Assessment of disordered eating in bariatric surgery patients: diagnosis, measurement and psychometric evaluation

Eating disorders and disordered eating are prevalent in adults seeking surgical interventions for weight loss. While bariatric surgery is more effective than non-surgical interventions for weight loss and amelioration of physical health comorbidities, research findings are inconsistent regarding the impact of surgery on disordered eating and the impact of disordered eating on surgical outcomes. Not all bariatric surgery patients achieve optimal outcomes following surgery, and disordered eating may be one of the factors correlated with poorer outcomes. However, assessment in the existing literature has been plagued by methodological limitations, which limits the interpretation of current findings. Reliable and valid measurement is critical to inform assessment of suitability for surgery and enable identification of individuals who may benefit from treatment for disordered eating. This research systematically reviews and empirically examines the definition, diagnosis and measurement of disordered eating in bariatric surgery patients. Two systematic literature reviews were conducted to critically evaluate current approaches to the assessment of disordered eating in bariatric surgery candidates (pre-surgery) and patients (post-surgery). The reviews identify the definitions and diagnostic criteria applied to disordered eating, the measures used, and the psychometric evaluation of measures in the bariatric surgery population. The reviews also identify amendments to criteria and measures for the bariatric surgery population and offer a critique of the strengths and limitations of these measures when used for the purpose of assessment in this population. Results of the systematic reviews indicate that assessment of disordered eating is characterised by huge variability in measures and diagnostic criteria and extremely limited psychometric evaluation of measures in the bariatric surgery population. Informed by the systematic reviews, two empirical studies were conducted in patients before and after surgery to investigate the psychometric properties of disordered eating measures in the bariatric surgery population. Data from four hundred and five bariatric surgery candidates was collected via a pre-surgical battery of disordered eating measures (Eating Disorder Examination Questionnaire (EDE-Q), Questionnaire on Eating and Weight Patterns Revised (QEWP-R), Three Factor Eating Questionnaire (TFEQ), Clinical Impairment Assessment (CIA)), and the EDE interview. Approximately 12 months following surgery, a longitudinal subset of 108 bariatric surgery patients completed the same battery of self-report measures. Analyses were conducted to determine the factor structure, reliability, and construct and criterion validity of the measures. Results indicate that the CIA is the only reliable and valid measure when administered in its original form in bariatric surgery candidates. In post-surgical patients, none of the measures demonstrated validity for use in their original form. Consequently, revised factor structures and item-reduction were required in order for measures to meet minimum psychometric standards. Based on the psychometric data, the measure recommended for assessing the severity of eating-related pathology is a revised version of the EDE-Q, and the only measure recommended for diagnostic assessment is the EDE. For assessment of functional impairment, the CIA shows promise as a valuable measure but requires further refinement before being used in both pre- and post-surgical populations. The findings of this thesis have implications for research and clinical practice regarding the assessment of disordered eating in the bariatric surgery population. To date, the paucity of psychometric evaluation and lack of consensus on diagnostic criteria and measures have impacted the research literature reporting the prevalence of disordered eating, disordered eating outcomes following surgery, and the impact of disordered eating on surgical success. This thesis provides recommendations to inform the use of evidence-based assessments and improve the identification and assessment of disordered eating in this population. It is hoped that findings of this thesis will prompt the adoption of more reliable and valid assessment practices, leading to more accurate identification and treatment of disordered eating and consequently improved biopsychosocial outcomes for the bariatric surgery population