The western world faces a very significant obesity epidemic. In Australia, two-thirds of our population or 12.5 million are either overweight or obese and as a consequence may experience many medical sequelae including development of the metabolic syndrome, type 2 diabetes, cardiovascular disease, cerebrovascular disease, osteoarthritis and depression, contributing significantly to our health burden. In the first part of this series, we were joined by Joseph Proietto, Professor Emeritus at the University of Melbourne, the Department of Medicine at Austin Health and an endocrinologist specialising in diabetes and obesity to discuss why we become obese. Professor Proietto joins us again to guide us through a strategy of how to treat and manage obesity and direct our patients toward a healthy body mass index (BMI).

Up to two thirds of Australians are either overweight or obese as defined by body mass index (overweight: BMI 25-29.9, obese: BMI >30) with subsequent significant medical consequences including cardiovascular disease, type 2 diabetes, cerebrovascular disease (metabolic syndrome), osteoarthritis and depression. Becoming overweight and obese involves complex interactions between neurohormonal systems of the gut, neurobiology of the brain (particularly the hypothalamus) and leptin production from adipose sites coupled with an environment where there is an abundance of high glycaemic energy dense foods. Science demonstrates that the overarching controls of obesity are genetic (70%) rather than environmental (30%). Adoption studies relating to monozygotic twins demonstrate this. In view of the metabolic consequences of obesity, understanding why we get fat is extremely important to medical practitioners.