KS3 · Biology

A balanced diet

Every part of your lunch has a job to do inside you. One part does its job without your body ever absorbing it. Which one, and why bother eating it?

Biology · Nutrition

Who does which job?

Your body has jobs that need doing. Pick a job, then put it under the part of your diet that does it.

Still to sort

Carbohydrates (0)

Rich sources: bread, rice, pasta, potatoes

Where the line is: Lipids can provide energy too, but carbohydrates are the body's MAIN fuel. Lipids are the back-up.

Lipids (fats and oils) (0)

Rich sources: butter, oil

Proteins (0)

Rich sources: meat, fish, beans, tofu, peas

Vitamins (0)

A wide range comes from fruit and vegetables

Where the line is: Vitamins and minerals share a job: both keep cells healthy. To tell them apart, look for the particular job.

Minerals (0)

A wide range comes from fruit and vegetables

Dietary fibre (0)

Rich sources: fruit, vegetables, whole grains

Water (0)

You lose it all day, in breath, sweat and urine

12 of 12 still to sort.

No column ends up empty. Every component of a healthy diet earns its place, including fibre, which the body never absorbs.

Carbohydrates · from potato to muscle

?

Reason it through

How does eating a potato end up moving your muscles?

Link 1 of 4

First link · your turn

A potato is full of starch, which is a carbohydrate. What happens to that starch inside your body?

2
Locked — reveal the link above first
3
Locked — reveal the link above first
4
Locked — reveal the link above first

Vitamins and minerals · up close

Four nutrients, five facts

Tick every fact that is true of each nutrient, then check your grid.

Vitamin D
Vitamin C
Iron
Calcium

Predict, then check

Think about what protein, fat and carbohydrate are each FOR.

Maya is 13, still growing, and plays football almost every day. Her uncle is 45, has stopped growing, and spends most of his day sitting down. Who needs more protein, fat and carbohydrate?

Food myths

Which idea holds up?

Five friends are arguing about food at lunch. Only one of them has it right.

Which idea is closest to what you think right now?
How sure are you?

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

What you need to know

  • The seven components of a healthy diet: carbohydrates, lipids (fats and oils), proteins, vitamins, minerals, dietary fibre and water.
  • The job each component does in the body, and a food that is rich in it.
  • Why dietary fibre is not a nutrient, but is still needed.
  • What a balanced diet is, and why different people need different amounts of nutrients.

The big picture

A healthy diet contains seven components: carbohydrates, lipids (fats and oils), proteins, vitamins, minerals, dietary fibre and water. Each one does its own job in the body. A balanced diet contains all of them in the right proportions, and different people need different amounts depending on their stage of life and lifestyle.

Key points

1A healthy diet has seven components: carbohydrates, lipids (fats and oils), proteins, vitamins, minerals, dietary fibre and water.
2Carbohydrates are the main fuel. Starch (for example in potatoes) is broken down into sugars, which the body uses to provide energy for processes such as muscle contraction.
3Lipids insulate the body to help keep it warm, act as a secondary energy source and energy store, and are needed to make cell membranes.
4Proteins are needed for growth and for repairing damaged tissue. They are not the body's main source of energy.
5Vitamins and minerals keep cells healthy. Vitamin D and calcium are needed for strong bones and teeth, vitamin C supports wound healing, and iron is needed to make red blood cells.
6Dietary fibre is not a nutrient because the body doesn't break it down and absorb it, but it adds bulk to food and helps move food through the gut.
7Water keeps the body hydrated and is needed for many chemical reactions. Water lost in breath, sweat and urine must be replaced.
8A balanced diet contains all the food groups in the right proportions. Different people need different amounts depending on their stage of life and lifestyle.

Worked example

Problem

Priya's lunch is a jacket potato with beans and butter, an apple, and a glass of water. Can you find all seven components of a healthy diet in it?

⚠ Watch out

Saying protein is the body's main energy source. Protein is for growth and repair; carbohydrates are the main fuel, and lipids are a secondary energy source and energy store.

🧠

Memory hook

FUEL, FIX, WRAP, KEEP WELL, PUSH, TOP UP. Carbohydrates fuel you, proteins fix you (growth and repair), lipids wrap you (insulation and cell membranes), vitamins and minerals keep your cells well, fibre pushes food through your gut, and water tops you up.

✓

Check yourself

Cover the page. Name all seven components of a healthy diet and give one job for each. Then explain, in one sentence, why fibre is needed even though it isn't a nutrient.

Flashcards

(15)
What are the seven components of a healthy diet?
Carbohydrates, lipids (fats and oils), proteins, vitamins, minerals, dietary fibre and water.
Which component is the body's main fuel?
Carbohydrates. They provide energy.
What happens to the starch in a potato so the body can use it?
It's broken down into sugars, which the body uses as a fuel for processes such as muscle contraction.
Give three jobs of lipids (fats and oils).
Insulation to help keep the body warm; a secondary source of energy and an energy store; making cell membranes.
What are proteins needed for?
Growth, and repairing damaged tissue. Protein is not the body's main energy source.
Vitamin D: why is it needed, and where does it come from?
Strong bones and teeth and a healthy immune system. It comes from oily fish and egg yolks, and the skin makes it in sunlight.
Vitamin C: why is it needed, and where does it come from?
It keeps the body healthy and supports wound healing. It's found mainly in fruit and vegetables.
Iron: why is it needed, and where does it come from?
To make red blood cells, which carry oxygen around the body. It's found in red meat and green leafy vegetables.
Calcium: why is it needed, and where does it come from?
To maintain strong bones and teeth. It's found in dairy products and green leafy vegetables.
Why isn't dietary fibre a nutrient?
The body doesn't break it down and absorb it.
Why do we still need fibre?
It adds bulk to food and helps move food through the gut, keeping the gut healthy. Fruit, vegetables and whole grains are rich in it.
Why does the body need water?
To stay hydrated and for many chemical reactions. Water lost in breath, sweat and urine has to be replaced.
What is a balanced diet?
A diet containing all the food groups in the right proportions. It's needed for good health of body and mind.
Why don't all people need the same amounts of each nutrient?
Needs change with stage of life and lifestyle. For example, a pregnant woman needs extra protein.
Does each food contain just one food group?
No. Foods usually contain a mix. A 'carbohydrate food' like bread is one that's rich in carbohydrate.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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How this lesson was checked. This KS3 Biologylesson was published through Lightbulb Learning's human-designed editorial process — the educational standards, accuracy rules and publication checks it must pass were authored and approved by Philip Halpin. It passed subject-specific assessment, automated educational checks and technical publication verification before going live (publication checks completed 30 September 2026). Published pages are monitored, human spot-checking is ongoing across the lesson library, and anything found wrong is corrected or withdrawn. How our lessons are made and checked. Spotted a mistake? Email hello@lightbulblearning.co and we'll review it.