INTRODUCTION: Laparoscopic sleeve gastrectomy (LSG) became the most frequently performed bariatric procedure worldwide, gaining rapidly popularity thanks to its technical simplicity and the relatively good results. The aim of this Belgian-French study was to evaluate postoperative complications, weight loss, and resolution of obesity-related comorbidities after LSG, and identify predictive factors of weight loss failure. PATIENTS AND METHODS: A prospective multicenter study was conducted on all LSG performed during 2014 in 7 centers. Their demographic, preoperative, and postoperative data were prospectively collected and analyzed statistically. RESULTS: Overall 529 patients underwent LSG, with a mean preoperative weight and body mass index (BMI) of 118.9 ± 19.9 kg and 42.9 ± 5.5 kg/m2, respectively. Postoperative mortality was null and early postoperative morbidity was 6%, including 2.5% of gastric leakage. BMI significantly decreased to 31.1 kg/m2 and 30.0 kg/m2 at 1 and 3 years, respectively (p < .001). The mean %EWL was 77.2 and 74.6% at 1 and 3 years. A significant reduction in dyslipidemia (28.0-16.8%), obstructive sleep apnea (OSAS) (34.6-23.3%) and arterial hypertension (HTN) (30.4-20.2%) was observed after 3 years, but it does not concern diabetes and gastroesophageal reflux disease (GERD). At multivariate analysis, age > 50 years old, BMI >50 kg/m2 and previous laparoscopic adjustable gastric banding (LAGB) remained independent predictors of weight loss failure. CONCLUSIONS: LSG for morbid obesity is safe and effective. Satisfactory outcome after 3 years can be achieved regarding %EWL and some comorbidities such as dyslipidemia, OSAS, and HTN, but not diabetes and GERD. Age > 50 years old, BMI > 50 kg/m2 and previous LAGB were independent predictors of weight loss failure.