Background: The relationship between socioeconomic position and obesity has been established, however the extent to which specific behavioural factors mediate this relationship is less clear. This study aimed to ascertain the contribution of leisure-time physical activity (LTPA) and specific dietary elements to social disparities in obesity within the baseline (1990-1994) Melbourne Collaborative Cohort Study (MCCS).
Methods: 18, 489 women and 12, 141 men were included in this cross-sectional analysis. A series of linear regression models were used in accordance with the products of coefficients method to examine the mediating role of LTPA, alcohol, soft drink (regular and diet), snacks (healthy and sweet), savoury items (healthy and unhealthy) and meeting fruit and vegetable guidelines on the relationship between education and Body Mass Index (BMI).
Results: Compared to those of lowest educational attainment, those of the highest educational attainment had a 1kg/m² lower BMI. Among men and women, 27% and 48% of this disparity was attributable to LTPA and diet, respectively. Unhealthy savoury item consumption and LTPA contributed most to the mediated effects in men and women, followed by alcohol and diet soft drink consumption among women.
Conclusions: Diet and LTPA are modifiable behavioural risk factors for the development of obesity which contribute substantially to inequalities in BMI. Our findings add to the body of knowledge around potential behavioural factors which, if effectively targeted by public policy, could reduce social inequalities in obesity.