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.
- Australian Bureau of Statistics (2011–2012) Australian Health Survey, Nutrition and Physical Activity, 2011–12, Table Builder. Findings based on use of ABS TableBuilder dataGoogle Scholar
- Australian Bureau of Statistics (2014) Australian health survey: nutrition first results - foods and nutrients, 2011–12. Australian Bureau of Statistics, CanberraGoogle Scholar
- Beenackers MA, Kamphuis CB, Giskes K, Brug J, Kunst AE, Burdorf A, van Lenthe FJ (2012) Socioeconomic inequalities in occupational, leisure-time, and transport related physical activity among European adults: a systematic review. Int J Behav Nutr Phys Act 9:116. https://doi.org/10.1186/1479-5868-9-116 CrossRefPubMedPubMedCentralGoogle Scholar
- Cancer Epidemiology Centre (2008) Melbourne collaborative cohort study databook. The Cancer Council Victoria, MelbourneGoogle Scholar
- Forouzanfar MH et al (2016) Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks, 1990–2015: a systematic analysis for the Global Burden of Disease Study 2015. Lancet 388:1659–1724. https://doi.org/10.1016/S0140-6736(16)31679-8 CrossRefGoogle Scholar
- Gearon E, Backholer K, Hodge A, Peeters A (2013) The mediating role of dietary factors and leisure time physical activity on socioeconomic inequalities in body mass index among Australian adults. BMC Public Health 13:1214. https://doi.org/10.1186/1471-2458-13-1214 CrossRefPubMedPubMedCentralGoogle Scholar
- Government Office for Science (2007) Foresight. http://www.bis.gov.uk/assets/foresight/docs/obesity/11.pdf
- Lohman TG, Roche AF, Martorell R (1988) Anthropometric standardization reference manual. Human Kinetics Books, ChampaignGoogle Scholar
- MacInnis RJ, English DR, Hopper JL, Haydon AM, Gertig DM, Giles GG (2004) Body size and composition and colon cancer risk in men. Cancer Epidemiol Biomark Prev 13:553–559Google Scholar
- MacKinnon DP (2008) Introduction to statistical mediation analysis. Multivariate applications. Psychology Press, New YorkGoogle Scholar
- National Health and Medical Research Council (2009) Australian guidelines to reduce health risks from drinking alcohol. Canberra, AustraliaGoogle Scholar
- PwC (2015) Weighing the costs of obesity: a case for action. https://www.pwc.com.au/pdf/weighing-the-cost-of-obesity-final.pdf
- Smith JD, Hou T, Hu FB, Rimm EB, Spiegelman D, Willett WC, Mozaffarian D (2015) A comparison of different methods for evaluating diet, physical activity, and long-term weight gain in 3 prospective cohort studies. J Nutr 145:2527–2534. https://doi.org/10.3945/jn.115.214171 CrossRefPubMedPubMedCentralGoogle Scholar
- Ward H, Tarasuk V, Mendelson R, McKeown-Eyssen G (2007) An exploration of socioeconomic variation in lifestyle factors and adiposity in the Ontario Food Survey through structural equation modeling. Int J Behav Nutr Phys Act 4:8. https://doi.org/10.1186/1479-5868-4-8 CrossRefPubMedPubMedCentralGoogle Scholar
- World Cancer Research Fund/American Institute for Cancer Research (2007) Food, nutrition, physical activity, and the prevention of cancer: a global perspective. American Institute for Cancer Research, Washington DCGoogle Scholar
- World Health Organization (2003) Joint WHO/FAO expert report on diet, nutrition and the prevention of chronic disease. World Health Organization, GenevaGoogle Scholar