IGCSE PE 0413 · Area 2 · Health, Fitness & Training

Diet and Energy Sources

What you eat is the fuel every other system runs on. Cambridge asks you to match each nutrient to its job and to a food source, to explain whose energy needs are higher and why, and to say what happens to energy that is not used. Marks go missing in that last part, where students describe respiration but never mention glycogen.

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Syllabus coverage

  • The function of nutrients, including carbohydrates, fats, proteins and water
  • Examples of sources of these nutrients in food
  • The energy balance suitable for physical activities
  • Different energy needs for performers: males compared with females, teenagers compared with children, active lifestyles compared with sedentary lifestyles
  • Unused energy is stored as fat, which could cause obesity
  • Energy is derived from food sources: muscle cells release energy from glucose in a process called respiration; some glucose is converted to glycogen and stored in the muscles and liver

Part of the IGCSE PE 0413 syllabus 0413 / 0995.

A balanced diet: carbohydrate for energy, protein for repair, fat for stored energy and water for hydration.

The four nutrients and what they do

Cambridge names four nutrients: carbohydrates, fats, proteins and water. Each has a job in the body, and each job has a reason it matters to a performer.

A one-mark question usually asks for a function or a food source. Learn the function and the source together, in the same sentence, so you can answer either version without stopping to think.

NutrientFunction in the bodyFood sources
CarbohydratesThe body's main and quickest source of energy; digested into glucose, which muscle cells use to release energy in respirationBread, pasta, rice, potatoes, cereals, fruit, sugar
FatsA concentrated store of energy; also insulates the body, cushions and protects vital organs and carries fat-soluble vitaminsButter, oils, cheese, oily fish, nuts, red meat
ProteinsGrowth and repair of body tissue, including muscle; used as an energy source only when carbohydrate and fat stores run lowChicken, fish, eggs, milk, cheese, beans, lentils, nuts
WaterTransports nutrients and oxygen around the body, regulates body temperature through sweating, lubricates joints and is needed for the body's cells to workWater, milk, fruit juice, squash, fruit and vegetables
Every one of the four has a job as well as a food source. "Protein is in eggs" earns a source mark but not a function mark, and those are usually separate marks on the same question.

Energy balance: energy in against energy out

The energy in food is measured in kilocalories (kcal). Energy balance is the relationship between the energy you take in from food and the energy you use up in activity, growth and everyday living.

Three outcomes matter. If intake equals expenditure, body weight stays stable. If intake is higher than expenditure, the surplus is stored as fat and weight increases. If intake is lower than expenditure, the body uses its fat stores and weight decreases.

  • A performer in heavy training uses far more energy than a sedentary person, so energy intake has to rise to match it.
  • Too little energy intake and the performer runs out of fuel: they tire early, recover slowly and lose muscle as well as fat.
  • Too much energy intake over time and the performer carries extra weight, which makes every movement harder work.
Cambridge does not reward the phrase balanced diet on its own. Write which way the balance is tipped and what the consequence is for the performer.

Different performers, different energy needs

Energy needs are not fixed. Cambridge names three comparisons: males compared with females, teenagers compared with children, and active lifestyles compared with sedentary lifestyles.

ComparisonWhy the energy need is different
Males compared with femalesMales generally have a greater muscle mass and a larger body, so they use more energy and usually need a higher daily intake. Females generally have less muscle and a higher proportion of body fat, so their energy needs are usually lower.
Teenagers compared with childrenTeenagers are still growing and are usually larger and more active than children, so they need more energy. Growth itself uses energy, which is why an adolescent performer needs a higher intake than a younger child.
Active lifestyles compared with sedentary lifestylesAn active lifestyle means regular training and competition, so energy expenditure is high and intake must rise to match it. A sedentary lifestyle means little activity, so expenditure is low and a high intake would quickly be stored as fat.
Gender is only one factor. Activity level drives most of the difference, so an active female performer can easily need more energy than a sedentary male of the same age. Say that if the question invites evaluation.

From food to movement: respiration and glycogen

Energy is not used straight from the plate. Carbohydrate is broken down during digestion into glucose, which is carried in the blood to the muscles.

Inside a muscle cell the cell releases energy from glucose in a process called respiration. That released energy is what powers the muscle to contract.

Glucose that is not needed immediately is converted to glycogen and stored in the muscles and in the liver. When exercise begins and demand rises, the glycogen is converted back to glucose and used for energy.

