Background: We have previously shown that between 1980 and 2000, age-adjusted mean body mass index (BMI) of urban Australian adults increased by 1.4kg/m² and 2.1kg/m² for men and women, respectively.¹  The prevalence of obesity doubled to around 20%, while the increasing right skew of the population BMI distribution resulted in a four-fold increase in the prevalence of severe obesity.¹  Obesity prevalence has continued to increase in Australian adults, reaching 28% in 2012. The current study aimed to quantify trends in BMI according to socioeconomic position (SEP) among men and women from 1980 to 2007.
Methods: We compared data from the 1980, 1983 and 1989 National Heart Foundation Risk Factor Prevalence Survey (RFPS), the 1995 National Nutrition Survey (NNS), the 2000 Australian Diabetes, Obesity and Lifestyle Study (AusDiab), and the 2007 National Health Survey (NHS). Analyses were restricted to residents from Australian capital cities aged 25-64. BMI was calculated from measured height and weight and individual level SEP was defined as having completed secondary school or not.
Results: Socioeconomic inequalities were evident across all survey years for each age and sex strata according to mean BMI, prevalence of obesity and mean BMI in the top fifth percentile of BMI distribution. The age standardised prevalence of obesity increased from 12% to 31% and 10% to 21% between 1980 and 2007 for low and high SEP men, respectively. For women, the prevalence of obesity increased from 12% to 28% and 7% to 18% for low and high SEP groups, respectively.
Conclusions: Inequalities in BMI have persisted in the Australian adult population since 1980 with no signs of improvements, and a possible worsening in recent years. It is essential that interventions to address the increasing trend of obesity have the dual goal of improving population levels of weight and reducing its associated disparities.