The effects of weight loss in obese subjects on the thermogenic, metabolic and haemodynamic 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/m2/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/m2 and after weight loss 31.4 +/- 2.3 kg/m2). 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.