  • Used now: glucose → energy released in the muscle cell (respiration).
  • Stored for later: glucose → glycogen in the muscles and liver.
  • The harder a performer trains, the faster glycogen is used up, which is why distance runners eat carbohydrates before a race.
Learn the two destinations of glucose as a pair. Questions regularly ask for both, and students who only write respiration throw away the glycogen mark.

Unused energy, fat storage and obesity

Any energy taken in but not used is stored as fat. Some fat is necessary: it insulates the body, cushions and protects vital organs and acts as a long-term energy store.

The problem is the amount. If energy intake regularly exceeds expenditure, body fat increases and this can lead to obesity — carrying an excessive amount of body fat for your height and build.

  • Extra body fat has to be carried, so the performer works harder to move and tires sooner.
  • It increases the strain on the joints and on the heart and lungs, and raises the risk of conditions such as type 2 diabetes and heart disease.
  • It reduces flexibility and makes temperature regulation harder, because fat acts as insulation.

Answering diet questions: name it, then say what it does

A state question wants the fact: "Water regulates body temperature."

An describe question wants the process in order: "Carbohydrate is digested into glucose, which is carried in the blood to the muscle, where the muscle cell releases energy from it in respiration."

An explain question wants the fact plus a consequence for the performer: "A rower needs a high carbohydrate intake so that muscle glycogen is replaced after training; if it is not replaced the rower tires early in the next session and cannot hold the stroke rate."

Sporting examples must come from the syllabus activity list. Use activities such as Association Football, Rowing and Sculling, Cross-Country Running, Competitive Swimming or Weight Training for Fitness.

Key terms you must be able to define

Nutrient
A substance in food that the body needs to work properly. The syllabus names carbohydrates, fats, proteins and water.
Carbohydrate
The nutrient that is the body's main and quickest source of energy, digested into glucose.
Fat
A nutrient that is a concentrated store of energy and also insulates the body, protects vital organs and carries fat-soluble vitamins.
Protein
The nutrient used for growth and repair of body tissue, including muscle; only a minor energy source.
Water
The nutrient that transports nutrients and oxygen, regulates body temperature, lubricates joints and is needed by every cell of the body.
Energy balance
The relationship between the energy taken in from food and the energy used by the body in activity, growth and everyday living.
Glucose
The simple sugar produced when carbohydrate is digested. Muscle cells release energy from glucose by respiration.
Respiration
The process by which muscle cells release energy from glucose.
Glycogen
The storage form of glucose, held in the muscles and the liver and released for energy when demand rises.
Obesity
The condition of carrying an excessive amount of body fat, caused by energy intake regularly exceeding energy expenditure.
Sedentary lifestyle
A lifestyle with little or no physical activity, so energy expenditure is low.

Applied to your sport

Cambridge requires you to apply this knowledge to physical activities. Use these as models, then write your own for the sport you play.

Track and Field Athletics

A sprinter eats a carbohydrate-rich meal before racing because carbohydrate is digested into glucose, which the muscle cells use to release energy for an explosive 100 m.

Cross-Country Running

A distance runner needs a high carbohydrate intake to keep muscles and liver topped up with glycogen; once the glycogen runs low the runner slows and cannot hold the pace.

Rowing and Sculling

A rower needs protein to repair muscle after long sessions and an energy intake large enough to match the energy used in training — otherwise they lose weight and lose power in the stroke.

Competitive Swimming

A swimmer still sweats and loses water during a long session, so they drink before and during training. Dehydration reduces performance and makes temperature regulation harder.

Weight Training for Fitness

A performer who eats more energy than they use in the gym will store the surplus as fat, not muscle: excess energy is never turned into muscle.

Flashcards

Click a card to flip it. Mark honestly — the tracker uses this.

Q1State the four nutrients named by the syllabus.
Carbohydrates, fats, proteins and water.
Q2What is the function of carbohydrate?
The body's main and quickest source of energy; digested into glucose, which muscle cells use to release energy in respiration.
Q3Give two food sources of protein.
Any two of: chicken, fish, eggs, milk, cheese, beans, lentils, nuts.
Q4What is energy balance?
The relationship between the energy taken in from food and the energy used by the body.
Q5What happens if energy intake regularly exceeds energy expenditure?
The unused energy is stored as fat, body fat increases and this can lead to obesity.
Q6How do the energy needs of a teenager differ from those of a child?
A teenager needs more energy because they are growing and are usually larger and more active; growth itself uses energy.
Q7How do the energy needs of an active performer differ from those of a sedentary person?
The active performer uses far more energy in training and competition, so needs a higher intake; the sedentary person has low expenditure and needs less.
Q8Why do males generally need more energy than females?
Males generally have a greater muscle mass and a larger body, so they use more energy at rest and during activity.
Q9What happens to glucose inside a muscle cell?
The muscle cell releases energy from it in a process called respiration.
Q10Where is glycogen stored?
In the muscles and in the liver.
Q11Name one function of water in the body.
Transporting nutrients and oxygen around the body (also: regulating body temperature through sweating, lubricating joints).
Q12Give a sporting reason why dehydration lowers performance.
Water regulates body temperature, so without enough of it a performer overheats and tires faster; water also transports the nutrients and oxygen the muscles need.
0 of 12 marked as known

