International evidence has suggested that waist circumference (WC) is increasing faster than weight. Whether this is the case for Australian adults, and across subgroups of the population, is yet to be quantified.
We selected urban Australian adults aged 25 to 69 years from three nationally representative datasets with measured weight and WC: the 1989 National Heart Foundation Risk Factor Prevalence Study; 2000 Australian Diabetes, Obesity and Lifestyle Study; and 2012 National Nutrition and Physical Activity Survey. Linear regression was used to quantify increases in WC over time that were unaccounted for by increases in weight, stratified by sex and adjusted for age and smoking status. Additionally, analyses stratified by body mass index (BMI) category, age, education and smoking status were performed to test for subgroup differences.
Between 1989 and 2012 weight and WC increased for all population groups. Among women increases in WC and weight were 10.6cm (95% CI 9.6, 11.6) and 5.3kg (4.1, 6.6) respectively. Corresponding increases for men were 7.3cm (6.4, 8.2) and 7.0kg (5.8, 8.2). Increases in WC were significantly greater than expected from increases in weight across all subgroups of sex, BMI, education and smoking status. Among women, WC increased by 6.7cm (6.2, 7.2) over what would be expected from increases in weight. Corresponding values for men were 2.8cm (1.5, 4.1). Increases were greater among normal weight women (6.9cm (6.3, 7.4)) and men (3.7cm (2.9, 4.5)), higher educated women (7.1cm (6.5, 8.4)) and men (3.3cm (2.0, 4.7)), women who were current or former smokers (7.5cm (6.5, 8.4)) and men who were never smokers (3.6cm (1.0, 6.1)).
We provide evidence that in recent decades there have been greater increases in WC than expected from increases in weight, with important subgroup differences. A better understanding of these changes is needed to ensure optimal monitoring and intervention for obesity.