Background: We have previously demonstrated that between the years 1980 and 2000, the mean body mass index (BMI) of the urban Australian population increased, with greater increases observed with increasing BMI. The current study aimed to quantify trends over time in BMI according to level of education between 1980 and 2007.
Methods: We compared data from the 1980, 1983 and 1989 National Heart Foundation Risk Factor Prevalence Studies, 1995 National Nutrition Survey, 2000 Australian Diabetes, Obesity and Lifestyle Study and the 2007 National Health Survey. For survey comparability, analyses were restricted to urban Australian residents aged 25-64 years. BMI was calculated from measured height and weight. The education variable was dichotomised at completion of secondary school. Four age-standardised BMI indicators were compared over time by sex and education: mean BMI, mean BMI of the top 5% of the BMI distribution, prevalence of obesity (BMI⩾30 kg m(-)(2)), prevalence of class II(+) obesity (BMI⩾35 kg m(-)(2)).
Results: Between 1980 and 2007, the mean BMI among men increased by 2.5 and 1.7 kg m(-)(2) for those with low and high education levels, respectively, corresponding to increases in obesity prevalence of 20 (from 12-32%) and 11 (10-21%) %-points. Among women, mean BMI increased by 2.9 and 2.4 kg m(-)(2) for those with low and high education levels, respectively, corresponding to increases in obesity prevalence of 16 (12-28%) and 12 (7-19%) %-points. The prevalence of class II(+) obesity among men increased by 9 (1-10%) and 4 (1-5%) %-points for those with low and high education levels, and among women increased by 8 (4-12%) and 4 (2-6%) %-points. Absolute and relative differences between education groups generally increased over time.
Conclusions: Educational differences in BMI have persisted among urban Australian adults since 1980 without improvement. Obesity prevention policies will need to be effective in those with greatest socio-economic disadvantage if we are to equitably and effectively address the population burden of obesity and its corollaries.