Abstract
It has been proven that surgery is more effective than non-surgical treatment in obese patients. However, this approach has several disadvantages, especially long-term weight loss. Weight loss failures can be broadly classified into two categories; insufficient weight loss (poor responder) and weight regain. However, a unified definition has not been established yet for each category, and there is no clear standard for the post-surgery time point to be used to assess weight loss failure. In addition, analyzing factors that contribute to weight loss failure will lead to strategies for reducing it. Therefore, many researchers have been interested in this subject and have published conflicting results. This review presents a definition for and describes the mechanisms and predictors of weight loss failure after bariatric surgery.