Macronutrients

Macronutrients are the nutrients the body needs in large amounts. The three macronutrients are carbohydrates, proteins and fats. For Edexcel GCSE PE, you must know the function of each macronutrient, the foods that provide it, the recommended proportions in a balanced diet, and how each relates to sporting performance.

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What Are Macronutrients?

"Macro" means large — macronutrients are needed in large quantities because they provide the body with energy and the building blocks for growth and repair.

Macronutrient	Primary Function	Energy per Gram
Carbohydrates	Main energy source	4 kcal
Proteins	Growth and repair of muscle tissue	4 kcal
Fats	Energy reserve, insulation, protection of organs	9 kcal

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Carbohydrates

Carbohydrates are the body's primary and preferred source of energy, particularly during exercise.

Types of Carbohydrates

Type	Description	Examples	Speed of Energy Release
Simple (sugars)	Small molecules; digested and absorbed quickly	Fruit, sweets, sugar, honey, energy gels	Fast — quick burst of energy
Complex (starches)	Large molecules; digested and absorbed slowly	Pasta, rice, bread, potatoes, oats, cereals	Slow — sustained energy release

How Carbohydrates Are Used in the Body

1. Carbohydrates are broken down into glucose during digestion
2. Glucose is transported in the blood to cells where it is used for energy
3. Excess glucose is stored as glycogen in the muscles and liver
4. During exercise, glycogen is converted back to glucose and used as fuel
5. If glycogen stores are full, additional carbohydrate is stored as fat

graph TD
    A["Carbohydrates Eaten"] --> B["Broken Down to Glucose"]
    B --> C["Used Immediately<br/>for Energy"]
    B --> D["Stored as Glycogen<br/>(Muscles & Liver)"]
    D --> E["Converted Back to Glucose<br/>During Exercise"]
    D --> F["If Stores Full:<br/>Stored as Fat"]
    style A fill:#f39c12,color:#fff
    style C fill:#27ae60,color:#fff
    style D fill:#1565c0,color:#fff

Recommended Proportion

Carbohydrates should make up approximately 55–60% of total energy intake.

Exam Tip: When discussing carbohydrates, always distinguish between simple and complex. The exam frequently asks which type is best before, during or after exercise.

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Proteins

Proteins are essential for growth and repair of body tissues, particularly muscle tissue.

Functions of Protein

Function	Detail
Growth and repair	Builds and repairs muscle tissue, especially after exercise
Enzyme production	Proteins form enzymes that control chemical reactions in the body
Hormone production	Some hormones (e.g. insulin) are proteins
Immune function	Antibodies that fight infection are made from protein
Secondary energy source	The body can use protein for energy if carbohydrate stores are depleted (not ideal)

Protein Sources

Animal Sources	Plant Sources
Chicken, turkey, beef, pork	Beans, lentils, chickpeas
Fish (salmon, tuna, cod)	Tofu, tempeh
Eggs	Nuts and seeds
Milk, cheese, yoghurt	Quinoa

Recommended Proportion

Proteins should make up approximately 15–20% of total energy intake.

Athletes involved in strength and power sports (weightlifting, sprinting, rugby) often consume more protein to support muscle growth and repair.

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Fats

Fats provide energy, particularly during low-intensity, long-duration exercise. They also serve important non-energy functions.

Functions of Fat