Effect of adherence to self-monitoring of diet and physical activity on weight loss in a technology-supported behavioral intervention

BACKGROUND: Examination of mediating behavioral factors could explain how an intervention works and thus provide guidance to optimize behavioral weight-loss programs. This study examined the mediating role of adherence to self-monitoring of diet and physical activity on weight loss in a behavioral weight-loss trial testing the use of personal digital assistants (PDA) for self-monitoring. METHODS: Mediation analysis was conducted to examine the possible mediating role of adherence to self-monitoring of diet and physical activity between treatments using varying self-monitoring methods (paper record, PDA, and PDA with daily tailored feedback messages) and weight loss. FINDINGS: The sample (N = 210) was predominantly white (78%) and female (85%). Compared to a paper record, using a PDA for self-monitoring diet (P = 0.027) and physical activity (P = 0.014) had significant direct effects on weight loss at 12 months, as well as a significant indirect effect on outcomes through improved adherence to self-monitoring (P(S) < 0.001). Receiving an automated daily feedback message via PDA only had a significant indirect effect on weight through self-monitoring adherence to diet (P = 0.004) and physical activity (P = 0.002). CONCLUSIONS: Adherence to self-monitoring of diet and physical activity is important as the underlying mechanism in this technology-supported behavioral weight-loss intervention.