Peer-to-Peer Referral Networks and Six-Month Outcomes in a Tirzepatide-Supported Digital Weight-Loss Service: A Retrospective Cohort Study

Real-world effectiveness of tirzepatide-supported obesity treatment depends on sustained adherence and engagement, yet the influence of peer-to-peer referral pathways within digital weight-loss services (DWLSs) is poorly understood. This retrospective cohort study analysed deidentified data from adults initiating tirzepatide through an Australian DWLS (Juniper) between 20 May and 2 December 2025. Patients were classified as peer-referred (via direct referral link) or non-referred (organically acquired). Baseline characteristics, financial markers and early engagement (month-1 weight logging) were compared between groups, and 6-month outcomes included medication adherence (≥5 orders within 183 days), per-protocol persistence (≥1 verified weight entry at days 173–193) and percentage weight loss. Propensity score matching (1:1, nearest neighbour) on age, sex at birth, ethnicity, baseline BMI, comorbidity count, prior GLP-1 RA use and first-order price was used to compare 6-month weight loss between referred and non-referred patients with adequate follow-up and weight data. The cohort comprised 2,576 referred and 31,873 non-referred patients; referred patients were more often male (23.0% vs 7.8%; p < 0.001) and less likely to have prior GLP-1 RA use (17.0% vs 23.0%; p < 0.001), with otherwise similar baseline profiles. Among 17,149 patients with ≥183 days of follow-up, referred patients showed higher 6-month medication adherence (48.0% vs 42.0%; p < 0.01) and per-protocol persistence (35.0% vs 27.0%; p < 0.01). In 1,076 matched pairs, referred patients achieved greater 6-month percentage weight loss (16.16% vs 14.06%; p < 0.001) and higher rates of ≥10% (84.0% vs 66.5%; p < 0.001) and ≥15% (62.0% vs 48.0%; p < 0.001) weight loss. These preliminary findings suggest that peer-to-peer referral pathways may be associated with improved retention and outcomes in unsubsidised, tirzepatide-supported digital obesity care.