Glucose Handling in Morbid Obesity and the Effects of Surgically Induced Weight Loss

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Abstract
Morbid obesity is associated with glucose intolerance. We studied the rate of glucose turnover in 18 morbidly obese individuals and compared the results to 10 normal weight controls using the technique of the hyperglycemic clamp. Rate of glucose turnover (mg/kg/min) was defined as metabolic clearance of glucose and corresponding plasma immunoreactive insulin values were determined. The ratio of metabolic clearance of glucose to plasma insulin is a reflection of endogenous insulin sensitivity. Patients were studied again 3 months following jejunoileal bypass and gastroplasty. Fasting glucose was similar for all groups. Fasting immunoreactive insulin was 16.8 ± 5 μU/ml in preoperative obese, 4.3 ± 0.2 in controls, 6.8 ± 0.6 in postoperative jejunoileal bypass, and 6.2 ± 0.3 in postoperative gastroplasty. The difference between postoperative groups was not significant at 3 months. The jejunoileal bypass group at 1 yr gave similar results to the immediate postoperative findings. In normals the value of metabolic clearance of glucose was 3.9 ± 0.7 mg/kg/min and in the obese it was 2.05 ± 0.2 (p < 0.05). No significant improvement occurred postoperatively. Mean of the immunoreactive insulin values from 60 to 120 min was greater in preoperative obese than controls, 44.0 compared to 13.6 μU/ml (p < 0.05). A highly significant postoperative lowering occurred in both groups, jejunoileal bypass 20.7 μU/ ml, gastroplasty 22.4 μU/ml, but the difference between the surgical groups (jejunoileal and gastroplasty) is not significant. The ratio of metabolic glucose clearance to plasma insulin followed a similar pattern due primarily to the substantial decrease in insulin levels. At 1 yr after jejunoileal bypass the patients had similar findings to their immediate postoperative results. There appears to be a defect in glucose metabolism in morbidly obese individuals which does not respond to weight loss even though insulin levels drop. When the ratio of metabolic clearance of glucose to plasma insulin is compared to weight loss no correlation exists suggesting that the defect in glucose handling is not completely reversible with weight loss. (Journal of Parenteral and Enteral Nutrition 8:660–664, 1984)