Results of standard weight-loss treatments have been disappointing . Although regular exercise and appropriate eating will manage weight, individuals are not typically able to successfully negotiate common barriers such as time pressures, discomfort, and social pressures, over time, and typically regain any weight lost in short order . This pattern is so typical that treatments are usually evaluated by percentage of weight regained, rather that if weight loss is maintained . Because of poor prospects with such approaches, surgeries such as gastrointestinal bypass, vertical banded gastroplasty, and laparoscopic gastric banding are increasingly the weight-loss treatments of choice for those with class 3 obesity (body mass index [BMI] ≥ 40.0 kg/m2) and class 2 obesity (BMI 35.0-39.9 kg/m2) with one or more comorbidities . Although behavioral weight loss treatments have often been atheoretical, and dependent largely on persons responding to information on appropriate eating and exercise (where there is little evidence of success), accepted behavioral theories have sometimes been used as a basis for intervention strategies .
Self-efficacy theory, for example, posits that people's judgments of their capabilities to carry out actions will predict their behaviors, and suggests that self-efficacy may be increased through attainment of prior success, imitating others' performance, verbal and social persuasion, and perceptions that positive psychological states may be achieved . Researchers posit that self-efficacy is a precondition of behavior change . Although increases in self-efficacy have been attempted through such general methods as encouragement and observation of the success of others, it is possible that purposefully fostering self-regulatory skills use (eg, cognitive restructuring, stimulus control) early in a treatment will induce increased self-efficacy over time. It has been suggested that "behavioral self-regulation" [, p 545] and "coping responses" [, p 38] will lead to self-efficacy and improved outcomes because of their direct connection with overcoming barriers and establishing feelings of competence and success. Because low mood has been shown to be associated with reduced use of self-regulatory skills and perceptions of self-efficacy , and positive changes in mood may promote a "healthier psychological climate" that enhances confidence in pursuing weight management behaviors [, p 320], the established effects of exercise program participation on improved mood  may mediate (significantly reduce or cancel out the relationship between two variables by its entry) this relationship. It has been suggested that treatments should first be based on accepted theory, and then their effects decomposed to determine if changes in variables consistent with the theory predicted outcomes as expected . Such a thorough analytic approach has often been lacking in weight-loss research.
Thus, the present investigation aimed to test a treatment of exercise and nutritional support, based on tenets of self-efficacy theory, which emphasized self-regulatory skills. It was thought that the treatment would be associated with significant increases in measures of self-regulatory skills usage, self-efficacy, and mood. More specifically, changes in self-regulatory skills were expected to be associated with changes in self-efficacy for both physical activity and appropriate eating, but be significantly mediated by mood changes. Additionally, a significant portion of the variance in BMI change was expected to be accounted for by changes in self-efficacy for physical activity and appropriate eating.
Formerly sedentary adults with class 2 and 3 obesity were selected for participation because of the considerable need for a better understanding of theory-based psychological predictors of weight loss in these highly at-risk subgroups. It was hoped that increased knowledge of the effect of self-regulatory skills usage on self-efficacy would yield important data for weight management theory and application.