Empowering weight loss: a pragmatic randomized controlled trial of a theory-driven self-regulation mobile app for young adults with excess body weight

Abstract Background/Introduction Obesity is projected to affect more than half of the global population by 2035, posing significant health and economic challenges. While lifestyle modification is considered a cornerstone of weight management, its effectiveness often relies on substantial support systems. Purpose This study aimed to evaluate the effectiveness of a 12-week, standalone Temporal Self-Regulation Theory (TST)-based weight loss mobile application, which integrates self-regulation techniques, food logging, and dietary nudging, in promoting weight loss among young adults with excess body weight. Methods A two-arm, parallel-group, 1:1 randomized controlled trial was conducted, adhering to the CONSORT-Outcomes 2022 Extension guidelines. Participants completed a face-to-face body composition analysis and online questionnaires addressing sociodemographic, self-regulation of eating behaviour, overeating habits, time perspective, eating phenotype, nutrition knowledge, and psychological flexibility. The intervention group used the Eating Trigger Response Inhibition Program 2.0 (eTRIP 2.0), a 12-week app-based program, while the control group received no active intervention. Both groups attended follow-up measurements at weeks 12 and 24. Results A total of 165 participants were enrolled between November 14, 2023, and March 27, 2024. At weeks 0, 12, and 24, the mean weight difference between the intervention and control groups were 0.29 kg (95% CI -3.69 to 4.28 kg), -1.76 kg (95% CI -5.96 to 2.43 kg), and -1.60 kg (95% CI -5.92 to 2.65 kg) respectively. While a significantly higher improvement in weight (-0.89 kg, 95% CI -1.51 kg to -0.27 kg, p=0.005), BMI (-0.32 kg/m2, 95% CI -0.55 kg/m2 to -0.10 kg/m2, p=0.005), waist circumference (-1.50cm, 95% CI -2.80 cm to -0.19cm, p=0.03), waist-hip ratio (-0.01, 95% CI -0.011 to <0.001, p=0.04) and body roundness index (BRI) (-0.18, 95% CI -0.34 to -0.02, p=0.02) were observed in the intervention compared to control group at week 12, no significant differences were found once the app access was ceased at week 12. Psychological outcomes, including intention for weight management, did not differ significantly between groups. However, self-regulation (B=3.08, t=3.95, p=0.005) and overeating habit (B=6.11, t=2.84, p<0.001) were identified as significant predictors of weight change at week 24, together explaining 10.7% of the variance in body weight. This explainability increased to 31.6% when age and sex were accounted for. Notably, a higher proportion of participants across both groups expressed a preference for physical activity over diet as their primary weight-loss strategy. Conclusion(s) This study provides evidence supporting the potential benefits of a TST-based app for improving anthropometric outcomes and psychological constructs. The findings suggest that this intervention holds promise for scalability in both population-based and primary health care settings.