PurposeLaparoscopic Roux-en-Y Gastric Bypass (LRYGB) remains the most effective procedure to treat severe obesity with proven short- and intermediate-term benefits. The main goal is to describe the effects on weight and biochemical laboratory tests after long-term follow-up (11 years). Materials and MethodsA prospective cohort of adults with obesity treated with LRYGB between 2004 and 2010 in one center were studied. Patients with prior bariatric or upper digestive tract surgery, hiatal hernia >4 cm, alcoholism, or decompensated conditions were excluded. The study enrolled 123 patients, with a mean follow-up of 133 +/- 29 months and a 14% loss of participants. Results The percentage of Total Weight Loss (%TWL) at one, five, and eleven years was 30.3 +/- 8.4%, 29.1 +/- 6.9%, and 23.4 +/- 7%, respectively. Of the patients, 61.3% (65/106) maintained a %TWL >= 20 after eleven years. Recurrent Weight Gain (RWG) at five and eleven years was 2.6 +/- 11.4% and 11 +/- 11.5%, respectively. At the end of the follow-up, 31.1% (33/106) of patients had RWG >= 15%. Hypercholesterolemia and hypertriglyceridemia improved in 85.7% (54/63) and 90.2% (7/61) of the cohort, respectively. Remission of diabetes occurred in 80% of this subgroup. Gallstones developed in 28% of patients, and bowel obstruction due to internal hernia occurred in 9.4%. Anemia due to iron deficiency appeared in 25 patients. Conclusion After surgery, there is a significant and durable loss of weight, with a tendency for late Recurrent Weight Gain. Furthermore, the improvement in biochemical parameters is sustained over time, but surgery's adverse effects may appear later.