Energy foods
How is your body using energy right now? In the middle of your chest your heart is beating. With each beat, the heart pushes the blood around your body. In the sides of your chest some muscles are becoming tight. When they do this the sides of your chest lift upwards and outwards. This change makes you breathe in air. A few moments later the muscles become slack again and you breathe out. The beating of your heart and the movement of your chest muscles are just two of the ways your body is using energy.

Have you had a meal recently? If you have, your stomach and intestines will be digesting your food. As you look at the screen, your nerves are using energy to send messages from your eyes to your brain. The skin all over your body is slowly rubbing off onto your clothes and the furniture around you. Underneath, energy is being used to make new skin. Energy is also being used to make new bones and muscles to help you grow. In every part of your body energy is being used to make heat to keep you warm. Your body is using energy in many different ways every moment of your life.

It can help to understand about energy and food by thinking about a car and its petrol. The petrol is like the car's food. It gives the car energy. The car does not use the energy to grow or repair its damaged body. The car uses the energy in its engine to turn its wheels and move along. The petrol is stored in a petrol tank. The energy in a full tank of petrol can make the car go hundreds of kilometres. A substance, like petrol, which contains large amounts of energy, is called a fuel.

You can think of a car and its petrol as being like you and some of your foods. You need energy to work your muscles so they can move your arms and legs about when you walk or run. You take in energy when you have a meal just as a car does being filled up with petrol at a petrol station. There is a difference between the fuel you use and the fuel a car uses. Your fuel is not just one liquid. It is a number of different solids and liquids. The most common fuel you use is starch. It is a white substance and it is found in potatoes, rice and flour. It does not taste sweet but inside your body it is changed into a sugar. Another common fuel you take in is sugar. This may be as solid crystals sprinkled on corn flakes or dissolved in a sugary fizzy drink. The third fuel you take in is called fat. It is the white substance you find on meat such as lamb and beef. This substance is not used quickly by the body but stored under the skin. Here, it helps to keep your body warm like a blanket but if other fuels are in short supply your body will use it up.

When you are choosing foods for energy you must choose carefully. Two of the fuels can cause problems. Too much fat increases the body weight and makes the heart work harder. In time, this can make the heart unhealthy. Too much sugar can cause two problems. It can damage the teeth and is so high in energy that some of it may be stored as fat, which can affect the heart. Starchy foods such as potatoes, rice, bread and pasta are a healthier choice. The starch does not damage the teeth and the foods are not so high in energy that they make fat. Next time you have a meal look at your food. Check you are eating plenty of starchy food and very little fat and sugar.

Why does the body store high-energy food as fat?
It stores high-energy food as fat because there is simply too much energy for the body to use. The amount of energy a body needs depends on what it is doing. If you are asleep you only use a little energy to keep your body alive. It is like a car stopped at the traffic lights. The engine is still using a little energy in the petrol to keep it 'ticking over'. During the day, when you are out playing and running around, your body is using a large amount of energy. It is like a car that is racing along a motorway using large amounts of energy in its petrol. One difference between you and a car, is that the petrol tank will only hold a certain amount of petrol, while your body can keep or store as much energy as it likes. If the car is not used for a few days and more petrol is added, the tank simply overflows. If a person has a restful few days and yet still eats foods containing a large amount of energy that energy is changed into fat.

Is there fat in other foods besides meat?
Yes, there is. You can find large amounts of fat in some kinds of crisps. So eating a few bags of crisp a day can make the body put on extra weight it does not need. There can be a large amount of fat in fish and chips as the batter and potatoes soak up fat as they are frying.

Is eating fatty foods dangerous?
Not if only small amounts are eaten. All foods such as fish and chips are perfectly healthy provided that the diet does not contain a lot of fatty foods. A meal containing fatty food should be a special meal like a treat rather than a meal that you have every day. Eating meals which are high in fats every day can lead to a person becoming overweight and unhealthy.

Why do you need energy to keep you warm?
The human body needs to be kept at a certain temperature to keep healthy. This temperature is 37°C. If the body gets too hot or too cold, life could be in danger. Your body can help keep the temperature steady by sweating and shivering. You sweat when you are too hot and this cools you down. You shiver when you are too cold and this warms you up.

Do all animals keep their bodies warm like us?
Only mammals and birds. All the other animals such as insects, snails, fish and frogs let the temperature of the body change with their surroundings. It is quite safe for them to do this.

Where does sugar come from?
There are two main sources of sugar. They are the sugar cane and the sugar beet. The sugar cane is a huge kind of grass plant that grows in the warmer regions of the world. Its stem can grow up to five centimetres thick and over four metres tall. The sugar cane makes the sugar in its leaves and stores it as a sweet tasting sap in its stem. When the stem is cut down it is squashed to remove the sugary sap. The sugar beet grows in cooler regions of the world such as Great Britain. It makes sugar in its leaves and stores the sugar in a root, which is like a large fat purple carrot.

Do all plants make sugar in their leaves?
Yes, they do, but it is not the sweet tasting sugar that the sugar cane stores. The type of sugar made in leaves is called glucose. Most plants change this sugar into a substance called starch. They do it because it takes up less space to store starch than it does to store glucose. Plants can store starch in their leaves, roots and seeds. Trees store it in their wood.