Individuals with night eating syndrome (NES) display a time-delayed pattern of food intake, outside the natural circadian rhythm. High prevalence estimates have been reported among bariatric surgery candidates, and some evidence suggests that NES is positively associated with obesity, negatively associated with weight loss efficacy, and follows a chronic course. In order to evaluate current NES theory, and the association between NES and bariatric surgery, literature searches were conducted to identify relevant literature published in English up to 2005. Because of inconsistencies in NES characterization, and significant heterogeneity in study design and methods, a qualitative assessment of NES and its relation to bariatric surgery was then undertaken. Within the literature, variable NES definitions highlight the distinct lack of clarity as to which behavioral features constitute a clinically meaningful entity. Prevalence estimates appear high among persons seeking bariatric surgery; however, no consistent pre- or postoperative demographic, clinical, or psychological factors reliably differentiate NES from non-NES. Further examination of the clinical significance, correlates, and course of NES in general and surgical samples is important, given the link with obesity. The ways in which NES departs from "normal" eating behavior must be clarified. Behavioral and psychological traits of NES need elucidation, and the establishment of agreed diagnostic criteria is essential for research to move forward. Therapy options should focus on aspects of the syndrome that cause greatest impairment, distress, or health risk.
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