What makes a balanced diet, and how should nutrition support physical activity and a healthy weight?
The components of a balanced diet and their functions, the concept of energy balance and its link to body weight, and the dietary needs of people taking part in physical activity, including hydration.
A focused CCEA AS Sports Science answer on diet and nutrition, covering the components of a balanced diet and their functions, energy balance and its effect on body weight, the dietary needs of active people, and hydration.
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What this dot point is asking
CCEA wants you to know what makes up a balanced diet and the function of each component, to understand energy balance and how it controls body weight, and to describe how nutrition and hydration should support physical activity. Diet is central to both health and performance, so this topic links closely to lifestyle disease and to the effects of exercise.
Components of a balanced diet
A diet is balanced when these components are present in the right proportions for the person's age, sex and activity level. Carbohydrate makes up the largest share of energy intake for most active people, with moderate protein and limited saturated fat.
Energy balance and body weight
Three outcomes follow. When intake equals expenditure, body weight is stable. When intake exceeds expenditure (a positive energy balance), the surplus is stored mainly as fat and weight rises. When intake is less than expenditure (a negative energy balance), the body draws on its stores and weight falls. This is why a personal trainer designing a weight-loss programme combines a controlled intake with increased activity to create a negative balance.
Nutrition and hydration for active people
People taking part in physical activity have particular needs. They require enough carbohydrate to maintain glycogen stores and fuel exercise, especially before and after endurance activity. They need adequate protein to repair and build muscle in response to training. Above all they must stay hydrated: water is lost through sweat during exercise, and dehydration reduces blood volume, raises heart rate and body temperature, and impairs both performance and judgement. Drinking before, during and after activity restores the fluid lost.
Examples in context
Example 1. Creating a negative energy balance safely. A client who wants to lose weight is advised to reduce energy intake modestly (smaller portions, less added sugar and saturated fat) while increasing energy expenditure through regular exercise. This combination produces a sustained negative energy balance so that the body uses fat stores, while keeping the diet balanced enough to maintain health and training. It shows how the energy balance concept is applied in a real weight-management plan.
Example 2. Why iron matters for an endurance athlete. Iron is a mineral needed to make haemoglobin, the molecule that carries oxygen in the blood. An endurance athlete with too little dietary iron may develop anaemia, reducing the oxygen-carrying capacity of the blood and causing fatigue and poor performance. This illustrates how a micronutrient, needed only in small amounts, can have a large effect on an active person, which is why a balanced diet matters beyond just energy.
Try this
Q1. State the main function of carbohydrate and the main function of protein in the diet. [2 marks]
- Cue. Carbohydrate is the main energy source; protein provides amino acids for growth and repair.
Q2. Explain why hydration is important for someone taking part in prolonged exercise. [3 marks]
- Cue. Sweating loses water; dehydration lowers blood volume, raises heart rate and body temperature, and impairs performance, so fluids must be replaced.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA AS 20206 marksDescribe the main components of a balanced diet and state a function of each.Show worked answer →
Cover the macronutrients and at least one micronutrient group, with a function each.
Carbohydrates are the body's main and preferred energy source, especially for moderate and high-intensity exercise. Fats provide a concentrated energy store, insulate the body and protect organs, and supply energy for low-intensity, long-duration activity. Proteins provide amino acids for the growth and repair of tissues, including muscle.
Vitamins are needed in small amounts for many body processes, for example vitamin C for tissue repair and vitamin D for calcium absorption. Minerals such as calcium build bones and teeth and iron forms haemoglobin to carry oxygen. Fibre aids digestion and gut health, and water is needed for hydration, transport and temperature control.
Markers reward the three macronutrients with correct functions, plus at least one micronutrient group and water or fibre, each with a stated role.
CCEA AS 20174 marksExplain the concept of energy balance and how it affects body weight.Show worked answer →
Define energy balance, then explain each of the three outcomes.
Energy balance is the relationship between the energy taken in from food and drink and the energy expended by the body through its metabolism and physical activity.
If energy intake equals energy expenditure, body weight stays the same. If intake is greater than expenditure (a positive energy balance), the excess is stored, mainly as fat, and weight increases. If intake is less than expenditure (a negative energy balance), the body uses its stores for energy and weight decreases.
Markers reward a correct definition of energy balance and the three correct outcomes (maintenance, gain from positive balance, loss from negative balance).
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