Diet and physical activity as possible mediators of the association between educational attainment and body mass index gain among Australian adults
To quantify the mediating role of leisure time physical activity (LTPA) and five dietary behaviours on educational differences in 13-year body mass index (BMI) gain across adulthood.
Participants from the Melbourne Collaborative Cohort Study (4791 women; 3103 men) who maintained or gained BMI over 1990–1994 to 2003–2007 and met our inclusion criteria were selected. Education, potential mediators and confounders (age, alcohol, and smoking) were measured at baseline. We conducted sex-specific multiple mediation analyses using MacKinnon’s product of coefficients method.
A higher educational attainment was associated with a 0.27 kg m−2 (95% CI 0.14, 0.39) lesser 13-year BMI gain among women only. We observed significant indirect effects of educational attainment on 13-year BMI gain through LTPA and nutrient-rich foods (each associated with a higher educational attainment and lesser 13-year BMI gain) and diet soft drink (associated with a lower educational attainment and greater 13-year BMI gain), which mediated 10, 15 and 20% of this relationship, respectively (45% in total).
Nutrient-rich foods, LTPA and diet soft drink may represent effective public health targets to reduce inequities in excess weight across adulthood.
KeywordsMediation analysis Socioeconomic factors Diet, food, and nutrition Physical activity Obesity Longitudinal studies
This work was supported by an Australian Research Council (ARC) Linkage grant (LP120100418) and in part by the Victorian Government’s Operational Infrastructure Support (OIS) Program. EG was supported by an Australian Government Research Training Program (RTP) Scholarship, AP was supported by a National Health and Medical Research Council Career Development Fellowship (1045456) and is a researcher within the NHMRC Centre for Research Excellence in Obesity Policy and Food Systems (APP1041020) and Deakin University, WLN is supported by a Monash Graduate Scholarship, a Monash International Post-graduate Research Scholarship and a Baker Bright Sparks Top-Up Scholarship, and KB was supported by a National Heart Foundation of Australia Post-Doctoral Fellowship (PH 12M6824). The MCCS study was made possible by the contribution of many people, including the original investigators and the diligent team who recruited the participants and completed follow-up. We would like to express our gratitude to the many thousands of Melbourne residents who continue to participate in the study. MCCS Data used in this research were obtained from Cancer Council Victoria. MCCS cohort recruitment was funded by VicHealth and Cancer Council Victoria. The MCCS was further supported by Australian NHMRC grants 209057 and 396414 and by infrastructure provided by Cancer Council Victoria. These funding sources had no input into study design, or collection, analysis and interpretation of the data.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Informed consent was obtained from all individual participants included in the study.
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