The use of weight loss surgery is progressively increasing, and in recent years, restrictive bariatric surgery procedures have been more often used. Although thought to be associated with a lower incidence of post-operative side effects than malabsorpitive surgery, some cases of micronutrients deficiency have been reported because of an acquired thiamine deficiency; in this clinical setting, some cases of Wernicke encephalopathy (WE) have been described. Major determinants and predictors of this major neurological complication are currently unknown. The aim of this systematic review was to analyse literature data in order to address this issue. The main result of our systematic review was that persistent vomiting is the major determinant of WE in patients undergoing restrictive weight loss surgery. In addition, early thiamine supplementation can rapidly improve the clinical conditions, avoiding permanent deficiencies. On the other hand, given the wide variability of clinical and demographic characteristics, definite prognostic factors of WE occurrence and of clinical outcome cannot be identified. In conclusion, although our results are suggestive, further ad hoc prospective studies evaluating changes in micronutrients levels according to different types of surgery are needed. Copyright © 2014 John Wiley & Sons, Ltd and Eating Disorders Association.