1201st Ordinary General Meeting

"Autoimmune diseases: obesity, nutrition, exercise and eating disorders: what shape are Australians in?"

Professor Ian Caterson AM, Boden Professor of Human Nutrition, Sydney Medical School, University of Sydney

Wednesday 4 July 2012 at 6.30 pm

Union, University and Schools Club, 25 Bent Street, Sydney

Meeting report by Donald Hector

At 1201st Ordinary General Meeting of the Society held at the Union University and Schools Club on Wednesday 4 July 2012, Professor Ian Caterson AM talked about the serious obesity epidemic that confronts Australia. This is not confined to Australia – it is a major health problem all developed countries and increasing alarmingly in the developing world, due to the low cost and ready availability of high-energy foods.

Professor Caterson discussed how the epidemiology involved. From the time of World War II when there was worldwide food rationing to the present, where there is generally a surplus of food, average weight has consistently increased. Currently, young adults are gaining, on average, 1 kg per year. The problem is not how much you weigh, rather it is how fat you are. More particularly the problem is how much visceral fat you have (visceral fat sits around the organs inside the abdominal cavity). Unfortunately for many of us "the fatter you are, the younger you die". A good indicator of obesity due to visceral fat is body-mass index (BMI), defined as your mass in kilograms divided by the square of your height in metres. Normal BMI is in the range of 18.5-24.9. A BMI in the range of 25-29.9 is considered to be pre-obese and a BMI of over 30 is considered to be obese. In Australia, 62% of men and about 50% of women have a BMI greater than 25.

Obesity is implicated in a wide range of debilitating disorders: cardiovascular disease, diabetes, sleep apnoea, hypertension, cancer and infertility (the average BMI of women enrolled in fertility programmes is 32. Losing 6 kg in weight increases fertility fifteen-fold).

At a BMI of about 25 (which is about the median in Australia) the biggest health risk is developing diabetes. Professor Caterson gave interesting case of Sumo wrestlers. They eat a high fat diet (in excess of 6,000 calories per day) but they are very strong and very fit. But when they stop fighting, within a year, 35% of them have developed diabetes and many die of heart disease in their 40s. While they are fit all their weight is outside their abdominal cavity but when they stop fighting and lose their fitness, their visceral fat increases rapidly.

Professor Caterson discussed the impact of this major health issue in terms of "disability-adjusted life-years lost". This is an indicator used by the World Health Organisation that combines into a single measure the debilitating effects of serious disease and mortality. The bad news is that if you smoke, are obese, and you are physically inactive you can look forward to losing about 14 years of good-quality life. But the news was not all bad.

In epidemiological terms, for every kilogram you lose, your death rate decreases by 6%. Changing diet can have a big impact. Eating slightly smaller portions, increasing protein, reducing saturated fat intake (replacing it where possible with monounsaturated fats, such as olive oil), increasing dietary fibre, eating fresh fruit and vegetables and getting regular exercise (ideally, one-two hours a day) can have a relatively quick and significant impact on BMI and overall health.

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