Using self-efficacy and a transtheoretical model to develop a physical activity intervention for obese women

Purpose. To assess the effectiveness of applying behavior change theory to a physical activity intervention for obese, sedentary women. Design. A 48-week randomized controlled trial. Subjects were randomized to one of two intervention groups. Setting. A university classroom and a local health club. Subjects. Fifty-eight sedentary, obese women. Interventions. A 24-week theory-based physical activity program that aims to change the way subjects think and behave in relation to physical activity (treatment group, n = 29) and a traditionally structured exercise program (control group, n = 29). Measures. Questionnaires on physical activity, stage of change, processes of change, and self-efficacy were completed at baseline, 24 weeks, and 48 weeks. Results. Twenty-seven of the 29 participants in the treatment group and 17 participants in the control group completed the study. Analysis of variance revealed significant. and positive changes in measures of eight processes of change, self-efficacy, physical activity, and cardiorespiratory fitness in the treatment group at 24 weeks. All but one of these changes were maintained at 48 weeks. In the control group, significant changes occurred in only two processes of change, and no change occurred in self-efficacy, physical activity, or cardiorespiratory fitness at 24 or 48 weeks. Conclusion. A theory-based intervention is more likely to change the way obese women think and behave in relation to physical activity than a traditional exercise program that does not incorporate behavior change theory.