Exam-style questions

6 questions, 17 marks. Write your answer, then reveal the mark scheme and tick each point you actually made. Answering honestly here is what makes the rest of the site useful.

StateAO11 mark
State one function of water in the body.

Mark scheme — tick each point you actually made

Examiner tip: One mark, one function. Do not list four and hope; give one clear function and move on.
IdentifyAO12 marks
Identify two food sources of protein.

Mark scheme — tick each point you actually made

Examiner tip: Name foods, not food groups. Two named foods is two marks; 'protein foods' is zero.
DescribeAO12 marks
Describe how energy is released from food inside a muscle cell.

Mark scheme — tick each point you actually made

Examiner tip: Two marks means the journey and the process. Students who write only 'respiration' gain one of the two.
ExplainAO23 marks
Explain why a rower in heavy training has a higher energy requirement than a sedentary person of the same age.

Mark scheme — tick each point you actually made

Examiner tip: Each mark needs a reason. Name the demand (training), the consequence (tiring early) and the storage form (glycogen).
ExplainAO24 marks
Explain why a 16-year-old performer needs more energy than a 10-year-old child, and what happens to any energy that is not used.

Mark scheme — tick each point you actually made

Examiner tip: This question is split into two jobs. Do both — two marks for the comparison, two for the storage point.
EvaluateAO25 marks
A coach says: 'Males generally need more energy than females, so a male performer can always eat more than a female performer.' Evaluate this statement.

Mark scheme — tick each point you actually made

Examiner tip: Evaluation needs both sides plus a judgement. Give the argument, the counter-argument and a final line that weighs them.

Exam technique for this topic

  • Read the command word. State wants the fact, describe wants the process step by step, explain wants the fact plus the consequence for the performer.
  • If the question asks for a food source, name a food, not a food group. Chicken scores; meat is weak; a balanced diet scores nothing.
  • Do not write a balanced diet on its own. Say what is balanced against what, and what happens if it is not.
  • For a different energy needs question, name the two groups and give the reason — body size, muscle mass, growth or training load. A reason-free comparison caps your marks.
  • Keep glucose's two fates as a pair: energy released now by respiration, or stored as glycogen in the muscles and liver.

Why students lose marks here

A student wroteCarbohydrates give you energy and protein gives you energy too.
Why it loses marksBoth are energy sources, but the answer never explains what makes carbohydrate different or what protein is actually for, so it stops at one vague mark.
The answer that scoresCarbohydrate is the body's main and quickest source of energy: it is digested into glucose, which muscle cells use to release energy. Protein is used for growth and repair of tissue such as muscle, and supplies energy only when carbohydrate and fat stores are low.
A student wroteUnused energy is turned into muscle.
Why it loses marksExcess energy is stored as fat, not muscle. Muscle is built from protein and from training, never from surplus kilocalories.
The answer that scoresUnused energy is stored as fat. If energy intake regularly exceeds expenditure, body fat increases and this can lead to obesity.
A student wroteFemales need less energy than males, so they should just eat less.
Why it loses marksToo absolute, and it gives no reason. Energy need depends on training load as much as on gender, and the question wants the cause of the difference.
The answer that scoresFemales generally have a smaller muscle mass and a higher proportion of body fat than males, so their energy needs are usually lower. An active female performer can still need more energy than a sedentary male, because training is the biggest factor in energy expenditure.
A student wroteGlucose that is not used straight away is stored in the muscles as fat.
Why it loses marksWrong storage form. Fat is the storage form of unused energy overall; glucose specifically is stored as glycogen.
The answer that scoresSome glucose is converted to glycogen and stored in the muscles and in the liver, ready to be released for energy when demand rises.

Where this fits in IGCSE PE 0413

This page is one topic of Cambridge IGCSE PE 0413 / 0995. IGCSE PE 0413 is the course home: every area and every topic in Cambridge's own order, the papers you sit and what each one tests, and the exam-practice tools. The full topic list, with each topic linked to its revision page, is on the IGCSE PE 0413 syllabus page.