Generalization of theory-based predictions for improved nutrition to adults with morbid obesity: Implications of initiating exercise

Exercise is a robust predictor of long-term success with weight loss, and research based on social cognitive theory suggests that exercise program-induced changes in self-regulation, mood, and self-efficacy transfer to improved eating. These relationships were tested in adults with morbid obesity (overall M_age = 43 years; 86% female; M_{body mass index} = 45 kg/m²) participating in a 6-month treatment of cognitive-behaviorally supported exercise paired with either standard nutrition education (n = 87) or cognitive-behavioral methods for controlled eating (n = 89). Based on multiple mediation analyses, improvements in self-regulation and self-efficacy were significantly associated with increased fruit and vegetable intake and reduced body mass index (BMI). The cognitive-behavioral nutrition methods were associated with greater improvements in fruit and vegetable intake and BMI, however, within both models, complete mediation was found after simultaneous entry of changes in self-regulation, mood, and self-efficacy, and exercise volume as mediators. Only the indirect effect of change in self-regulation was a significant (or marginally significant) independent mediator. Generalization of previously identified relationships between exercise program-induced improvements in psychosocial variables and improvements in nutrition and BMI were supported for individuals with morbid obesity. Based on these relationships, implications for behavioral treatments were discussed.