Improvement of insulin resistance after obesity surgery: a comparison of gastric banding and bypass procedures.

BACKGROUND: Obesity is a major risk factor for the development of type 2 diabetes mellitus (T2DM). Insulin resistance (IR) is considered the pathologic link between T2DM and obesity. The mechanism in improving T2DM after bariatric surgery remains speculative. This trial assessed the effect of duodenal jejunal exclusion on the resolution of IR in gastric banding and gastric bypass procedures.

METHODS: 660 patients with complete biochemical and clinical data at baseline and at 3 years were selected for analysis. There were 197 males and 463 females. The mean age was 31.5 years (18-64) and mean BMI was 41.4 (32-77). There were 544 patients who received laparoscopic gastric bypass, and 116 patients received laparoscopic gastric banding. IR was measured by homeostatic model assessment (HOMA) index (HI), that can be calculated as HI = plasma glucose (mmol/l) x insulin (UI/ml)/22.5. HI was measured before surgery and 1, 3, 6, 12, 24, and 36 months after surgery.

RESULTS: Of the 660 individuals, 517 (78.4%) had IR. The mean HI was 7.62 +/- 13.13. The HI was correlated with BMI, waist circumference, insulin resistance, hyperlipidemia, inflammatory indicators, and abnormal liver enzymes. Before surgery, the HI was 7.92 +/- 14.18 for the bypass group and 6.27 +/- 6.47 for the banding group. After surgery, the HI began to lower in both groups, and this reduction was maintained during follow-up. At 36 months after surgery, mean percentage of excess weight loss (%EWL) was 70.5% for the bypass group and 41.9% for the banding group. The HI was 1.00 +/- 0.79 for bypass and 1.51 +/- 1.25 for banding. The bypass patients had a better and faster weight reduction, but the HI was similar between the two groups at the same weight reduction percentage.

CONCLUSION: IR is common in morbidly obese patients. Both gastric banding and gastric bypass are effective for the reverse of IR in these patients. It seems that the effect is related to the absolute weight loss rather than different surgical procedures. There is no duodenal jejunal exclusion effect on IR resolution was observed in this study.