Aim of this study was to investigate relationship between preoperative psychological factors and % total weight loss after gastric bypass. 76 adult patients scheduled for bariatric surgery were preoperatively asked to complete anxiety and depression Hamilton scales and Toronto Alexithymia Scale. At 3- and 6-month follow-up, body weight was assessed. At 6-month follow-up, alexithymic patients showed a poorer % total weight loss compared with non-alexithymic patients (p = .017), and moderately depressed patients showed a lower % total weight loss compared with non-depressed patients (p = .011). Focused pre- and postoperative psychological support could be useful in bariatric patients in order to improve surgical outcome.