What are calories?

Calories (kcal) are the basic units used to measure the energy values of foods. We get calories from carbohydrates, fat and protein. Eating too many calories too often can be unhealthy because when you cannot use all the energy stored in the food you eat, it is eventually stored as fat in your body. However, eating fewer calories than your body needs to function effectively can also be harmful to health.

Where does energy come from?

Energy comes from the sun and is called solar energy. Living plants are able to convert solar energy to chemical energy by a process called photosynthesis. The chemical energy is used to make other substances such as carbohydrate, fat and protein. Humans (and animals) cannot use solar energy directly but can use energy contained in food (either plants or other animals). Our bodies use the carbohydrate, protein and fat to produce energy, carbon dioxide and water.

Why do we need calories?

Our bodies need calories to function properly - i.e. to stay alive, grow, keep warm and be active. Children also need calories from a variety of foods to grow and develop.

Do calories make us fat?

Calories will only make you fat if you eat more than your body needs. Leftover calories that the body does not require will convert to fat unless they are burnt off through activity. Women need approximately 2000kcal a day and men need approximately 2500kcal. If you consistently take in more calories than you burn, you will gain weight. Whilst if you consistently take in fewer calories than you burn, you will lose weight.

How to burn calories

Some calories are burnt just by being alive - such as when we sleep, during general movement, and by eating, digesting, and absorbing food. Calories are also burnt through exercise such as walking or swimming.

You can speed up the rate of burning calories through high intensity exercise - this can help you burn more calories at the time and for several hours afterwards. You can also work to increase the amount of muscle in your body - muscle burns more calories than other body tissues, even when you are not moving.