Psychosocial Mechanisms of Exercise–Eating Behavior Change Coaction Processes Within Community-Based Obesity-Reduction Programs

Coaction theory suggests improvement in one health behavior carries over to advancements in other health behaviors. There is evidence of increased exercise leading to improved eating; however, data on its psychosocial mechanisms required to adequately inform behavioral weight-management interventions are lacking. Theory suggests that self-regulation, and the relationship of self-regulation to self-efficacy, promote such carry-over processes. Participants in a community-based obesity program who completed no/minimal weekly exercise at baseline were randomized by participating facility using computer-generated random numbers into 6-month treatments emphasizing either weight loss education (n = 39) or self-regulation/self-efficacy (SR/SE) methods (n = 90). Improvements in exercise outputs, exercise- and eating-related self-regulation and self-efficacy, negative mood, dietary behaviors, and weight were significant overall, and significantly greater in the SR/SE group. Carry-over of increased exercise to improved dietary behaviors was suggested. Paths from the treatment group to dietary changes at 6 and 12 months were significantly mediated by associations of changes in (a) exercise-related self-regulation leading to eating-related self-regulation, (b) exercise-related self-efficacy leading to eating-related self-efficacy, and (c) exercise leading to improved mood. Identified relationships between self-regulation and self-efficacy changes were particularly relevant in the dietary-change context. Weight losses over 6, 12, and 24 months, associated with exercise and dietary changes, were 2.2×–2.7× greater in the SR/SE group than in the weight loss education group (−6.0% vs. −2.6%; −5.6% vs. −2.5%; and −5.1% vs. −1.9%, respectively). Advantages of treatment foci on self-regulatory skills and self-efficacy over typical weight loss education were supported. Clarification of psychosocial mechanisms of the increased exercise → improved eating-behavior relationship, including effects of increased exercise on mood, informed continued advancements in theory-driven obesity treatments.