OBJECTIVES:

Self-regulation is thought to play a role in overcoming barriers to weight management behaviour changes. This research assessed the extent that relationship is manifested through associated changes in self-efficacy, and effects based on degree of obesity.

DESIGN:

Data sets from three previous studies of the present research group were utilized. After assessment of change scores using repeated-measures ANOVA, mediation and moderation analyses assessed effects of changes in self-regulatory skill usage on changes in physical activity and fruit/vegetable intake through self-efficacy changes. Moderating effects of BMI were then assessed.

METHODS:

Women with body compositions ranging from non-obese (BMI < 30 kg/m2 ) to those with morbid obesity (BMI ≥ 40 kg/m2 ) were administered similar cognitive-behavioural treatments, and assessed on theory-based psychosocial and behavioural measures over 6 months.

RESULTS:

From baseline to Month 6, changes in self-regulation for physical activity and eating, physical activity behaviours, fruit/vegetable intake, and self-efficacy for controlled eating were significant in non-obese women (n = 48) and women with Class 1 (n = 43), Class 2 (n = 70), and Class 3 (n = 48) obesity. Positive effects were smaller in exercise self-efficacy. For each of the BMI-based groups, changes in self-efficacy significantly mediated the prediction of physical activity and fruit/vegetable intake by changes in self-regulation. In aggregated data, BMI significantly moderated the prediction of change in physical activity (higher BMI associated with a stronger association), but not fruit/vegetable intake, within those models.

CONCLUSION:

Increasing self-regulatory skills to overcome lifestyle barriers was found to be important for fostering improved weight loss behaviours, especially in the treatment of higher degrees of obesity in women. Statement of contribution What is already known on this subject? Self-efficacy is a malleable factor that predicts behaviour change within multiple theories. Learned self-regulatory skills may effectively deal with lifestyle barriers associated with improvements in weight management behaviours. Increased physical activity and fruit/vegetable consumption predicts success with weight loss. What does this study add? Much of self-regulation's effect on physical activity and eating behaviours is through its impact on self-efficacy. Weight management treatments should emphasize self-regulatory skills development over simply health education. Effects of interrelations of self-regulation and self-efficacy are more effective as female weight increases.