Aim and Background: One of the main concerns of health psychology is the follow-up of patients of treatment adherence. Lifestyle self-efficacy related to weight and psychological distress, are the factors that play important roles in explaining the rate of treatment adherence in obesity surgery. The purpose of this study was to determine the mediation role of treatment adherence in the relationship between weight-related lifestyle self-efficacy, psychological distress and weight loss in obese patients undergoing sleeve gastrectomy surgery method.

Methods and Materials: The research method was descriptive correlational and the statistical population included all obesity patients who had undergone sleeve gastrectomy surgery at the Endocrine and Metabolism Research Center and 200 of them were selected by available sampling method. Research instruments included Body Mass Index, Weight Efficacy Lifestyle Questionnaire, Depression, Anxiety, Stress Scale- short form, and General Adherence Scale. Data were analyzed using structural equation modeling method.

Findings: The results of this study showed that direct effect of self-efficacy on weight loss (P<0.01, β=0.169) and indirect effect treatment adherence (P<0.01, β=0.77) were significant. The direct effect of psychological distress on weight loss (P<0.05, β=-0.186) and indirect effect of psychosocial distress were significant (P<0.05, P=0.069).

Conclusions: It seems that self-efficacy reduces psychological distress by influencing the person and improving her resilience, leading to increased follow-up and weight loss.