Role of program theory in a realist inspired process evaluation of a pilot study investigating Time-Restricted Eating in the Treatment of Type 2 Diabetes – the RESET2 Pilot Study

Introduction: The ability to initiate and maintain health behaviour changes in daily living is important for investigating the effects of such changes and, also, for the potential and relevance of these in practice. In the process of co-designing a 1-year RCT to evaluate clinically relevant effects of a Time-Restricted Eating (TRE) intervention in the treatment of type 2 diabetes (T2D) a needs assessment and a pilot study were conducted. The findings of the needs assessment study combined with knowledge from relevant theories informed development of an Initial Program Theory (INT) suggesting key mechanisms expected to influence initiating TRE, intervention retention rates and degree of adherence to TRE. Based on the initial program theory three intervention core components were formulated which formed basis of the process evaluation of the pilot study. The present study focuses on how the findings of the process evaluation in terms of acceptance of the intervention key components and experiences of the participants on implementing TRE in their daily life resulted in preparation of (Intervention activity)-Context-Mechanism-Outcome ((I)CMO) configurations related to retention and adherence to TRE.
Methods: All participants were interviewed at three timepoints during the intervention (After Visit 1 at baseline, after Visit 2 at 8 weeks and at the end at 12 weeks). The interviews after Visits 1 and 2 were conducted by phone calls and were mainly investigating how participants were experiencing and felt supported the intervention approach and activities. The phone calls were audio-recorded. The interviews at Visit 3 addressed in addition to the above-mentioned topics, how participants experienced implementing TRE in their daily life in terms of coping strategies, barriers and facilitators, motivation, and physical and mental well-being. The interviews were audio-recorded and transcribed verbatim. Analyses were focusing on pre-defined topics and used a deductive qualitative content analysis approach.
Findings: Based on the analyses (I)CMO configurations are presented suggesting how participants’ different contexts influenced retention and adherence (CMOs) and, also how the intervention activities impacted participants differently in terms of feeling supported in maintaining TRE (ICMOs). Several contextual factors such as being supported by relatives, level of social life, having mental and physical challenges, working schedules and family structures influenced participants’ experiences of implementation of TRE.
Discussion: One specific health behaviour change intervention does not fit all, neither in relation to the appeal of the approach per se nor to the circumstances that are influencing individual abilities and capabilities to performing the needed changes. Knowledge of for whom, how and under which circumstances an intervention works enables more tailored interventions, also in terms of how interventions and practice can better support individuals in their change processes. More research is needed on how to operationalise such knowledge in practice.
Dissemination and Impact: The findings have informed the design of a 1-year RCT which will provide knowledge on how the intervention works in the longer term.