Optimizing dietary adherence in a mobile behavioral weight loss intervention for adults

Obesity remains a critical public health concern. Digital web- and mobile-delivered behavioral weight loss (BWL) interventions with little or no human support are low-cost approaches to adult obesity treatment with 30- 60% of participants achieving 5% weight loss at 6 months. Newer, adaptive intervention approaches have provided alternative treatments to participants who are struggling (non-responders), but few have been tested and have universally used early weight change as an indicator of treatment response. This focus on early weight change obscures the importance of proximal behavioral goals, including the impact of adherence to prescribed dietary recommendations on weight change, and there remains a gap in understanding what types of intervention components can directly target and improve dietary adherence. To fill this gap and inform precision intervention approaches, and in response to NOT-OD-21-100 (NOSI: Improving Patient Adherence to Treatment and Prevention Regimens to Promote Health), we will use an innovative design that uses a factorial trial, as part of the Multiphase Optimization Strategy (MOST) framework, to optimize dietary adherence for non-responders in a mobile BWL intervention. Our team developed a standard mobile-delivered BWL program (core BWL) that is automated except for a brief kick-off session with staff. The core BWL includes daily calorie goals and smartphone-based calorie tracking (dietary self-monitoring; DSM). In our pilot trial, participants identified as non-responders in the first 8 weeks (participants who had 2 consecutive weeks with < 3 days/wk of DSM and calorie goal adherence; 64% of sample) achieved -2.5% (SD=4.8) weight loss at 6 months compared to -11.0% (SD=8.0) among responders. Thus, in the proposed trial we will recruit N=580 adults to participate in the 6-month core BWL program and will use DSM data to continually evaluate and identify participants who are non-responders (< 3 days/wk DSM and calorie goal adherence in prior 2 weeks) over the first 8 weeks. At the time participants are identified as non-responders (~ 65% of sample; N=377), they will be randomized in a factorial trial to receive or not receive each of 4 additional intervention components that specifically target improved dietary adherence: 1) switching to a simple dietary approach, 2) adding autonomous goals + planning modules, 3) adding just-in-time (JIT) messages, and 4) adding 3 coach sessions. Assessments will occur at baseline, 4 weeks (brief), 8 weeks (brief), 3 months, and 6 months to accomplish the following aims: 1) Determine the combination of additional intervention components that maximize dietary adherence among non-responders; 2) Conduct mediation analyses to test the relationships between the additional components and hypothesized mediators (self-regulation, perceived competence, relevance, supportive accountability); and 3) Conduct moderation analyses to identify for whom the additional components are most effective and predictors of early response. Our findings will inform the development of an optimized adaptive intervention that maximizes adherence to prescribed dietary recommendations. Project Number: 1R01HL178992-01 | Fiscal Year: 2025 | NIH Institute/Center: National Heart Lung and Blood Institute (NHLBI) | Principal Investigator: Kimberly Nezami | Institution: UNIV OF NORTH CAROLINA CHAPEL HILL, CHAPEL HILL, NC | Award Amount: $766,277 | Activity Code: R01 | Study Section: Lifestyle Change and Behavioral Health Study Section[LCBH] View on NIH RePORTER: https://reporter.nih.gov/project-details/1R01HL17899201