If your waistline is widening, you're not alone.

Sixty-five per cent of men and 45 per cent of women are now overweight or obese, says the Australian Institute of Health and Welfare. That's an increase of around 15 per cent among both sexes since 1980.

Even children are getting fatter, according to the recent NSW Childhood Obesity Summit.

In the 10-year period from 1985 to 1995, the level of combined overweight/obesity in Australian children more than doubled.

Measuring obesity

Health professionals define "overweight" as an excess amount of body weight that includes muscle, bone, fat and water. "Obesity" specifically refers to an excess amount of body fat. Men with more than 25 per cent body fat and women with more than 30 per cent body fat are considered obese.

Measuring the exact amount of a person's body fat isn't straightforward. In recent years, body mass index (BMI) has become the medical standard used as a proxy for a measure of body fat. BMI is calculated by dividing a person's weight in kilos by height in metres squared.

BMI Categories:

• Normal weight = 18.5 - 24.9
• Overweight = 25 - 29.9
• Obesity = BMI of 30 or greater.

For example if you weigh 68kg and are 1.8 metres tall, you calculate BMI: 68 ÷ (1.8 x 1.8) = 20.9, which falls into the normal weight category.

Note: BMI is based on weight and is not a direct measure of fat.

The health risks

If being overweight was solely an appearance issue, health experts may not worry as much. But obesity is associated with numerous health problems, says Professor Ian Caterson, an obesity expert at the Human Nutrition Unit of Sydney University.

"Diabetes, increased levels of lipids (fats) in the blood (associated with heart disease), osteoarthritis and infertility are just some of the physical consequences," he says.

In a study conducted for Australia's Healthy Weight Task Force in 2001 it was found that heart disease is 40 per cent higher in people who are obese, while diabetes is 30 per cent more common.

Arthritis, when compared with people of acceptable weight, is 50 per cent more prevalent in those who are overweight and 70 per cent more prevalent in the obese.

At the 2002 Sydney Eat and Run conference, the head of the World Health Organisation's nutrition and cancer unit, Dr Elio Riboli, noted that excess weight has also been linked to colon, endometrial, oesophagus and renal cancer as well as post-menopausal breast cancer.

"Obesity is set to be the single biggest disease this century," he said.

As if all of this wasn't enough, obesity has been shown to have a negative effect on levels of functioning, mood and self-esteem.

Financially, too, the cost to the community is high. Australia's annual health bill for the treatment of illness associated with overweight and obesity exceeds $800 million, according to the National Health and Medical Research Council.

Changing our lifestyle

"The reasons we're getting fatter are complex," says Dr Colin Kratzing, a member of Australia's Healthy Weight Task Force and a Brisbane GP.

"For starters, we have engineered all the effort out of our lives," he says.

Remote controls for televisions and garage doors, electric can openers, escalators instead of stairs, even shopping on the internet are all modern "advances" that are robbing us of movement.

"We're also very busy doing sedentary things, like watching television or going to the movies, so we don't have time to pursue active hobbies," says Dr Kratzing.

The Australian Bureau of Statistics recently reported that, of a sample of 13,000 Australians over the age of 18, only 55 per cent say they regularly take part in a sport or physical activity.

That's barely one in two Australians and down from the 59 per cent who said they did so in 1999.

At the same time, many of us rely increasingly on takeaway or convenience food.

Says dietitian Dr Rosemary Stanton: "We are eating more snack foods, fast food, takeaway foods and soft drinks.

"Foods children used to eat at parties, they now eat for snacks. Studies show 80 per cent of children take a packaged snack to school every day and this takes the place of fruit."

Dr Stanton says both children and adults are presented with a distorted menu of foods that are available.

The International Journal of Sports Medicine recently estimated that we would need to walk an extra 19km a day to match the activity levels of our ancestors.

Unfortunately this combination of kilojoule-high food and kilojoule-poor activity is fatal for our appearance and health.

Move More
To lose weight, and keep it off, activity is essential. Health professionals are now putting an emphasis into getting more movement into your day from the moment you rise to the time you go to bed. That means parking the car three blocks from where you want to go and walking or taking the stairs. American researchers recently concluded that at least 80 minutes of what they call incidental activity are needed daily to maintain weight.

Says Dr Stanton: "Parents should walk their children to school, where possible, not drive there. And, if we're going down the road to get a newspaper or a carton of milk, why take the car?

