Why do people need energy? - KS2 - BBC Bitesize (2024)

Article created in partnership with the British Nutrition Foundation.

Food and drinks, except water, act as ‘fuel’ for the body because they provide energy.

We need energy for everything we do.

We need energy to function, for example, to keep our heart beating, to breathe, grow, blink and think.

We also need energy to be active, for example, to move, play, run and do sports.

Energy from food and drinks is measured in .

Another unit we can use to measure energy in is . People often shorten kilocalories to ‘calories’.

Kilojoules is the metric measurement for energy. Other metric units of measurement are centimetres, metres and kilometres.

Kilocalories is the imperial measurement. Other imperial units of measurement are inches, feet and miles.

A food label usually shows the amount of energy in a food.

The energy information is shown per 100g of a food. Using per 100g makes it easier to compare the amount of energy in different foods.

Some food labels also show how much energy is in a serving. The serving is the amount of the food we are recommended to eat.

Here is a food label for wholemeal bread. The label shows the amount of energy in 100g of bread and in one slice of bread.

It also shows the amount of fat, carbohydrate, fibre and protein in 100g and one slice of the bread.

This slideshow shows the energy in kilojoules for 100g of different foods.

Can you spot which type of food provides the most energy per 100g?

Some foods are higher in energy than other foods.

For example, foods that contain fat are usually 'high' in energy. These include oil, butter, nuts and chocolate.

Fruit and vegetables are usually 'low' in energy.

We need to eat a smaller amount of foods that are high in energy.

This is to make sure that the rest of our energy, and all the different that we need, can come from a variety of other foods.

To find out more about nutrients, take a look at What are nutrients?

It is useful to look at the energy in 100g of different foods to help us to compare them, but we don’t eat 100g of all foods.

If we have a smaller or larger amount of a food, the energy it provides changes.

For example, 100g of butter provides 3,062 kJ of energy. However, a serving of butter is around 10g.

10g of butter provides 306 kJ of energy.

Different people need different amounts of energy.

The amount of energy someone needs each day depends on their age, if they are male or female and how active they are.

Different activities use different amounts of energy.

Here are some examples of the amount of energy a child in primary school would roughly use doing different activities for 15 minutes.