How does the energy we eat balance against the energy we use, and what decides a healthy weight?
Energy use, the concept of energy balance (energy in versus energy out), how energy requirements vary, and the effect of energy balance on body weight, including the calculation of energy values.
A focused answer to OCR GCSE PE Component 02 on energy use and energy balance: the meaning of energy balance (energy in versus energy out), how energy requirements vary with age, sex and activity, the effect of energy balance on body weight, and calculating energy values from the macronutrients.
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What this dot point is asking
OCR wants you to explain energy use and energy balance (energy in versus energy out), how energy requirements vary, the effect of energy balance on body weight, and how to calculate energy values from the macronutrients.
Energy use (expenditure)
The body's energy is supplied by food, measured in kilocalories (kcal) or kilojoules. Different foods supply different amounts of energy per gram.
Energy balance
How energy requirements vary
Energy requirements vary with age (growing teenagers and active young adults often need more than older adults), sex (males generally need more than females, partly due to greater muscle mass), and especially activity level. An endurance athlete in heavy training may need far more energy than a sedentary office worker, so their food intake is higher, but it must still balance their (much higher) energy expenditure to keep their weight stable.
Calculating energy values
Why energy balance matters
Energy balance ties together diet and activity. A balanced diet (the previous topic) must supply the right amount of energy for the person's activity level, and a sedentary lifestyle (covered earlier) tips the balance towards storing fat because energy out is low. Understanding energy balance explains both how athletes fuel heavy training and why inactivity combined with overeating leads to obesity.
Exam-style practice questions
Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
OCR 20193 marksExplain what is meant by energy balance and what happens to body weight if energy intake is greater than energy expenditure.Show worked answer →
A Component 02 item on the energy-balance concept.
Award marks for: energy balance is the relationship between the energy taken in (from food and drink) and the energy used (expended) by the body. The body is in balance when energy in equals energy out, so body weight stays the same.
If energy intake is greater than energy expenditure, the excess energy is stored as fat, so body weight increases. Over time this can lead to overweight and obesity.
Markers want the energy-in-versus-energy-out definition plus the clear consequence (excess stored as fat, weight gain).
OCR 20214 marksA meal contains 60 g of carbohydrate and 10 g of protein. Carbohydrate provides about 4 kcal per gram and protein about 4 kcal per gram. Calculate the total energy in the meal and explain how this links to energy balance.Show worked answer →
A calculation item. Award marks for the working, the total and the link.
Energy from carbohydrate: kcal. Energy from protein: kcal. Total energy: kcal.
Link to energy balance: this 280 kcal is part of the day's energy in. If the person's total energy in over the day equals their energy out, their weight stays the same; if it is higher, the excess is stored as fat and they gain weight.
Markers want the two products, the total of 280 kcal, and a sentence linking the figure to energy balance.
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Sources & how we know this
- OCR GCSE (9-1) Physical Education J587 specification — OCR (2016)