Lack of standard definitions of primary and secondary (non)responders after RYGB and SG makes it impossible to compare the literature. The aim was to analyze the different definitions used. MEDLINE® was searched for literature published between 01-07-2014 and 01-07-2017 concerning (1) patients who received a primary RYGB or SG and (2) the outcomes of primary and secondary (non)responders. One hundred twelve out of 650 papers were eligible. Forty out of 47 papers described a definition of weight loss success. Sixty-seven out of 112 papers mentioned weight loss failure of which 42 described a definition, in total 23 different definitions. Weight regain was mentioned in 77 papers; only 21 papers provided a definition. The recent literature regarding definitions of these outcomes is highly inconsistent. To compare the literature international consensus is required.
Keywords: Bariatric surgery; Gastric sleeve; Roux-en-Y gastric bypass; Weight loss failure; Weight loss success; Weight regain.