Processes of behavior change and weight loss in a theory-based weight loss intervention program: a test of the process model for lifestyle behavior change (International Journal of Behavioral Nutrition and Physical Activity)

Background: Process evaluation is important for improving theories of behavior change and behavioral intervention methods. The present study reports on the process outcomes of a pilot test of the theoretical model (the Process Model for Lifestyle Behavior Change; PMLBC) underpinning an evidence-informed, theory-driven, group-based intervention designed to promote healthy eating and physical activity for people with high cardiovascular risk. Methods: 108 people at high risk of diabetes or heart disease were randomized to a group-based weight management intervention targeting diet and physical activity, or to usual care. The intervention comprised nine group based sessions designed to promote motivation, social support, self-regulation and understanding of the behavior change process. Weight loss, diet, physical activity and theoretically defined mediators of change were measured pre-intervention, and after four and 12?months. Results: The intervention resulted in significant improvements in fiber intake (M between-group difference?=?5.7?g/day, p?