Results of a pilot sequential multiple assignment randomized trial using counseling to augment a digital weight loss program

Objective: Adaptive interventions may improve the potency and scalability of behavioral weight loss interventions, but the treatments-or treatment combinations-that should be offered are unknown. A two-stage pilot sequential multiple assignment randomized trial was used to test the timing and dose of human support added to a core digital weight loss program. Methods: In stage 1, 99 adults with overweight/obesity were randomized at baseline to a kick-off with or without additional human support. In stage 2, "early non-responders" who had not achieved a 2% weight loss were re-randomized after 4&nbsp;weeks to either biweekly counseling (120&nbsp;min over 8&nbsp;weeks) or a one-time check-in (30&nbsp;min) with a dietitian. "Early responders" continued with the mHealth program alone. Feasibility and acceptability were assessed against pre-specified criteria. Preliminary outcomes (weight loss, self-monitoring and behavioral goal adherence) were explored. Results: The study met&nbsp;all feasibility and acceptability criteria. The rate of early response was 52.5%. Mean (SE) 3-month percent weight losses were significantly greater in early responders (-6.63% (0.72)) than non-responders (-1.70% (0.43), <em>p</em>&nbsp;&lt;&nbsp;0.001). Outcomes were similar by first- and second-line treatment though more counseling (27.3%) than check-in (12.5%) participants achieved a 5% weight loss. Conclusions: Identifying early responders may help optimize weight loss interventions, but more research is needed on rescue treatments for early non-responders. Trial Registration: ClinicalTrial.gov, NCT05929469.