Rationale
There has been no analysis to date
of the behavioural factors associated with differences in weight gain across
socioeconomic strata. Determination of these factors is important for informing public
policy that can reduce socioeconomic inequalities in obesity.
Methodologies
We utilised the 21,479 participants
from the Melbourne Collaborative Cohort Study who attended the baseline
(1990-1994) and follow-up (2003-2007) surveys, were of Australian or Northern
European country of birth and were not missing data on education, anthropometric
or behavioural factors of interest. We further selected the 5,026 men and 8,671 women who
had gained or maintained weight over time (follow up weight ≥ baseline weight).
A series of linear regression models were used in accordance with the products of
coefficients method to analyse the mediating role of leisure time physical
activity, alcohol, soft drink (regular and diet), snacks, savoury items and
fruit and vegetable consumption on the relationship between education and body mass
index (BMI) at follow-up (adjusted for baseline BMI, representing BMI change).
All models were stratified by sex and adjusted for age and smoking status.
Major findings
Total population mean baseline age
was 53, and 43% of these 13,697 persons were of low education.Men showed no significant educational-differences in BMI gain (-0.08 kg/m2
(-0.17, 0.01)). Among women there was significant educational-differences in
BMI gain (-0.10 kg/m2 (-0.18, -0.03)) indicating that independent of
baseline, women of a high education had a 0.10 kg/m2 lower BMI gain
over time. Forty percent of this difference was attributable to two of the
mediating factors analysed, alcohol (29%) and diet soft drink (11%).
Conclusion
These results suggest that diet
soft drink and alcohol are likely to represent drivers of the relationship
between lower education and greater weight gain over time in Australian women. Public
policies which target these behaviours may therefore prevent and reduce obesity
in an equitable manner.