A randomized controlled trial study using WhatsApp-delivered transtheoretical model–based intervention to promote healthy eating habits and anthropometric measurements for male firefighters

Background: Fruit and vegetables (F&V) consumption is critical to preventing non-communicable diseases such as overweight and obesity. However, many people, including firefighters, focus on physical exercise to strengthen their physical fitness but ignore healthy eating, especially F&V consumption. The aim of this study was to investigate the association between a stage-matched health promotion program delivered through WhatsApp and the stage of change for F&V intake and its influence on anthropometric measurements. Methods: Forty-eight firefighters were randomly assigned to either an intervention (health promotion pamphlet and stage-matched teaching materials through WhatsApp) or active control (health promotion pamphlet) group. Twenty-three were assigned to the intervention group and 25 to the active control group. Results: Significant differences (P < 0.05) were found within the group comparison at the stage of change. More than 60 and 44 percent of firefighters in intervention and active control groups, repectively, were promoted to the “Action” and “Maintenance” stages 6 months after the completion of the intervention. The mixed-effects model results indicated a significant interaction between the two groups across the three time points with regard to the number of fruits consumed (P = 0.0022). This observation suggests that the intervention had a varying effect on the number of fruits ingested over time compared to the control group. Significant differences in body weight, body mass indexes, and waist circumference were observed within both groups (P < 0.05). Conclusions: Stage-matched interventions based on the transtheoretical model delivered through WhatsApp successfully promoted F&V consumption and improved anthropometric measurements among firefighters.