Background: Physical activity is a predictor of maintained weight loss; however, causal mechanisms are unclear. Behavioral theories suggest that associated psychologic changes may indirectly affect weight loss.
Objective: We sought to test the association of a behaviorally based exercise support protocol (The Coach Approach [CA]), with and without a group-based nutrition education program (Cultivating Health), with adherence to exercise and changes in physiologic and psychologic factors, and to assess theory-based paths to weight and body-fat changes.
Setting: The study took place in YMCA wellness centers.
Study subjects: Study participation was open to formerly sedentary obese women.
Design: Study participants were randomly assigned to the CA Only (CA; n = 81), The CA Plus Cultivating Health (CA/CH; n = 128), or the control (n = 64) group. We contrasted dropout and attendance rates and changes in self-efficacy (SE), physical self-concept (PSC), total mood disturbance (TMD), body areas satisfaction (BAS), and select physiologic factors during a six-month period. We also analyzed proposed paths to weight loss.
Results: The CA and CA/CH groups had significantly lower exercise dropout rates (χ2 = 44.67, p < 0.001) and higher attendance rates (F = 10.02; p < 0.001) than the control group did. Improvements in body fat, body mass index (BMI), and waist circumference were significant for only the CA and CA/CH groups. Significant improvements in TMD, PSC, and BAS scores were found for all groups, with effect sizes greater in the groups incorporating the CA protocol. Within the five paths assessed, entry of changes in TMD and BAS scores into multiple-regression equations, along with SE and PSC scores, increased the explained variance in exercise session attendance from 5% (p = 0.01) to 16% (p < 0.001). Exercise session attendance was significantly associated with changes in body fat (r = −0.41; p < 0.001) and BMI (r = −0.46; p < 0.001).
Conclusion: Counseling based on social cognitive and self-efficacy theory may increase exercise adherence and improve variables indirectly related to weight and body-fat reductions. Although decreases in body fat and BMI were obtained, they appeared less pronounced than psychologic improvements. Additional research on interrelations of physical activity, psychologic factors, and weight change is warranted for development of obesity treatments.