Am J (Yin Nutr 1993:57:85 1-6. Printed in USA. © 1993 American Society for Clinical Nutrition 851 Decreased glucose-induced thermogenesis at the onset of obesity1’2

ABSTRACT ’ To investigate the possible existence ofa defect of thermogenesis at the onset of obesity, we studied glucose-induced thermogenesis (GIT) during an oral glucose-tolerance test (OGTT) ( I g/kg body wt) in I 2 women who were at the onset ofobesity (group A) compared with 12 long-standing obese women (group B) and 8 lean control subjects. During OGTT hyperinsulinemia and glucose intolerance were measured in group B. suggesting an insulin-resistant state, but not in group A. A similar defect in GIT occurred in both obese groups (8.9 ± 1.5 % in control subjects vs 4.2 ± 1.1 % in group A and 4.3 ± 1.0 % in group B. P < 0.05) despite the absence of alteration in nonoxidative glucose metabolism. We conclude that a decrease in GIT already exists at the onset ofobesity, which supports the hypothesis ofa possible involvement ofthis defect in the genesis of obesity..1tn J C/in Nuir I 993:57:85 1-6. KEY WORDS Obesity, glucose-induced thermogenesis, onset of obesity, indirect calorimetry, oral glucose-tolerance test. insulin resistanc