Purpose Sleeve gastrectomy (SG) is an effective treatment for extreme obesity; however, long-term weight loss outcomes remain largely understudied. We aimed to examine the long-term weight changes following SG and patient characteristics and lifestyle patterns related to weight loss outcomes. Materials and Methods Data from medical records of patients operated in a tertiary university medical center between 2008 and 2014 were reviewed, along with information derived from a telephone questionnaire. Information included the following: current medical status, medications, side effects, behavior, lifestyle habits, and weight changes. Results A total of 212 patients (69.3% females) were included, with a median follow-up duration of 8 years post-SG. Mean age and baseline body mass index (BMI) of participants were 39.7 ± 12.0 years and 42.2 ± 4.9 kg/m 2 , respectively. Mean BMI, percentage excess weight loss, and percentage total body weight loss were 33.1 ± 6.1, 55.5 ± 27.5%, and 21.7 ± 10.7%, respectively. Higher baseline BMI was found to be the strongest independent predictor for insufficient weight loss ( OR  = 0.90, P  = 0.001, 95% CI 0.85, 0.96). Sweetened beverage intake, usage of psychiatric medications, higher initial BMI, and lower age were significant predictors for increased weight gain from nadir weight ( P  < 0.0001, P  = 0.005, P  = 0.035, and P  < 0.0001, respectively). Conclusions SG patients were found to maintain a notable long-term weight loss. Nevertheless, weight regain and insufficient weight loss were prevalent in the long-term post-operative period, and were related to certain lifestyle patterns. Clinical practice should emphasize the relationship between post-operative weight loss outcomes and specific behaviors. Efforts should be made to educate patients on the need for lifelong follow-up and support. Graphical abstract