Anorexia nervosa (AN) is a state of self-induced malnutrition characterized by a marked pursuit of thinness and the fear of obesity. Although low fasting blood glucose and insulin have been demonstrated, there is contradictory data on insulin sensitivity and a lack of information about insulin metabolism and its metabolic effects in AN. Insulin sensitivity, kinetics, and metabolic effects were measured using the euglycemic clamp in nine females with AN (age 25.2 +/- 1.9 years and 70.6 +/- 2.2% ideal body weight), and the results compared with seven female normal controls (NC) (age 23.6 +/- 1.0 years and 92.7 +/- 2.5% ideal body weight). Fasting plasma glucose (FPG), immunoreactive insulin (IRI), and C-peptide were significantly lower in AN as compared to NC (84.3 +/- 1.5 v 91.5 +/- 1.7 mg dL-1, 9.3 +/- 1.0 v 13.5 +/- 1.4 microU mL-1, and 0.26 +/- 0.03 v 0.41 +/- 0.02 pmol mL-1) (P less than 0.05). During the glucose clamp, the glucose metabolized (M), the metabolic clearance rate of glucose (MCRg), and the glucose metabolized per unit of insulin (M/I ratio) were all higher in AN as compared to NC (M, 8.7 +/- 1.2 v 6.9 +/- 0.6 mg min-1 kg-1; MCRg, 9.9 +/- 1.5 v 7.4 +/- 0.6 mL min-1 kg-1; M/I ratio, 8.6 +/- 1.6 v 5.0 +/- 0.3 mg min-1 kg-1/microU mL-1 X 100), but only the M/I ratio attained statistical significance (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)