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Wednesday, 12 September 2012
Page: 10450

Mr MURPHY (Reid) (19:25): A recent report from the Charles Perkins Centre, the University of Sydney's new research hub for the study of obesity, diabetes and cardiovascular disease, warns that more than 60 per cent of Australian adults are overweight or obese. Professor Steve Simpson, an Australian Research Council Laureate Fellow and former Australian Scientist of the Year, who is now the academic director of the Charles Perkins Centre, recently stated that diseases of diet and lifestyle are 'among the greatest threats to health and quality of life' facing humanity.

Body mass index, or BMI, calculated as the ratio of weight to the square of height, is regarded as a reasonable estimate of the proportion of body fat in humans. A BMI of 18.5 to 25 is in the normal range; so a person with a BMI of 25 to 30 is overweight and a person with a BMI greater than 30 is obese.

Among the more severe complications of being overweight or obese is the development of diabetes, the most common form being type 2, which is rapidly increasing in frequency in Australia and around the world. In Australia between 1989-90 and 2007-08, the age-standardised rate of diabetes more than doubled, from 1.5 per cent to 4.1 per cent of all Australians. Ninety-nine per cent of those cases were type 2 diabetes, a disease largely attributable to lifestyle and nutritional factors.

Diabetes mellitus, to give the disease its formal name, is a disorder of the metabolism of carbohydrate and fat that is normally mediated in the body by the hormone insulin. Insulin is central to the control of blood sugar levels in the body and is released by the pancreas following a meal. In healthy people it causes cells in the liver, muscles and fat tissue to take up blood sugar that would otherwise increase to toxic levels. Diabetics lack this essential regulatory mechanism.

There are actually two forms of diabetes, although both have similar medical consequences. Type 1 diabetes is an autoimmune disease that causes the destruction of beta cells that produce insulin in the pancreas, resulting in an absolute insulin deficiency. It occurs more frequently in children and requires the regular injection of insulin to control blood sugar levels. Type 2 diabetes is a multifactorial syndrome that arises from the combined influence of an inherited susceptibility and the influence of environmental factors, the best known being obesity, age and physical inactivity. It results in a diminished response to insulin in cells that normally absorb sugar from the bloodstream. Some patients with type 2 diabetes may eventually need insulin if other medications fail to control blood sugar levels adequately. While the incidence of type 2 diabetes is clearly linked to the increasing incidence of obesity in the population, the concurrent increase in the frequency of type 1 diabetes in children, growing worldwide at the rate of three to five per cent annually, is a mystery, even if the effects are all too apparent.

The sudden growth in the incidence of type 1 diabetes is seriously troubling, because this form of the disease has the potential to disable or kill people much earlier in their lives than type 2 diabetes. Although the possible causes include infections and the so-called hygiene hypothesis, wherein excessive cleanliness causes the immune system to overreact to allergens and destroy the body's own tissue, so far the most likely cause is, as with type 2 diabetes in adults, an increase in the body mass index of children.

Recent studies of the energy consumption of the Hadza, a tribe of Tanzanian hunter-gatherers, demonstrated that the sedentary lifestyle of Westerners is not responsible for the epidemic of obesity. The study found:

In all analyses, daily energy expenditure among the Hadza hunter-gatherers was indistinguishable from that of Westerners.

The actual cause of increasing weight and diabetes in populations around the world is therefore very likely not the lack of exercise or activity, but rather a measurable increase in the intake of food energy, frequently in the form of junk foods. These products are universally and unscrupulously targeted at children and the less well-off.

Just as health authorities now recognise tobacco and alcohol as being serious threats to health, so too are we starting to recognise the damage from eating too much highly processed food that contains high levels of sugar and fat. We all must do even more to educate Australians, particularly children, about the dangers of overeating such food.