Energy use, diet, nutrition and hydration — AQA GCSE Physical Education

This statement covers two linked ideas about energy. First, energy is measured in calories, written as Kcal (kilocalories), so a food label or a diet plan expresses energy in these units. Second, the body obtains that energy from the food we eat: the macronutrients in food are broken down and release energy that fuels muscle contraction and other body functions. Carbohydrates are the main energy source for exercise, fats provide a concentrated store of energy, and protein is used mainly for growth and repair but can contribute energy. A performer's energy needs rise with the intensity and duration of activity, so a marathon runner needs more energy from food than a sedentary person. When answering, check the unit named and the source of the energy.

Energy intake is measured in kilocalories (Kcal) per day. The specification gives reference figures of about 2,500 Kcal/day for the average adult male and about 2,000 Kcal/day for the average adult female. These are averages, not fixed targets for every person: the statement stresses that the requirement is dependent upon further factors. In an MCQ you must recognise both reference values and, crucially, the idea that individual need varies. A physically active adult male training several times a week can expend well above 2,500 Kcal/day, while a sedentary adult of the same sex needs less. Treat the figures as population averages and select the option that reflects dependence on individual factors such as activity level, age, body size and sex.

Age is one factor on which daily energy requirement depends. The specification's reference averages of about 2,500 Kcal/day for the average adult male and about 2,000 Kcal/day for the average adult female apply to adults, so a learner must recognise that younger and older people differ. Growth during childhood and adolescence raises energy needs relative to body size, while energy expenditure and, often, lean body mass tend to fall in later life, lowering requirement. In an MCQ, age may appear as a correct factor explaining variation from the averages, or as a distractor alongside unrelated items. Link age to changes in growth, activity patterns and body composition rather than treating it as a single fixed number.

Gender is one of the individual factors that affect energy use and therefore diet and hydration needs. In this section you learn that males and females typically differ in body composition and average body mass, so their basal metabolic rate and the energy cost of the same activity can differ. A learner should be able to pick the correct explanation from options: for example, that a person with greater muscle mass and body mass generally uses more energy at rest and during exercise, and that this often, though not always, means males use more energy than females of the same age and size. Recognise that gender is a general factor, not a rule for every individual, and link it to energy balance, diet and hydration.

Height is an individual factor that affects energy use and so influences diet and hydration. In this section you learn that taller people usually have a larger body mass and greater surface area, which raises basal metabolic rate and the energy needed to move the body during activity. A learner should be able to select the correct explanation from options: for example, that a taller, heavier performer generally expends more energy than a shorter, lighter performer doing the same activity, and that this changes energy balance and dietary and fluid requirements. Recognise that height is a general factor and that body mass, muscle mass and activity level also matter for each individual.

Energy expenditure means the energy a performer uses up, measured in kilojoules or kilocalories, and exercise is the biggest controllable part of it. Working muscles need ATP, rebuilt through aerobic respiration when oxygen supply keeps pace and through anaerobic respiration when it does not. Longer, harder or more frequent sessions raise total expenditure: a 30-minute steady run costs more than a 10-minute walk, and a heavier performer typically spends more than a lighter one doing the same task. Learners should link expenditure to energy balance: intake above expenditure stores surplus as fat, while expenditure above intake draws on stores. Compare two activities by duration, intensity and body mass rather than guessing a single figure.

A balanced diet supplies carbohydrate, fat, protein, vitamins, minerals, fibre and water in the right proportions for health and performance. The key reason for variety is that no single food contains all these nutrients in suitable amounts: bread is rich in carbohydrate but low in vitamin C, while oranges supply vitamin C but little protein. Eating across food groups therefore fills nutrient gaps. Learners should connect each nutrient to a function, such as carbohydrate for energy, protein for growth and repair, and water for hydration, then explain why relying on one food would leave needs unmet. Recognise that a balanced diet also matches energy intake to expenditure, so quantity matters as well as variety.

A balanced diet means eating a wide variety of foods in the right proportions so the body receives everything it needs. Variety matters because no single food supplies every nutrient: carbohydrates and fats provide energy, protein supports growth and repair, and vitamins and minerals (such as vitamin C and calcium) support functions like immunity and strong bones. Fibre aids digestion and water maintains hydration. The key idea is suitability and balance rather than eating only 'healthy' foods or cutting out whole food groups. In a multiple-choice question, read each option and test it against two questions: does it include a range of foods, and does it supply the nutrients, vitamins and minerals the body requires? An option that removes a food group entirely, or that relies on one food only, fails the balance test.

The reasons for a balanced diet link food choices to how the body works and performs. A balanced diet supplies energy for activity and everyday function, provides nutrients for growth and repair of tissues, and supports the immune system and general health. It helps maintain a suitable body composition and provides the vitamins and minerals needed for functions such as strong bones and healthy skin. For a performer, good nutrition supports training, recovery and consistent performance, while poor balance can lead to tiredness, poor recovery or deficiency problems. In a multiple-choice question, match each option to a clear reason: energy provision, growth and repair, health and immunity, or performance and recovery. Reject options that describe a single food or an unbalanced approach, because the question asks for reasons for balance.