"There is an overwhelming need to get on our feet and exercise. Doing something three times a week is ineffective for fat loss. We have to do something every day."

Here are some fat-burning exercises and the kilojoules they burn for a 68kg person.

• A brisk half hour walk, 924kJ
• A leisurely half hour bicycle ride, 504kJ
• A half hour bicycle ride at moderate speed, 820kJ
• A half hour leisurely swim, 588kJ
• A half hour fast swim, 1050kJ
• A slow half hour jog, 1554kJ
• A quick half hour jog, 1932kJ
• A half hour of singles tennis, 820kJ
• Jumping rope for half an hour, 1575kJ

Eating for weight loss

By now you may be thinking it's time to go on a diet.

But a short-term change in your eating habits isn't enough to keep you on the right track for life, say the experts.

For most people the aim of dieting is to lose as much weight as possible in the shortest amount of time. This means making major changes to what you eat for a set time, then returning to your old eating habits and regaining the lost weight.

Dr Stanton says we need to look very carefully at our food supply and the types of food we are eating.

"What people don't realise, for example, is that a hamburger that contained between 14 and 17 grams of fat in the 1970s now has more than twice the fat.

"We're offered extra cheese on pizzas and meal deals that include enough kilojoules for two days.

"What we need to do is save these foods for special occasions and look really closely at what we eat and drink on a daily basis."

Fruit, vegetables, lean protein, wholegrain cereals and plenty of water are the key to long-term health and longevity, she says. And we should be grilling, steaming or boiling food, not frying.

"Our thirsts should also be quenched with water, not soft drinks or alcohol," says Dr Stanton.

Low Glycemic Index (Gl) foods, like wholegrain breads, fettucini, apples and peaches, may help increase satiety and decrease total food intake, advises Dr Garry Egger, Adjunct Professor of Health Sciences at Deakin University, Melbourne. GI is a measure of the rate of conversion of food to sugar in the bloodstream.

The longer it takes the carbohydrates to be digested, the less the impact on blood sugar and insulin and the healthier the food.

The GI concept implies that a primary cause of heart disease, Type 2 diabetes and obesity is the long-term damage caused by the repeated surges of insulin that come from eating starches and refined carbohydrates.

For constant energy and controlled appetite, the aim is to eat foods that are converted to sugar slowly. Beans, peas and lentils are also low GI foods that bring plenty of protein and other nutrients into the body, but are only about four per cent fat.

American researchers also estimate that someone who doubles their daily fibre intake from 12 grams to 24 grams will absorb around 350 fewer kilojoules a day or 127,750 fewer a year.

Eat wholegrain not white breads, snack on rye crackers, and double your vegetable intake. These foods top the fibre tables: apples, pears, prunes, strawberries, All Bran, oatmeal, wholewheat bread, brown rice, baked beans, chickpeas, kidney beans, peas, tofu, broccoli, carrots, green beans, sweet potatoes, spinach, yams. Include them high on your list of food choices.

Healthy weight control

Fad diets, unbalanced diets, diet pills, diet supplements and other short-term weight loss methods are not recommended for permanent weight control.

The best way to lose excess fat and to maintain a healthy weight in the long-term is to follow a balanced, kilojoule-controlled diet (that improves your eating habits) and to take regular, aerobic exercise.

10 ways to lose fat

• Bulk up sandwiches with raw vegetables such as grated carrot, lettuce and cucumber, not high-fat cheese or processed meats.
• Walk briskly for 15 to 30 minutes every morning, before breakfast. There is some evidence that exercising on an empty stomach may help deplete fat stores.
• To cut down on alcohol intake, substitute one glass of water for every second glass of alcohol you would normally drink.
• Switch to a non-stick frying pan so you don't have to add butter or oil for cooking.
• Instead of sour-cream or cream in savoury dishes, try substituting plain, low-fat yoghurt.
• Stop cooking desserts and try a piece of fresh fruit at the end of a meal instead.
• Avoid buying foods that are comprised mostly of pastry - pies, sausage rolls, Danish desserts.
• If you have a choice between wholegrain products and refined, go for the wholegrain. Experts say they will help you feel fuller, for longer.
• Talk positively to yourself about your body image and your goals. Believe that it is possible for you to lose weight and become a healthier, happier person.
• Enlist support in your efforts to shed kilograms, from your family and friends as well as from your GP. You will reach your goal sooner with support and professional help.