Background: Two in three Australian adults live with overweight or obesity. While modern pharmacotherapy has mitigated the biological barriers to weight loss, long-term success remains challenged by poor adherence, limited accessibility, and persistent behavioural determinants. Digital weight-loss services (DWLS), combining modern pharmacotherapy with asynchronous remote support, are increasingly adopted. Emerging evidence links greater engagement to superior outcomes. This study explores six-month weight loss and the role of digital engagement in a real-world per-protocol DWLS cohort.
Methods: A retrospective per-protocol cohort study was conducted among adults enrolled in a commercial Australian DWLS receiving tirzepatide or semaglutide between 29 May and 29 December 2025. Eligible participants had a BMI ≥25, received at least five medication deliveries, and submitted verified six-month weight data. Six-month percentage weight loss was the primary outcome, with ANOVA assessing group differences and multivariable linear regression exploring predictors. K-means clustering identified digital engagement profiles. Analyses were performed per medication group.
Results: DWLS-supported tirzepatide users lost a mean of 16.58% and semaglutide users 13.68% at six months. Three engagement profiles were identified: low-engagers, self-directed, and actively-engaged, with low-engagers achieving significantly lower weight loss (tirzepatide: 13.6%; semaglutide: 12.1%) than both high-engagement clusters (tirzepatide: 17.4% and 17.4%; semaglutide: 14.4% and 13.3%, p≤0.002). Engagement cluster, BMI, weight loss plateau, and previous GLP-1 use were the strongest predictors. While almost all patients achieved clinically significant weight loss, those with less than 5% loss (n=439) showed higher prior GLP-1 use and lower app engagement, but comparable medication adherence to the full cohort. Within the actively-engaged tirzepatide cluster, chatbot-preferring patients achieved greater weight loss than health coach-preferring patients (19.7% vs. 17.2%, p=0.003).
Conclusion: These findings demonstrate real-world effectiveness of DWLS alongside medication-supported obesity care, achieving clinically significant weight loss in almost all patients and meaningfully greater outcomes in those with high engagement.