Energy taken in through food that the body does not use for movement, growth or maintenance is converted and stored as fat. If a performer regularly eats more energy than they expend, the store grows and body mass rises, which can lead to obesity. Saturated fat is the type to watch: it is energy-dense and, eaten in excess, is linked with weight gain and with raised cholesterol and heart risk. A useful method is to compare energy in with energy out: a footballer who trains hard uses more energy than a sedentary student of the same size, so the same portion affects them differently. Reducing saturated fat and matching intake to activity helps keep the store in check.

For activity to be performed well, the body needs energy that is suitable: enough of it, from the right sources, and released at the right rate for the demands of the event. Carbohydrate is the main fuel for higher-intensity work, so a performer who eats appropriate carbohydrate before exercise has suitable energy available; fat supplies energy for longer, lower-intensity work. Timing matters too, because food needs time to be digested, and hydration supports the reactions that release energy. A runner who eats a balanced meal a few hours before a race gives the body time to make suitable energy available, whereas eating a large fatty meal immediately beforehand leaves them sluggish.

Nutrients are the substances in food and drink that the body uses for three distinct jobs. Energy: carbohydrate and fat are oxidised to release the energy that fuels muscle contraction, so a performer who eats too little of them runs short of fuel. Growth: protein supplies amino acids that build and repair tissue, which matters for a growing teenager and for repairing muscle after training; vitamins and minerals support these processes and keep systems such as bone and blood healthy. Hydration: water replaces fluid lost in sweat and in exhaled air, helping to control body temperature and keep blood volume up during exercise. A correct answer links each nutrient to the job it does rather than treating all nutrients as interchangeable fuel.

Nutrition covers what each nutrient does and how much of the diet it should make up. Carbohydrate is the main fuel for exercise and should form 55–60% of a balanced diet. Fat is a concentrated energy store and also carries fat-soluble vitamins, at 25–30%. Protein builds and repairs tissue and supports growth, at 15–20%. Vitamins and minerals are needed in small amounts to keep systems such as bone, blood and nerves working and to support energy release, but they are not given a percentage band in this specification. A balanced diet therefore combines these nutrients in the stated proportions, and a correct answer matches a nutrient to its role and to its percentage band without swapping them.

Carbohydrates are stored as glycogen in the muscles and liver and are broken down to glucose, which fuels ATP resynthesis. Because carbohydrate can be broken down quickly, with or without oxygen, the body relies on it as its main and preferred fuel across exercise types and intensities. At high intensity the demand for energy is fast, so carbohydrate is the dominant fuel; at lower intensity the body can use it more slowly and economically. This is why a sprinter and a games player both depend heavily on carbohydrate, and why a performer who has not eaten enough carbohydrate tires sooner. The statement stresses both 'main' and 'preferred', so a correct answer must recognise carbohydrate as the body's first-choice fuel at every intensity, not only during short explosive efforts.

Fat is a second energy source stored in the body and broken down to release energy. Gram for gram it provides more energy than carbohydrate, but it is broken down more slowly and needs plenty of oxygen. This means fat makes its greatest contribution at low intensity, such as walking or steady jogging, where the body has time and oxygen to use it. As intensity rises, the body switches towards carbohydrate because it can be broken down faster. A correct answer therefore recognises two points: fat yields more energy than carbohydrate, and fat is used mainly at low intensity. It should not claim fat is the preferred fuel overall, because carbohydrate remains the main and preferred source.

Protein is the nutrient a performer uses to build and rebuild muscle tissue. During training, muscle fibres suffer small amounts of damage and are remodelled; amino acids from dietary protein supply the material for that growth and repair, which is why protein needs are raised in periods of heavy training or recovery from injury. Good sources include lean meat, fish, eggs, dairy foods, beans, lentils, nuts and soya. Protein can also be broken down for energy when carbohydrate supplies run low, but its defining role in this specification is growth and repair of muscle tissue rather than being the body's main fuel. A useful exam habit is to link the nutrient to the performer's situation: a games player recovering from a hard session needs protein to repair muscle, whereas a marathon runner topping up before a race is mainly concerned with carbohydrate.

Vitamins and minerals are micronutrients needed in small amounts, and their role is to keep the body systems working efficiently and to support general health. They do not supply energy in the way carbohydrate, fat and protein do; instead they assist processes such as energy release, bone and muscle function, oxygen transport and immune defence. Vitamins are found in fruit, vegetables, dairy foods and oily fish, while minerals come from sources such as dairy foods for calcium, red meat and leafy vegetables for iron, and bananas for potassium. A performer who eats a varied, balanced diet usually obtains enough of both, but a restricted diet can leave systems working less efficiently, affecting recovery, bone strength or oxygen transport.

Water balance means matching the water your body loses with the water you take in, so body cells keep working properly. You lose water mainly through sweat, urine and breathing, and you gain it from drinks and food. During exercise you sweat more to lose heat, so you must drink to replace the loss. If you lose more water than you replace, you become dehydrated. Dehydration is the condition where the body has lost more water than it has taken in, so it cannot work efficiently. Signs include thirst, dark urine, tiredness, headache and poor concentration. Dehydration reduces performance because blood volume falls, heart rate rises and the body cannot cool itself well.

