Glucose utilization in morbidly obese subjects before and after weight loss by gastric bypass operation

OBJECTIVE: To investigate the effect of weight reduction induced by gastric bypass operation (GBO), on the peripheral resistance to insulin ire extremely obese subjects. DESIGN: A three-stage euglycemic clamp was applied to assess the metabolic clearance rate of glucose (g-MCR) in lean controls and in obese subjects, prior to and 6 - 12 months post operation. SUBJECTS: Six obese subjects (four obese normoglycemics-ON and two obese non-insulin dependent diabetics-OD) before and after GBO and six healthy, lean controls (LC) were compared. MAIN OUTCOME MEASURES: Body mass index after GBO, metabolic clearance rate of glucose under increasing insulin concentrations. RESULTS: GBO resulted in a significant change in body mass index from a pre-operation value (mean ± s.d.) of 45.0 ± 8.5 to 30.4 ± 5.9 kg m^-2 and remained significantly greater than controls (23.3 ± 2.3 kg m^-2). Glucose MCR increased from a mean baseline value of 3.0 ± 1.6 to 6.7 ± 3.9 ml kg^-1 min^-1 at post GBO (P) (P < 0.02). Similar effects were obtained under the two higher insulin concentration. CONCLUSIONS: GBO resulted in a massive reduction in BMI, that still remained above normal controls. This could explain the effect of weight reduction to decrease, but not completely reverse, peripheral resistance to insulin associated with obesity.