A healthy digestive system generally doesn't cause problems, so most of us don't even think about what is happening to our insides.

We hear the odd rumble or gurgle, or we may occasionally suffer from wind coming up (belch) or going down (flatulence). But in fact these are only tiny parts of the constant conversation that our digestive system has with other parts of the body, particularly our brain.

The function of the digestive system is simplified in chapter one of a book about a diet that focuses on this vital part of our bodies.

Our digestive system is a bit like a miniature factory,' it says. Basic materials go in at one end, they are processed, the flow rate is controlled, products are created and diverted to one side, other things are added, yet more products are diverted to the side, and finally a residue passes out at the end.' And, like a factory, if the starting material or the equipment isn't quite right, the entire production chain is affected and can potentially break down.

For example, if the starting material (food) doesn't contain enough fibre, this means our production line has to work overtime to pass the waste out of the body and may sometimes give up for a while, resulting in constipation.

The gut's main function is to take in and process food in order to provide the body with energy (calories) and nutrients.

It also handles some substances made in the body such as cholesterol and bile salts, and provides an environment for the growth of friendly' bacteria needed for good health.

Unlike most diets which focus on weight loss, food types and calorie content, The Inside Out Diet - a diet and lifestyle plan devised by a panel of experts in the fields of health, diet and fitness - aims to improve, maintain and protect the health of the gut to improve health and wellbeing.

Statistics show that more than a third of the population claim to have problems with their digestive system. Doctors are diagnosing more people each year with irritable bowel syndrome (IBS) and colitis. And bowel cancer is the second-biggest cancer killer in the UK.

Even people who have a healthy diet can experience digestive problems, because the balance of bacteria in the gut is affected by a wide variety of everyday factors. It is well known that a hectic lifestyle can upset the health of our gut, in particular stress, inactivity, too much alcohol, a poor diet and lack of sleep.

The 60-page diet booklet contains advice on every aspect of life, including healthy eating, weight management, lifestyle, travel and exercise.

  • The Inside Out Diet is available free (usual price £3.49) from www.insideoutdiet.co.uk or by calling 0845 7697069 (local rate).

Case study

As manager of a busy nightclub, Jane Magill is always on the go.

She commutes from her Pudsey home to work in York, and rarely gets chance to put her feet up.

For a long time, Jane, 28, had felt that she lacked energy. She wanted to change her lifestyle but did not want to go on a conventional weight-loss diet.

"I had been on diets before but gave up on them. I wasn't really looking to lose weight, just to feel fitter and more motivated."

A friend told her about the Inside Out Diet, so she gave it a try. After three months, She can't believe how much better she feels.

"I'm prone to food intolerances and the diet has taught me discipline with food and which foods to eat to stay healthy.

"I haven't been eating as many refined carbohydrates. I have cut these out and replaced them with fresh fruit and vegetables."

Jane discovered that although she did exercise, she was not doing enough. But through eating the right foods, she felt more inclined to exercise. "I felt less energetic before, now I've got a lot more get-up-and-go, so I visit the gym more often."

She stressed the importance of probiotic drinks and yoghurt, and foods such as greens and fruit, which help to stimulate the growth of these good bacteria - known as prebiotics.

"The diet taught me that you need healthy bacteria for your gut," says Jane, "My stomach used to regularly feel bloated - that has gone."

Although Jane did not set out to lose weight, she has dropped from a size ten to a size eight. "I feel lighter and much healthier."