Health, Fitness and Wellbeing: Diet, Energy Balance and Performance
Energy balance is the relationship between the energy a person takes in through diet and the energy they use through basal metabolic rate and physical activity, and it determines whether an athlete's diet supports, maintains or undermines their sporting performance.
Before you start
Make sure you're comfortable with these topics first:
Method
- Learn the energy balance equation in words: weight is stable when energy intake equals energy expenditure; a surplus causes weight gain; a deficit causes weight loss.
- Learn that energy expenditure includes basal metabolic rate (energy used at rest) plus energy used in physical activity, so a very active performer has a higher energy requirement than an inactive person of the same size.
- Learn that the amount of energy a performer needs, and the balance of carbohydrate, fat and protein within that, depends on their sport: higher training volumes generally need more total energy and more carbohydrate.
- For a calculation question, always show your working: state the equation you are using, substitute the numbers given, then state the answer with the correct sign (surplus/deficit) or unit.
- For 'explain' questions about energy balance and performance, link the imbalance (surplus or deficit) to a specific consequence, such as unwanted weight gain reducing speed, or insufficient energy intake limiting recovery and increasing injury risk.
- For an extended question, consider both directions of imbalance (too much and too little energy) rather than only describing the risks of one.
Worked example
A rower has a total daily energy expenditure of 3,400 kilocalories on a heavy training day, but eats food and drink providing 3,000 kilocalories that day. Calculate the size of this energy imbalance, state whether it is a surplus or a deficit, and explain one likely consequence if this pattern continued for several weeks.
- Set up the calculation: energy balance = energy intake - energy expenditure.
- Substitute the numbers: 3,000 - 3,400.
- Calculate: 3,000 - 3,400 = -400, so there is an energy deficit of 400 kilocalories on this day.
- Explain a likely consequence: if this deficit continued for several weeks, the rower's body would draw on its energy stores, which could lead to unwanted weight loss, reduced glycogen stores for training, and slower recovery between sessions.
Practice questions
Try each question, then tap to reveal the answer.
Q1What happens to a person's body weight if energy intake regularly exceeds energy expenditure?Show answer
Answer: Body weight increases, as the surplus energy is stored as body fat.
Q2What happens to a person's body weight if energy expenditure regularly exceeds energy intake?Show answer
Answer: Body weight decreases, as the body draws on its stored energy to make up the shortfall.
Q3What is basal metabolic rate?Show answer
Answer: The amount of energy the body needs at rest simply to maintain its basic functions, such as breathing and circulation.
Q4A cyclist expends 2,800 kilocalories in a day and eats food providing 3,100 kilocalories. Is this a surplus or a deficit, and by how much?Show answer
Answer: A surplus of 300 kilocalories (3,100 - 2,800 = 300).
Q5Why might a very active athlete need a higher daily energy intake than an inactive person of the same body size?Show answer
Answer: Because their total energy expenditure is higher, as physical activity adds to the energy used for basal metabolic rate.
Q6Explain why a boxer trying to make a specific weight category might deliberately create a short-term energy deficit.Show answer
Answer: A short-term energy deficit causes the body to draw on its energy stores, leading to weight loss, which can help the boxer reach the weight limit for their category before a competition.
Q7Give one performance risk of a performer regularly eating too little to fuel their training.Show answer
Answer: Insufficient energy intake can lead to poor recovery, reduced training quality, greater fatigue, or an increased risk of illness or injury.
Exam-style questions
Written in the style of a GCSE Physical Education exam paper, with a full mark scheme.
A gymnast has a daily energy expenditure of 2,200 kilocalories and eats food and drink providing 2,500 kilocalories. Calculate the energy imbalance and state whether it is a surplus or a deficit.
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Explain two consequences for a performer of consistently eating significantly more energy than they expend.
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Discuss the risks to a performer's health and performance of both a long-term energy surplus and a long-term energy deficit.
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See real GCSE Physical Education past-paper questions, with official mark schemes →
Free printable worksheet
Want more practice on paper? Download the health, fitness and wellbeing: diet, energy balance and performance worksheet pack - 10 pages of exam-style questions with a full mark scheme. One email opens every download in this browser for 14 days - no account, no card. Print it for personal and classroom use.
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