Impact of Digital Engagement on Weight Loss Outcomes in Obesity Management Among Individuals Using GLP-1 and Dual GLP-1/GIP Receptor Agonist Therapy: Retrospective Cohort Service Evaluation Study

Background: Obesity is a global public health challenge. Pharmacological interventions, such as glucagon-like peptide-1 (GLP-1) receptor agonists (eg, semaglutide) and dual GLP-1/gastric inhibitory polypeptide receptor agonists (eg, tirzepatide), have led to significant weight loss among users. Digital health platforms offering behavioral support may enhance the effectiveness of these medications. Objective: This retrospective service evaluation investigated the impact of engagement with an app-based digital weight loss program on weight loss outcomes among individuals using GLP-1 receptor agonists (semaglutide) and dual GLP-1/gastric inhibitory polypeptide receptor agonists (tirzepatide) in the United Kingdom over 5 months. Methods: Data were collected from the Voy weight loss digital health platform between February 2023 and August 2024. Participants were adults aged 18-75 years with a BMI =30 or =27.5 kg/m2 with the presence of obesity-related comorbidities who initiated a weight management program involving semaglutide or tirzepatide. Engagement was defined based on attendance at coaching sessions, frequency of app use, and regular weight tracking. Participants were categorized as "engaged"or "nonengaged"accordingly. Weight loss outcomes were assessed over a period of up to 5 months. Statistical analyses included chi-square tests, independent t tests, Kaplan-Meier survival analysis, and calculations of Cohen d for effect sizes. Results: A total of 57,975 participants were included in the analysis, with 31,407 (54.2%) classified as engaged and 26,568 (45.8%) as nonengaged. Engaged participants achieved significantly greater weight loss at each time point. At month 3, engaged participants had a mean weight loss of 9% (95% CI 9% to 9.1%) compared with 5.9% (95% CI 5.9% to 6%) in nonengaged participants (P<.001), representing a mean difference of 3.1 percentage points (95% CI 3.1% to 3.1%). A Cohen d effect size of 0.89 indicated a large effect. At month 5, engaged participants had a mean weight loss of 11.53% (95% CI 11.5% to 11.6%) compared with 8% (95% CI 7.9% to 8%) in the nonengaged participants (P<.001). A Cohen d effect size of 0.56 indicated a moderate effect. Participants using tirzepatide achieved more significant weight loss than those using semaglutide at month 5 (13.9%, 95% CI 13.5% to 14.3% vs 9.5%, 95% CI 9.2% to 9.7%; P<.001). The proportion of engaged participants achieving =5%, =10%, and =15% weight loss was significantly higher than the nonengaged group at corresponding time points from months 3 to 5 respectively (P<.001). Conclusions: Engagement with a digital weight management platform significantly enhances weight loss outcomes among individuals using GLP-1 receptor agonists. The combination of pharmacotherapy and digital behavioral support offers a promising strategy to promote the supported self-care journey of individuals seeking clinically effective obesity management interventions.