Welcome to The science behind weight loss, a new Conversation series where we separate the myths about dieting from the realities of exercise and nutrition. In our first instalment, renowned nutritionist Rosemary Stanton explains how diets draw you in, but can’t deliver.
Let’s start with a few facts. Australians' waistbands have increased over the past three decades, with recent data showing 68% of men, 55% of women and 25% of children are overweight or obese.
Excess body fat is a problem for the individual. And it’s ultimately a problem for society because it overloads the national health budget.
Health problems due to excess body fat include an increased risk of type 2 diabetes, coronary heart disease, high blood pressure, asthma, sleep apnoea, musculoskeletal conditions (including osteoarthritis) and certain types of cancer (especially colorectal and breast cancer in post-menopausal women).
There is good evidence to show genes play a role in obesity and explain why some people gain more weight than others when their energy intake exceeds their body’s needs. But genetic factors can’t explain the rapid increase in excess body fat over the past 20 to 30 years.
So what has changed? Two obvious factors stand out.
Physical activity has decreased as we have embraced labour-saving devices and sedentary behaviours. Changes in urban design and the use of cars for transport also play major roles.