THE EFFECTS OF WEIGHT-LOSS IN OBESE SUBJECTS ON THE THERMOGENIC, METABOLIC AND HEMODYNAMIC-RESPONSES TO THE GLUCOSE CLAMP

The aim of this work was to examine the effects of weight loss in obese subjects on the thermogenic, metabolic and cardiovascular responses to a glucose clamp. Resting measurements were made, followed by a hyperinsulinaemic (100 mU/m(2)/min) euglycaemic clamp (4.5 mmol/l). The subjects were six healthy, obese subjects (mean body mass index before weight loss 37.0 +/- 1.7 kg/m(2) and after weight loss 31.4 +/- 2.3 kg/m(2)). The following measurements were made: indirect calorimetry, blood pressure, heart rate, forearm blood flow, plasma catecholamines, plasma deuterated glucose turnover before and during a glucose clamp. Glucose disposal during the clamp increased from 2.53 +/- 0.40 to 3.31 +/- 0.42 mmol/min after weight loss (P < 0.01). Glucose-induced thermogenesis rose from 0.15 +/- 0.09 to 0.50 +/- 0.12 kJ/min (P < 0.05). The apparent cost of glucose storage was not significantly different from zero prior to weight loss, but increased to 11.0 +/- 2.2% after weight loss. In response to the clamp endogenous glucose production was suppressed by 66 +/- 7% initially and this was not affected by weight loss. Weight loss was accompanied by increased peripheral insulin sensitivity and glucose-induced thermogenesis, but it did not affect hepatic insulin sensitivity.