INSULIN SENSITIVITY IN POST-OBESE WOMEN

1. Both increased and decreased sensitivity to insulin has been propos ed to precede the development of obesity. Therefore, insulin sensitivi ty was measured during a 2 h hyperinsulinaemia (100 m-units min(-1) m( -2)) euglycaemic (4.5 mmol/l) glucose clamp combined with indirect cal orimetry in nine weight-stable post-obese women and in nine matched co ntrol women preceded by 12 h fasting after 48 h on a standardized diet . 2. Both glucose disposal rate (post-obese women, 9.5+/-2.2 mg min(-1 ) kg(-1), control women, 11.2+/-1.4 mg min(-1) kg(-1), not significant ) glucose oxidation (3.6+/-0.5 mg min(-1) kg(-1) versus 4.0+/- 0.7 mg min(-1) kg(-1), not significant) were similar in the two groups during the last 30 min of the clamp. Lipid oxidation also decreased similarl y during the clamp in the post-obese women (from 30.4+/-12 to 2.0+/-7 J min(-1) kg(-1)) and in the control women (from 33.6+/-11 to 5.4+/-8 J min(-1) kg(-1), not significant). Basal plasma concentrations of fre e fatty acids were similar, but at the end of the clamp free fatty aci ds were lower in the post-obese women than in the control women (139+/ -19 and 276+/-48 mu mol/l, P = 0.02). 3. We conclude that the insulin sensitivity of glucose metabolism is unaltered in the post-obese state . The study, however, points to an increased antilipolytic insulin act ion in post-obese subjects, which may favour fat storage and lower lip id oxidation rate post-prandially. The results suggest that alteration s in lipid metabolism may contribute to the explanation of the propens ity to obesity in susceptible individuals.