Morbid obesity is frequently associated with other characteristics of metabolic syndrome and is related to an increased risk of cardiovascular disease. This study aimed at evaluating time–course changes in body weight, body mass index (BMI), insulin sensitivity indexes and lipid profile in severely obese patients who underwent adjustable silicone gastric banding. We studied 19 obese subjects before and 6–36 months after surgery. An oral glucose tolerance test was performed in all non-diabetic patients. All subjects were evaluated using insulin sensitivity indexes (ISI-HOMA and QUICKI), lipid profile, and anthropometric parameters (WHR, WC, BMI), and body composition was assessed with bioelectrical impedance analysis (BIA). Most of the weight reduction occurred within the first 6–12 months, followed by near stabilisation or even weight regain. We found a significant decrease in fasting insulin, improvement in waist–hip ratio, reduction in BMI and fat mass percent. We observed an improvement in insulin sensitivity evaluated by means of ISI-HOMA and QUICKI. Bariatric surgery was an effective therapeutic approach for these obese patients because it reduced both weight and insulin resistance, along with improving metabolic parameters. Improvement in metabolic parameters appears to precede body weight reduction.