Weight-Loss Treatment-induced Physical Activity Associated with Improved Nutrition through Changes in Social Cognitive Theory Variables in Women with Obesity

Behavioral weight-loss treatments have typically been unsuccessful and a theoretical. Even when treatments were scientifically derived, theory has rarely been used to decompose, and understand the bases of, their effects. This 2-year study evaluated mediation of the prediction of nutritional changes by changes in physical activity, through social cognitive theory variables. Data from women with Class 1–2 obesity, classified as “insufficiently active” (N = 50; Mage = 47.6 years), were extracted from 2 initial trials of a new cognitive-behavioral intervention. That treatment sought to improve self-regulation, mood, and self-efficacy through increased physical activity, to then induce improved eating and long-term weight loss. Data showed significant improvements in self-regulation for controlled eating, mood, self-efficacy for eating, physical activity/exercise outputs, and intake of fruits/vegetables and sweets. In the prediction of changes in fruit/vegetable intake over 6, 12, and 24 months by physical activity changes, changes in the 3 psychosocial variables were significant mediators. For each of those significant overall models (R2-values =.31, .30, and .25, respectively), self-regulation and self-efficacy change were independent mediators. When change in sweets was substituted for fruits/vegetable intake in otherwise identical models, although overall significance was not found, change in mood was a significant mediator. Changes in intake of fruits/vegetables and sweets significantly predicted a 2-year mean weight loss of 5.4 kg (-5.7% reduction). Results generally supported the basis for the architecture of the new cognitive-behavioral treatment. Based on findings, much of the effect of physical activity/exercise on weight loss could be explained through its impact on psychosocial correlates of healthier eating