The most important thing to any of us is a healthy body. Healthy bodies allow us to live longer, we are less of a burden on our loved ones and we cost the state less in terms of health care. Sounds pretty boring? Well, if you are ever ill, you know that life becomes very miserable. We can't avoid being ill sometimes, but we can certainly understand why it happens and so help to do some things that keep us healthy for longer. One of those is to watch our diet.

Why the body needs food
The body is made from cells. Trillions of them. Some are joined up to make solid things like bones, others make flexible things like skin, and some are floating about loose in our liquids, such as blood. When you are born, you are tiny. Over the years you get bigger, and this means more cells are needed. You don't die with the cells you were born with. Every single cell in your body has a short life. You don't notice this because cells are dying off and new one replacing them all the time. Here are some examples: when you cut yourself, you don't stay cut, the cut heals over. It uses new cells to do that. When you vacuum the floor you pick up dust, but much of that dust is skin that has flaked off your body. It is simply old skin cells dropping off as new ones grow to replace them. Look in a dust bag of a vacuum cleaner some time and see how much we lose: it's quite a lot.

These cells don't grow out of thin air. They have to be made of something. Cells can't grow out of solid materials either. They can only grow in liquids. That is one reason our bodies are nearly all water. Water is an amazing liquid that can carry other materials around, and that lets all kinds of materials come and go from it. If your food and drink were cut off, the reason you would die is not from starvation, but from loss of water. We call it dehydration. It would happen within a few days. On the other hand, your body's store of food would last for many weeks.

Actually here is the first thing to notice. Our bodies are like amazing chemical sets. Everything that goes on uses water. So this is the most important thing our body needs and why we should drink water all the time. Lots of it. It is actually part of your diet. Diet is not just about food.

But before we go on, let's just remember that a few thousand years ago we were surviving by gathering foods from wild forests and grasslands. We weren't going to the shops. It is hard work finding sufficient food to eat when you have to search for it. Your senses, especially your taste buds in your tongue, are your only guide. There are taste buds that tell you when you have found something sweet, like honey. The body needs sweet things because they are packed with materials that will dissolve easily in water and which contain many building blocks for cells, as well as energy to allow the cells to move. That is why we are attracted to sweet things – sweet things have been partly worked at by some other living thing (such as bees and some plants) and so they are easy for us to use. But in the wild we only find honey occasionally. So we don't get too much of it.

Now no one in the past had to worry much about all of these properties of food. But over millions of years we have become adapted to extract and use all of these raw foods. So what we have to keep in mind is that we might now live indoors and watch computers, but our bodies still think they are in the wild forests.

As you can see, natural foods contain all kinds of things we need that work in all kinds of ways. That is what the body was adjusted to in the wild. If we start altering the food by taking out some things, we often cause problems elsewhere, and if we eat processed things, we often find they have been made with fat (such as oil) and so we can end up putting too much fat into our bodies.

People in the wild all used to have what is called a 'balanced diet'. No one knew it was balanced, they just ate what they could get hold of. As different things grow in different parts of the world, people ended up with quite different kinds of foods. But they all did the same things: gave energy, vitamins, substances to build cells, and fibre to remove waste. And they all had to work hard to feed themselves, so the blood went pounding around the body, sweeping waste products away, too.

This is the reason no one part of the world naturally has a better or worse diet than any other part. But some parts of the world have ended up liking a set of meals that are still more balanced that others. Let's take the example of Mediterranean foods. Now more or less everyone likes pizza - that's a Mediterranean food. But it is a very interesting food. It is mostly rolled-out dough. That was always easy to get becaue it is just flour and water. On it was sprinkled things like sausage and cheese - the tastes were there, but the quantities were small. Then there was the base flavouring – the red stuff on the pizza and under the toppings. That is made with tomatoes and olive (vegetable) oil. So most of it is dough (which fills you up, and breaks down slowly so it makes you feel full for longer) and it has the sweet, sour and salty flavours that your tongue wants.

Quite often people tended to use low fat cheese, like Greek feta cheese: very flavoursome, but with half the fat of some other cheeses. They also ate salad with it, olives and so on, giving lots of vitamins and fibre.

Now you can ruin the balance by having lots of toppings and changing to a high fat cheese like cheddar, which is what often happens in restaurants. But a thin crust pizza with flavoursome toppings in limited amounts (for example vegetarian pizza) with a side of salad, is good news. But you still have to get off your bum afterwards and work up a sweat to get all the chemicals going that will make nice new cells with all that pizza. And that is why you walk the dog, cycle, play football and so on. But if you don't care for sport, you don't have to do it. Digging the garden or doing the lawn mowing for an elderly neighbour will work off the surplus energy and be as good for you as sport, and do some good for your community as well.