Keeping water balance means replacing the water your body loses so that intake matches loss. When you exercise, you sweat more to control body temperature, so you lose extra water. Drinking before, during and after exercise replaces that loss and keeps water balance. Maintaining this balance prevents dehydration, which is the condition where the body has lost more water than it has taken in. Preventing dehydration matters because it helps the body cool itself, keeps blood volume steady and supports good performance. If you fail to replace lost water, dehydration develops and performance drops. So hydration is a preventive action: keep intake equal to loss and dehydration is avoided.

Dehydration means the body loses more water than it takes in, so body water falls below the level needed for normal function. In this specification the consequences you must know are: blood thickening (increased viscosity), which slows blood flow; a rise in body temperature and reduced ability to cool down through sweating; and a drop in performance, with earlier fatigue and poorer concentration. Link the chain explicitly: less plasma water makes the blood more viscous, slower flow reduces delivery of oxygen and nutrients to working muscles and slows removal of waste, so the performer tires sooner. Sweating during exercise in the heat is the usual cause, so the practical answer is to drink water before, during and after activity.

This clause names one specific consequence of dehydration: the blood thickens, which is described as increased viscosity, and this slows blood flow. Viscosity is a measure of how easily a fluid flows; more viscous blood is thicker and resists flow, so the heart must work harder to circulate it. Slower flow means oxygen and nutrients reach the working muscles more slowly and waste products are removed more slowly, so the performer fatigues sooner. Keep the causal order clear: water is lost through sweating, plasma volume falls, the blood becomes more viscous, flow slows, and delivery to muscles drops. The correction is to rehydrate with water before, during and after exercise.

This point sits inside the hydration part of the energy use, diet, nutrition and hydration topic. It lists three effects that dehydration can have on the heart: heart rate increases, the heart has to work harder, and the heart rhythm can become irregular. When the body loses fluid and is not rehydrated, blood volume falls, so the heart must beat faster and with more effort to keep blood and oxygen moving to the working muscles. These are consequences of dehydration, not simply the normal rise in heart rate that any exercise produces. In a multiple-choice question, read the stem to see whether it asks about a dehydrated performer; if it does, select the option describing a raised heart rate, greater cardiac effort or an irregular rhythm, and reject options that describe only ordinary exercise responses or unrelated dietary effects.

This row belongs to the diet, nutrition and hydration topic, which links what a performer consumes and how the body manages heat to safe performance. The statement names two connected ideas: body temperature rises during activity, and a performer can overheat if that rise is not controlled. Working muscles release energy, and only part of that energy does mechanical work; the rest appears as heat, so core temperature climbs. The body responds by sweating and by increasing blood flow to the skin so heat can be lost, which is why hydration matters: sweat losses must be replaced or the body struggles to cool itself. Overheating is the harmful end point, with symptoms such as dizziness, nausea and confusion, and it is more likely in hot conditions or when fluid is not replaced.

Dehydration and inadequate fuelling impair the brain as well as the muscles. When body water falls, blood volume drops and the heart must work harder, so less efficient delivery of oxygen and glucose to the nervous system slows the processing that turns what a performer sees into a movement. A games player may notice the ball arriving later than expected, take longer to choose a pass, and pick an option that looked sound in training but fails under pressure. Recognise the linked chain: fluid loss, reduced concentration, delayed signal handling, slower movement, weaker tactical choices. Revision should connect each stage to a sporting example rather than memorising a list, and should distinguish a slower response from a wrong response, because decision quality and reaction speed are related but not identical outcomes.

Fatigue and cramp are different problems with different causes, and a strong answer keeps them apart. Fatigue is the decline in a muscle's ability to keep producing force, often after prolonged activity when fuel stores fall and waste products build up; performance drops and technique deteriorates. Cramp is a sudden, painful involuntary contraction of a muscle, linked to fluid and electrolyte loss, especially sodium, and to fatigue or overuse. Both are common in endurance events and in hot conditions. Revision should pair each term with its cause, its sensation and its management: fatigue is managed by pacing, fuelling and rest, while cramp is managed by stopping, gently stretching the muscle and replacing fluids and electrolytes. Linking cause to remedy shows understanding rather than a memorised label.

Dehydration means losing more body water than is replaced, so blood volume falls and the body struggles to lose heat. Learners should understand the chain: sweating during exercise loses water and salts; if intake lags behind loss, plasma volume drops; heart rate rises, stroke volume and cardiac output fall, body temperature climbs and perceived effort increases. Performance consequences include earlier fatigue, slower reactions, reduced endurance and coordination, and greater heat-illness risk. Evaluation means judging how far these effects matter in different activities: a marathon runner sweating for over two hours is affected differently from a goalkeeper or a short explosive sprinter, and hot, humid conditions worsen losses. A strong answer links mechanism to activity demands and weighs severity rather than listing symptoms.