Does physician familiarity enhance video-based lifestyle counseling in adults with overweight or obesity? A randomized controlled trial.

Abstract

To examine whether physician familiarity, as a proxy for relational continuity, enhances the effectiveness of video-based lifestyle counseling in adults with overweight or class I obesity. A multicenter randomized controlled trial was conducted in six primary care centers in Valencia, Spain, between February and May 2025. A total of 115 participants were randomized (1:1) to receive identical video-based lifestyle counseling delivered either by their own primary care physician (experimental group) or by an unfamiliar physician matched by sex and therapeutic alliance score (control group). The primary outcome was body mass index. Secondary outcomes included blood pressure, glycemic and lipid profiles, Mediterranean diet adherence, physical activity, and health-related quality of life. Mixed-design ANCOVA models adjusted for baseline values were used. Compared with the control group, the experimental group showed lower post-intervention body mass index, with an adjusted between-group difference of -0.5 kg/m² (95% CI: -0.9 to -0.1; P = 0.013; ηₚ² = 0.054), and lower weekly sitting time, with an adjusted between-group difference of -39 min/week (95% CI: -77 to -0.2; P = 0.049). In the per-protocol analysis, the adjusted between-group difference in body mass index was -0.9 kg/m² (95% CI: -1.6 to -0.2; P = 0.009; ηₚ² = 0.104). Within-group improvements in Mediterranean diet adherence and health-related quality of life were observed in the experimental group. Post-intervention knowledge scores did not differ between groups. Video-based lifestyle counseling delivered by patients' own primary care physicians was associated with greater reductions in body mass index and sedentary time than identical content delivered by unfamiliar physicians. These findings suggest that physician familiarity may contribute to the effectiveness of digital lifestyle counseling, although the relational mechanisms underlying this effect require direct evaluation in future studies. Preserving relational continuity in digital patient education interventions by incorporating patients' usual clinicians may improve engagement and effectiveness while maintaining scalability in primary care, particularly for obesity management.