Transforming diet in the workplace: effectiveness of a stage of change–based dietary intervention for sedentary office workers in Southern Sri Lanka – a cluster randomised trial

Abstract Background An unhealthy diet is a key risk factor for increasing non-communicable diseases (NCDs) among office workers and causes a significant health and economic burden. Interventions based on the stage of change theory are becoming more effective, and the effectiveness of dietary interventions in office workers remains to be established. The current study assessed the effectiveness of a stage-matched intervention for dietary behaviour change among office workers. Methods A cluster-randomised trial was conducted in the Galle District, Sri Lanka. Intervention clusters received an intervention tailored to participants’ Stage of Change (SOC) at baseline, whereas the control clusters received no intervention. The SOC and dietary intake were assessed at baseline and post-intervention through a staging algorithm and a 24-hour dietary recall, supplemented by a picture guide and computer software. At the end of three months, changes in the stage of change (primary outcome) and in healthy dietary intake (secondary outcome) were compared between the intervention and control groups using univariate and logistic regression analyses, with a p-value cut-off of 0.05. Results A positive change in SOC was observed in both the control ( p = 0.04) and intervention ( p < 0.001) groups. The intervention group showed significant improvements in cereal, fruit, and vegetable intake and a reduction in unhealthy food intake ( p < 0.001). The intervention was a significant predictor of both primary (OR = 12.2, p < 0.001) and secondary (OR = 25.3, p < 0.001) outcomes. Being a clerical worker (OR = 1.7, p = 0.05) and being in action or maintenance stages at baseline (OR = 3.5, p < 0.001) were significant predictors of primary and secondary outcomes, respectively. Conclusions and recommendations The stage-matched dietary intervention was effective in achieving a change in stage of change and towards a healthy diet. We recommend further studies to assess the intervention’s effectiveness in a more pragmatic manner across different settings. Trial registration The trial was registered in the Sri Lanka Clinical Trial Registry (Registration No. SLCTR/2020/025, Date 15/12/2020).