Effectiveness of a Digitally Assisted Obesity Interval Rehabilitation on Physical and Psychological Health-Related Quality of Life – A Quasi- Experimental Study

$\\textbf{Background}$ Obesity presents a significant public health burden in industrialized countries due to its association with reduced life expectancy, work ability, and health-related quality of life (HRQoL). Thus, we examined the effectiveness of a digitally assisted obesity interval rehabilitation compared to conventional obesity rehabilitation with respect to physical and psychological HRQoL. This prospective, non-randomized controlled trial included 412 participants (intervention group: 222; control group: 190) recruited from nine German obesity rehabilitation clinics between 2021 and 2023. The intervention group participated in a digitally assisted obesity interval rehabilitation, while the control group attended conventional obesity rehabilitation without digital assistance. Physical and psychological HRQoL were assessed at baseline, six, and 12 months of follow-up through the 12-item short form survey. We estimated the time×group interaction using multilevel linear mixed effects models, testing random effects (participants and clinics) and fixed effects (age, gender, Body-Mass-Index, and physical activity) through stepwise modeling. Estimated marginal means are presented. $\\textbf{Results}$ No statistically significant time×group interaction was observed, suggesting that the digitally assisted obesity interval rehabilitation did not lead to different physical or psychological HRQoL outcomes compared to conventional obesity rehabilitation (physical HRQoL: β = -0.08, 95% CI [-2.01–1.85], t(726) = -0.08, p = 0.935; psychological HRQoL: β = 0.72, 95% CI [-1.44–2.87], t(729) = 0.65, p = 0.514). However, physical and psychological HRQoL showed small improvements over 12 months (physical HRQoL: β = 3.29, 95% CI [1.92–4.66], t(708) = 4.72, p < 0.001; psychological HRQoL: β = 2.07, 95% CI [0.54–3.60], t(710) = 2.65, p = 0.008) in both groups. Sensitivity analyses confirmed primary analysis and highlighted a potential relevance of BMI change in predicting HRQoL. $\\textbf{Conclusion}$ Digitally assisted obesity interval rehabilitation was not associated with superior physical or psychological HRQoL outcomes compared with conventional obesity rehabilitation. However, both approaches resulted in small improvements in physical and psychological HRQoL over 12 months. Given the similar HRQoL trajectories, digital assistance might be a useful complementary format within obesity rehabilitation in Germany. Further research may benefit from focusing on mitigation of attrition bias, longer follow-up periods and evaluating within-person variations.