It's your birthday. But as you blow out the candles on the cake your heart sinks - another year, another step towards old age.

But it doesn't have to be like that and a new book insists you can take control of your life to look and feel younger.

Leslie Kenton, author of Age Power, says age is more about health and vitality than the ticking of the clock.

"Forget your birthday," she says, " it's not chronological age that matters but biological age."

Biological age is measured by ten "biomarkers", including lean body mass, cholesterol, aerobic capacity, blood sugar tolerance and muscle strength.

When these biomarkers show the body functioning well it means the body is younger than it might be by the calendar.

Kenton, 60, reckons her biological age is 40-45 and she certainly doesn't look a day over 50.

But when the body isn't functioning as well, the body could be older than it seems and quality of life affected by premature signs of aging.

As soon as Kenton discovered the concept of biological age, she set out to find out how to keep healthy and, therefore, stay young.

As the author of 30 books on health and lifestyle, she is experienced in talking about health but she also wanted hard scientific facts. "This is not a fantasy or a vague idea, this is hard-hitting science."

The biomarkers used to measure biological age were first developed by two scientists at the United States Department of Agriculture and Kenton researched more information on the process of ageing from scientists, doctors and biochemists all over the world.

Kenton found one of the most common causes of faster ageing is Syndrome X, or insulin resistance synd-rome, which slows down the body's ability to burn energy efficiently.

Syndrome X is caused by many of the staples of modern living - a diet high in carbohydrate and sugar, and extreme stress. Kenton claims it affects up to 80 per cent of the population and is ageing us fast.

"Syndrome X carries with it an increased risk of just about every age-related disorder you can name, from eye problems, cancer, exhaustion and anxiety to a poor sense of self worth."

But with knowledge comes power. Kenton has also investigated the ways in which we can fight conditions like Syndrome X and therefore stay young.

Using the latest in anti-aging research and natural remedies, as well as explaining how to eat and exercise, she believes she has exploded the aging myth.

"By making simple changes in the way we eat, use our bodies, handle stress and align ourselves creatively and spiritually, the latest research says we can defy time and stay young."

Kenton even claims it is possible to reverse the process of ageing. "There is scientific proof that changing your lifestyle can rejuvenate the body in medically measurable ways."

Kenton says a lot of it is about confidence, something that can be knocked by getting older and negative attitudes in society to the elderly.

"Take control of your life, your health and your dreams to make you more truly who you are and whoever you want to become."

Age Power by Leslie Kenton (Vermilion, £10.99) is available now at bookshops.

by Louise Gray, features@theargus.co.uk