Background: Laparoscopic sleeve gastrectomy (LSG) is gaining in popularity and has become the fastest growing bariatric operation at this time. However, there is a lack of studies that help to predict optimal outcomes. Our study is aimed at identifying preoperative factors that are predictive of successful weight loss after LSG. Methods: A total of 100 consecutive patients undergoing LSG were enrolled over 36 months. Socioeconomic and demographic factors were prospectively collected for patients undergoing LSG. The primary endpoint was percent of excess weight loss at 1 year (EWL1). The cutoff point to define inadequate weight loss was set as mean 1 year EWL-1 SD. Logistic regression was used to identify independent preoperative factors associated with successful weight loss. Results: Mean EWL1 was 65.723.5%. Therefore, adequate weight loss was defined as EWL>42.2%. According to this cutoff, 82 patients (82%) achieved successful weight loss 1 year after LSG. Age, sex, marital status, number of children, employment status, smoking status, education, and history of binge eating or depression were not correlated with weight loss outcome. Preoperative body mass index (BMI) remained an independent predictor of success in the multivariate logistic regression model. Average BMI for the successful group was 47.5 versus 53.5 for the inadequate EWL group (p=0.004). A unit increase in BMI is associated with a 1.1-fold increase in the log hazard rate (HR) of having an inadequate EWL (HR 1.1; 95% CI: 1-1.1; p=0.008). Conclusions: Patients with a BMI lower than 50 have the highest odds of achieving successful weight loss, and they should therefore represent the ideal target population for LSG.