatine stores, enhancing ATP-PC system performance, but may cause water retention and gastrointestinal distress'.

• Treating protein as the main fuel for endurance exercise: carbohydrate and fat dominate, with protein making only a small contribution.
• Assuming fat cannot be used during exercise: fat oxidation is important at low to moderate intensities and spares glycogen.
• Describing vitamins as direct energy sources: they act as cofactors that enable energy-releasing reactions.
• Ignoring timing: the function of a food class depends on when it is eaten relative to exercise, not only on what it contains.
• Misunderstanding fatigue mechanisms: stating glycogen depletion causes fatigue in 60–90 seconds, when it actually limits endurance events lasting 60–90 minutes; short-term fatigue is due to acidosis or phosphocreatine depletion.
• Misunderstanding energy yield: assuming carbohydrate provides 4 kcal per gram but failing to recognise this is equivalent to approximately 17 kJ per gram (1 kcal = 4.184 kJ).
• Misunderstanding storage locations: assuming glycogen is stored only in the liver, whereas it is stored in both liver and muscle, with muscle glycogen used locally and liver glycogen maintaining blood glucose.
• Misunderstanding: fibre is a source of energy. Correction: fibre is largely indigestible and contributes little to energy intake, though some soluble fibre can be fermented by gut bacteria.
• Misunderstanding: all fibre is the same. Correction: soluble and insoluble fibre have different roles; soluble fibre can lower cholesterol and slow glucose absorption, while insoluble fibre adds bulk and speeds transit.
• Misunderstanding: a high-fibre diet is always best for athletes. Correction: too much fibre too close to exercise can cause gastrointestinal discomfort; athletes should adjust timing and amount.
• Misunderstanding: fibre is only important for older adults. Correction: fibre is important for all age groups for digestive health and satiety.
• Treating all fat as harmful: saturated fat, trans fat and cholesterol are the risk-linked forms, while unsaturated fat is an essential energy and vitamin-carrying nutrient.
• Assuming protein is the main energy fuel for endurance performance: carbohydrate is the primary fuel, and protein mainly repairs and builds tissue.
• Believing hydration matters only after exercise: fluid taken before and during activity also limits dehydration and the rise in heart rate and perceived effort.
• Confusing the energy systems targeted: for example, thinking creatine benefits marathon runners rather than explosive athletes.
• Ignoring the side effects: assuming supplements like sodium bicarbonate only have positive buffering effects without mentioning gastrointestinal upset.
• Believing glycogen loading is suitable for all sports: it is specifically beneficial for endurance events lasting over 90 minutes, not short sprints.
• Misunderstanding: creatine directly provides energy for endurance events. Correction: creatine increases phosphocreatine stores, which support short, explosive efforts, not prolonged aerobic performance.
• Misunderstanding: sodium bicarbonate works by increasing oxygen delivery. Correction: it acts as a buffer, neutralising hydrogen ions that lower muscle pH during high-intensity work.
• Misunderstanding: caffeine is banned in all sport. Correction: caffeine is permitted by WADA at all times, though it remains a stimulant with side effects and individual variability.
• Misunderstanding: glycogen loading means eating more protein. Correction: glycogen loading involves tapering training while increasing carbohydrate intake to raise muscle glycogen stores.
• Misconception: 'Protein is the main energy source for exercise.' Correction: Carbohydrates are the primary fuel for high-intensity exercise; fats fuel low-intensity exercise; protein is mainly for repair and growth.
• Misconception: 'All fats are bad and should be avoided.' Correction: Unsaturated fats are essential for health, hormone production, and provide energy for low-intensity exercise; only excessive saturated/trans fats are harmful.
• Misconception: 'You should drink as much water as possible during exercise.' Correction: Overhydration can cause hyponatraemia (low blood sodium), which is dangerous; fluid intake should match sweat loss, typically 150-250ml every 15-20 minutes.

1. 1Day 1-2: Learn the definitions and functions of macronutrients (carbohydrates, fats, proteins) and micronutrients (vitamins, minerals, water). Create a table summarising each nutrient's role, food sources, and recommended intake for athletes.
2. 2Day 3-4: Study the glycaemic index and its application to pre-, during, and post-exercise nutrition. Practice applying GI to different sporting scenarios (e.g., a footballer's pre-match meal vs. a marathon runner's during-race nutrition).
3. 3Day 5-6: Investigate hydration strategies, including fluid and electrolyte balance, and the effects of dehydration on performance. Calculate sweat rates and fluid replacement needs for a given athlete.
4. 4Day 7-8: Explore ergogenic aids (creatine, caffeine, bicarbonate, beta-alanine) and their mechanisms, benefits, and risks. Evaluate the evidence for each and consider ethical issues.
5. 5Day 9-10: Complete practice exam questions, including data analysis and 6-mark extended responses. Use mark schemes to identify gaps and refine exam technique.

• 📋Multiple-choice questions testing knowledge of nutrient functions, energy systems, or hydration guidelines. Advice: read all options carefully and eliminate obviously incorrect answers.
• 📋Short-answer questions (2-4 marks) requiring definitions, explanations, or calculations (e.g., carbohydrate requirement, sweat rate). Advice: show your working for calculations and use correct units.
• 📋Data analysis questions where you interpret a graph or table (e.g., blood glucose levels after consuming high vs. low GI foods) and explain the implications for performance. Advice: quote data from the graph and link it to physiological processes.
• 📋Extended-writing questions (6-9 marks) asking you to evaluate nutritional strategies or ergogenic aids for a specific athlete. Advice: structure your answer with an introduction, balanced arguments, and a conclusion, using specialist terminology.