Relationship of Exercise Program Participation with Weight Loss in Adults with Severe Obesity: Assessing Psychologically Based Mediators

BACKGROUND: Although exercise is related to weight loss, minimal energy expenditures typical in deconditioned persons explain only small portions of this reduction. Thus, it has been suggested that exercise-induced changes in psychological variables associated with appropriate eating may be mediators. METHODS: Adults with obesity (N = 106; Mean BMI = 42.0; SD = 6.0 kg/m), volunteering for a cognitive-behavioral exercise support program and group nutrition information, were assessed on overall mood, self-efficacy for controlled eating, self-regulation skills usage for appropriate eating, recalled volume of physical activity, body mass index (BMI), and waist circumference at baseline and at month six. RESULTS: All within-subject changes were significant (P < 0.001) and as expected, changes in volumes of physical activity were significantly related to BMI (β = -0.52) and waist circumference (β = -0.63) changes. These relationships were partially mediated by changes in self-efficacy and self-regulation scores. Mediation of mood changes did not, however, reach statistical significance. CONCLUSION: In severely obese persons initiating behaviorally supported exercise, weight loss may be better accounted for by changes in psychological predictors of improved eating such as self-efficacy and self-regulation than by direct energy expenditure. Implications for weight loss theory development and clinical applications were discussed.