Walking briskly for 30 minutes every day (which equates to about two miles) is considered the minimum required to maintain a healthy weight. According to research due to be published by Loughborough University, it doesn't matter how that time is made up. "Walking for three minutes 10 times a day appears to have exactly the same effect as doing it in one stretch, " says exercise physiologist Dr David Stensel. His study measured levels of fat in the bloodstream and found that those people who had walked for a minimum of 30 minutes the previous day had lower levels of blood fat than those who had not. "The muscles store fat to use as energy during exercise and take in more fat whenever these stores are depleted. When that doesn't happen, the fat gets stored in adipose tissues and the weight piles on, " he says.

The 30 minutes' walking should be on top of normal activity. For an office worker, this is 5,000 to 7,000 steps a day. A better target might be the 10,000 steps a day first promoted at Queensland University, Australia, where the whole population of the small town of Rockhampton was encouraged to reach the target, using a pedometer. The gadget became an overnight sensation, "a massive health promotion tool" . . . and a favourite topic of end-of-the-day conversation, first in Rockhampton and now throughout the world.

DON'T DIET

Panicking about weight is a leading cause of crash dieting involving rapid weight-loss . . .

which almost inevitably leads to subsequent weight-gain. Weight cycling occurs partly because you lose more lean tissue with rapid weight-loss, which is difficult to maintain, and partly because dieting sets up an unrealistic relationship with food that is forbidden . . . so that you eventually crack and end up putting it all back on again. Almost all dieters regain the weight they lose within two years. Many end up heavier than before.

Calorie-restricted diets will make you feel deprived and hungry . . . and hunger pangs will increase the temptation to binge on sugary and other refined foods.

Even so, obesity is bad for your health. But anyone who's serious about losing weight should take things slowly. If you have a body mass index (weight in kilograms, divided by height in metres squared) of above 25, you will probably need help to lose weight . . . ideally around two pounds (1kg) per week . . . and should seek your GP's help or join a reputable slimming club, says the nutrition scientist Anna Denny.

The idea is to find a diet and lifestyle that you can comfortably live with, rather than to attempt to lose weight periodically with regimes that are hard to maintain. Staying a healthy weight, Denny says, means avoiding fatty meat, fried food and too many biscuits, cakes and pastries; choosing low-fat dairy products; drinking plenty of water;

increasing your intake of fruit and vegetables; and eating plenty of wholegrain bread and cereals.

"A healthy, balanced diet along with a combination of low-impact aerobic exercise (walking, swimming, jogging, dancing) and resistance exercise (weights, Pilates, yoga) that builds and tones muscle is the best way to feel fit and look good."

WATCH YOUR DOSHAS

In Ayurvedic medicine, obesity is blamed on a 'low digestive fire' . . . an imbalance of the Kapha dosha (one of the biological energies in Ayurvedic medicine that combine to determine individual constitution). Adipose tissue, which accumulates on the central abdomen, hips and thighs, makes the digestive fire more sluggish and the fat more difficult to shift. Guggul Plus (available in health food stores), a herbal cocktail that has been used in Ayurvedic medicine for more than 2,000 years, is believed to remove excess fat and stimulate digestion and bowel movements.

You should avoid dairy, wheat, sugar and cold foods, and have a fresh ginger root with a drop of lemon juice before each meal to remove excess fluids from the body. Combine light, warm foods such as soups and basmati rice with heavy, filling ones like carbohydrates, wholegrain cereals and lentils.

THINK YOURSELF THIN

Obsessing about being overweight can be a fruitless and even dangerous activity. At worst, you risk developing an eating disorder such as anorexia, bulimia or binge-eating.

Doing the opposite, however, appears to be extremely healthy. Obsessing about being thin . . . or, rather, using visualisation techniques to persuade yourself that you are thin . . . gives your body the message that being thin is a good thing. "Very soon fattening foods lose their appeal and you become more active and are transformed into a thinner version of the former you, " explains Debbie Johnson, author of Think Yourself Thin (Athena). It's also the logic behind the widespread success of hypnosis in helping people to shed weight and then keep it off. Paul McKenna's video Easy Weight- Loss (Gut Records) encourages people to imagine themselves being slim.

EAT LITTLE AND OFTEN

What we recognise as hunger is often simply our bodies alerting us to the fact that it's our normal feeding time. "Dietary habits are easy to form, especially a large meal which stretches the stomach and creates a rhythm that your body gets used to very quickly, " says Dr Ann Walker, senior lecturer in human nutrition at the University of Reading in the UK. "Instead, eat smaller amounts more frequently, perhaps four meals a day.

It then becomes easier to recognise when you really are hungry."

Having regular snacks of fruit, nuts or seeds will give you slow-release energy throughout the day and serve to avoid the peaks and slumps in your blood sugar levels that can cause cravings for sugary foods.

GIVE UP MEAT

Diets low in carbohydrates and high in protein, such as the Atkins diet, do not keep weight down, according to Cancer Research UK. Last week, the charity announced that the biggest study of nutrition had shown that people on high-carbohydrate, low-protein diets put on the least weight . . . with a healthy weight easier to maintain on a vegetarian diet. "Vegetarians are less likely to put on weight than carnivores, with vegans putting on the least weight, " explains Professor Tim Key, deputy director of Cancer Research UK's epidemiology unit at Oxford University.

SLEEP

ON Our 21st-century lifestyle means that we get two to three hours' less sleep today than people used to 50 years ago . . . and this may at least partly explain the near doubling in the incidence of obesity during this period, scientists believe. Studies show that sleep deprivation boosts our levels of ghrelin, a hormone that makes us feel hungry, while suppressing another, leptin, that makes us feel full. "Evidence is emerging that the abnormalities in these hormones result in an increased desire for high-calorie food, " says Dr Shahrad Taheri, endocrinologist and a leading researcher in the area.

The body, it seems, is upset by this hormonal disturbance, which sends a signal to the brain that more food is needed when, in fact, enough has been eaten, according to Dr Eve Van Cauter, a sleep researcher at the University of Chicago.

Further research has shown that sleeping for four hours or less slows down the fall in another hormone, cortisol, which makes you feel hungry in the evening instead of sleepy. Cortisol normally peaks between about 10am to noon and then falls gradually until it reaches its lowest level at the time you go to bed. But experiments at the University of Chicago have shown that sleep deprivation causes a rise in cortisol levels. Dr Van Cauter subjected fit young men to six days of sleep restriction (allowing them just four hours of sleep a night) and found that the normal fall in cortisol was six times slower than normal, leading to elevated levels of the hormone in the evening.