Social Cognitive Mediators of Change in a Group Randomized Nutrition and Physical Activity Intervention Social Support, Self-efficacy, Outcome Expectations and Self-regulation in the Guide-to-Health Trial

In an evaluation of the theoretical foundations of behavior change, the current study examined whether social cognitive (SCT) variables mediated treatment effects on physical activity and nutrition in the recently reported Guide-to-Health trial (GTH). Adults (N = 661) were assessed at baseline, seven months and 16 months to examine whether treatment-related changes in SCT variables at seven months mediated change in nutrition and physical activity at 16 months. GTH treatment effects were mediated by self-efficacy, self-regulation and social support; self-regulation mediated self-efficacy. Social-cognitive variables explained only part of the treatment effects suggesting future investigations evaluate the environmental-selection and affective processes of behavior change.