Introduction: A retrospective study was conducted with the aim of determining the factors that affect weight loss among post-bariatric surgery patients. Methods: A successful weight loss outcome in this study was defined as achieving at least 50% excess weight loss (EWL). Eligible participants were those who had undergone bariatric surgery at least two years prior to the study. Adherence to lifestyle recommendations post-bariatric surgery, binge eating, depression, and social support were assessed. Results: A total of 51 post-bariatric surgery patients were recruited with a mean post-operative period of 3.2±0.7 years. The mean preoperative weight of 116.6±28.8 kg and body mass index (BMI) 45.2±8.8 kg/m2 were significantly reduced to 86.6±21.0 kg and 33.6±6.7 kg/m2, respectively, during follow-up (p<0.001). A total of 66.7% of participants achieved successful weight loss following bariatric surgery, with a mean EWL of 73.6±21.9% and total weight loss (TWL) of 29.4±8.7%. According to multivariate regression analysis adjusted for age and gender, pre-operative weight (β=-1.580, p<0.05) and BMI (β=-1.398, p<0.05), rate of weight loss (β=1.045, p<0.01), and adherence to eating behaviour recommendations (β=0.177, p<0.05) were significant predictors of weight loss outcomes post-bariatric surgery. Conclusion: The lower pre-operative weight and BMI, the faster rate of weight loss and higher adherence towards eating behaviour advice were potential predictors of greater EWL and thus could increase the chance of successful weight loss maintenance post–bariatric surgery.