Motivational and psychosocial outcomes have not been reported in behavioral weight loss programs utilizing the SenseWear Pro armband (SWA) and motivational interviewing; making it difficult to identify motivational components that may be related to weight loss. The Transtheoretical Model (TTM) is one model used to help explain motivation and behavior change through the constructs of decisional balance (DB), diet and physical activity self-efficacy (SE), and cognitive and behavioral processes of change (C-POC, B-POC). The purpose of this study was to assess the changes in TTM constructs of DB, SE, and both C-POC and B-POC in a randomized trial evaluating three different weight loss interventions in obese adults.

Seventy-eight subjects (32 males and 46 females) completed one of three 8-week weight loss interventions with guidance from a health coach and the utilization of motivational interviewing techniques. Group 1 (n = 26) received a behaviorally guided weight loss program (GWLP), Group 2 (n = 26) received a self-monitoring tool called the SenseWear Pro Armband (SWA) with Weight management system (WMS) and Group 3 (n = 26) received both programming options (GWLP + SWA). Weight change and changes in TTM constructs of SE, DB (pros vs. cons), and C-POC and B-POC were assessed at baseline and at the completion of the intervention. Changes in variables across time and condition were assessed using multivariate ANOVAs and the magnitude of effects were reported using effect sizes.

All interventions produced significant weight loss, with no significant differences between groups. Significant changes in TTM constructs were observed over time and some differences were evident between groups. Large effect sizes were found for improvements in SE in groups that received the GWLP (Groups 1 and 3), while slight improvements were seen in the SWA group (Group 2). Decisional balance improved significantly (p < 0.05) in the combined GWLP + SWA intervention (Group 3). Significant improvements (p < 0.001) over time were evident for specific B-POC: counterconditioning, interpersonal systems control, reinforcement management, self-liberation, and stimulus control.

The results of this study support previous evidence showing improvements in self-efficacy directly after an active intervention, but warrants further examination for identifying which processes of change are influenced via self-monitoring techniques and the use of motivational interviewing techniques on motivational and behavioral outcomes. Longer-term studies are needed to determine if these factors may influence maintenance of weight loss.