OBJECTIVE: To assess glucose homeostasis and weight loss in morbidly obese patients undergoing Silastic® ring sleeve gastrectomy. METHODS: This was a prospective clinical study. Thirty-three female patients with a mean body mass index (BMI) of 42.33 ± 1.50 kg/m² (range: 40-45 kg/m²), a mean age of 36.7 ± 9.4 years and a mean waist circumference of 118.7 ± 5.98 cm were included in this study. Type 2 diabetes mellitus was observed in 11 patients (33.3%), and glucose intolerance was observed in 4 patients (12.1%). Mean plasma fasting glucose levels were 109.77 ± 44.19 mg/dl (75-320) in the preoperative period. All Silastic® ring sleeve gastrectomy procedures were performed by the same surgical team using the same anesthetic technique. The patients were monitored for at least 12 months after surgery. RESULTS: The mean weight of the patients decreased from 107.69 ± 6.57 kg to 70.52 ± 9.36 kg (p < 0.001), the mean BMI decreased to 27.4 ± 2.42 kg/m² (p < 0.001), and the mean waist circumference decreased to 89.87 cm ± 6.66 (p < 0.001) in the postoperative period. Excess BMI loss was 86.5 ± 14.2%. Fasting glucose levels were reduced to 80.94 ± 6.3 mg/dl (p < 0.001). Remission of diabetes and glucose intolerance was observed in all patients. CONCLUSION: Silastic® ring sleeve gastrectomy was effective in promoting weight loss, waist circumference reduction and control of glucose homeostasis in morbidly obese patients.