Weight-Related Negative Experiences, Internalized Weight Stigma, and General Self-Efficacy in Adults with Obesity: An Explanatory Sequential Mixed-Methods Study

Background/Objectives: Weight stigma may be experienced externally and internalized as self-directed negative beliefs, with consequences for psychological resources and healthcare use. This study examined associations among weight-related negative experiences, internalized weight stigma, and general self-efficacy, and explored how these relationships were reflected in adults receiving obesity care. Methods: An explanatory sequential mixed-methods study was conducted at a university-affiliated multidisciplinary obesity and diabetes center in Türkiye. In the quantitative phase, 435 adults with obesity were consecutively recruited during the predefined study period and completed researcher-developed items on weight-related experiences, the Modified Weight Bias Internalization Scale, and the General Self-Efficacy Scale. Multivariable linear regression and bootstrap-based indirect-effect analysis were performed. Subsequently, 20 participants underwent semi-structured interviews and thematic analysis. Findings were integrated using a joint display. Results: Weight-related discrimination or negative experiences in social or workplace settings were reported by 27.8% of participants, while 11.5% reported weight-related negative healthcare experiences. Of those reporting negative healthcare experiences and responding to the follow-up item, 77.1% stated that subsequent healthcare use had been affected. Social/workplace negative experiences were associated with higher internalized weight stigma scores (B = 0.814, 95% CI 0.525–1.103) and lower general self-efficacy scores (B = −4.238, 95% CI −6.925 to −1.551). The hypothesized indirect association through internalized weight stigma was significant (B = −2.403, 95% CI −3.569 to −1.353). Qualitative themes addressed obesity as label and identity, judgment and internalization, weight overshadowing care, and conditional confidence. Conclusions: Weight-related negative experiences, internalized weight stigma, and lower general self-efficacy were interrelated in this treatment-seeking population. Qualitative findings highlighted interpersonal and structural barriers to care.