What is Energy?

Energy is the ‘power’ that makes the body work. Every cell of our bodies needs energy to function.


What is energy made of?

Scientists measure energy in tiny units called ‘joules’. A joule is the amount of energy used to move an object one metre in one second. We can understand this more easily by knowing it is about the amount of energy we need to lift an apple one metre into the air.

Energy in food is measured in kilojoules (one kilojoule is 1000 joules) and megajoules (one megajoule is 1000 kilojoules). The term ‘calorie’ is also sometimes used to talk about the amount of energy in food. 1 calorie (Kcal) is roughly equivalent to 4 kilojoules (kJ). Countries using the metric system use kilojoules but others, for example the United States, use calories.

How much energy do we need?

People need different amounts of energy, depending on age, size, and activity levels. 

We need extra energy to:

  • Grow fast.
  • Recover from a serious illness.
  • Be very active.
  • Keep warm if it’s very cold.

How do we get energy?

We get energy from the food that we eat. Food is broken down in the digestive system and nutrients travel to where they are needed in the blood. We get most of our energy from carbohydrates, protein, and fat.

How do our bodies use energy from food?

Now you have read through our Fact Sheet, have a go at Harold's quiz below:

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