Relationship of physical activity and weight loss in women with Class II and Class III obesity: Mediation of exercise-induced changes in tension and depression

Exercise is a predictor of both weight loss and mood improvement. Because of the minimal energy expenditure associated with exercise in obese persons due to their poor cardiovascular fitness, it has been suggested that exercise-induced mood change may mediate the relationship of exercise with weight loss for them. In the current experimental study, women with Class II and III obesity (N = 75) participated in a 24-week moderate exercise and nutrition education program at southeastern U.S. Young Men’s Christian Association (YMCA) centers. As expected, exercise session attendance was significantly associated with weight loss (â=-.47), but directly accounted for only an estimated 17% of the loss in weight. Using the Baron and Kenny approach, significant partial mediation was found for changes over 24 weeks in both tension and depression scores. This suggested that exercise indirectly affected weight change through psychological pathways, and supported tenets of social cognitive theory. After replications and extensions, findings may help to improve explanatory theory and weight management treatments.