Health is all about making sure the body works properly. There are many ways to do this, because different parts of the body have different needs. For example muscles (including the heart) need a lot of exercise if they are to stay healthy. So you can either play a game or walk the dog or go cycling, for example.

The gut (the long channel from your mouth to your bottom) carries food in and waste out. It is kept healthy by having the right balance of bacteria and by having enough stuff moving along it. To keep stuff moving along and produce what doctor's call 'bowel movements', you need to eat foods with fibre in. Fibre is not digested, but acts rather like a chimney-sweep's brush, pulling out all other wastes as it moves down.

The liver and kidneys are kept healthy by drinking lots of water. They are damaged by lots of alcohol.

The body's tissues are kept healthy by eating a balance of foods, because no one food contains all of the materials we need to build new tissues.

The body's blood system is kept healthy by not eating too many fatty things, so that the arteries do not get blocked up.

The teeth are kept healthy by brushing and using toothpaste to remove plaque, which contains bacteria. This is helped by not eating too much sugar.

As you can see, it is a long and complicated list, but keeping healthy is easy to do: just make sure your body is kept active and eat a range of foods, don't sit about eating fatty foods.