Fuel metabolism in anorexia nervosa and simple obesity

To examine insulin sensitivity and the relative contribution of different fuels to energy metabolism in anorexia nervosa and obesity, we measured oxidation (indirect calorimetry) of glucose, lipids, and proteins in the basal state and during an insulin clamp (+45 mU/m2.min) in 11 women with anorexia nervosa (age, 25 +/- 3 years; body mass index [BMI], 13.6 +/- 0.4 kg/m2; fat mass, 15.7% +/- 1.6%), eight obese women (age, 31 +/- 3; BMI 36.0 +/- 1.5; fat mass, 47.1% +/- 1.9%), and eight controls (age, 26 +/- 3; BMI, 21.8 +/- 0.9; fat mass, 25.7% +/- 3.6%). Expressed per lean body mass, (LBM), glucose disposal was equally reduced in anorectics (7.53 +/- 0.62 mg/kg LBM.min) and obese (6.80 +/- 1.07 mg/kg LBM.min) compared with controls (10.64 +/- 0.69 mg/kg LBM.min; P less than .01). The reduction in glucose disposal in anorectics was primarily due to a significant (P less than .01) reduction in glucose storage, while glucose oxidation was normal. In obese women, both storage and oxidation of glucose were reduced compared with controls (P less than .01). Basal energy expenditure was similar in anorectic, obese, and control subjects (20.6 +/- 1.00, 23.7 +/- 0.56, 23.2 +/- 1.36 cal/kg LBM.min, respectively). However, the contribution of glucose, lipids, and proteins to basal energy expenditure differed between anorectic (62%, 16%, 22%), obese (26%, 58%, 16%), and control (30%, 54%, 16%) subjects (P less than .05 v all). In conclusion, in anorexia nervosa, insulin stimulates glucose oxidation more than storage. In obesity, both components of insulin-stimulated glucose metabolism are impaired.(ABSTRACT TRUNCATED AT 250 WORDS)