Does socioeconomic status moderate the association between theory of planned behaviour variables and health promoting dietary behaviour? A systematic review and meta-analysis.

Dietary behaviours are strongly patterned by socioeconomic status (SES). However, the role of SES in the self-regulation of health promoting dietary behaviour is not fully understood. This systematic review with meta-analysis investigated whether four individual-level measures of SES (income, occupation, education and race) moderate the relationships between Theory of Planned Behaviour (TPB) variables and health promoting dietary behaviour in adults. A systematic literature search identified 65 studies from 51 articles providing information on TPB variables, SES and health promoting dietary behaviour. Random-effects meta-analyses were conducted to generate pooled correlations corrected for sampling and measurement error. Results showed that all TPB variables were significantly associated with health promoting dietary behaviour, with intention having the strongest correlation with behaviour (21% of variance explained), followed by perceived behavioural control (PBC) (11%) attitude (7%) and subjective norm (2%). Random-effects meta-regression was used to investigate the moderating effects of individual-level measures of SES on these correlations. Results showed that none of the SES indicators were significant moderators of the relationship between TPB variables and health promoting dietary behaviour. These results suggest that associations between social-cognitive predictors and healthy dietary behaviour are not patterned by individual-level SES measures.