The effect of severe undernutrition and subsequent refeeding on whole-body metabolism and protein synthesis in human subjects

Background: To determine the consequences of severe undernutrition and refeeding on whole-body metabolism and protein synthesis. Methods: Respiratory quotient (RQ), resting energy expenditure (REE), and whole-body protein synthesis (WBPS) were assessed in undernourished patients, with anorexia nervosa (n = 8) or with coexistent disease (n = 17). Results were compared with 17 healthy controls. Six anorexic patients and 13 disease patients consented to study after nutrition support. Results: Mean body mass index was 12.46 +/- 0.53 kg/m(2) in the anorexia patients and 13.81 +/- 0.40 kg/m(2) in the disease patients (controls 23.71 +/- 0.72 kg/m(2); p <.001). Compared with controls, RQ was similar in anorexia patients (0.85 +/- 0.05 vs 0.90 +/- 0.05) but lower in the disease patients (0.76 +/- 0.03 vs 0.90 +/- 0.05; p =.02). REE was lower in the patients (anorexia 1058 +/- 134.0 kcal/d, disease 1189 +/- 101.4 kcal/d vs 1828 +/- 89.76 kcal/d; p <.001); however, expressed as kcal/kg/d, it was higher (anorexia 32.17 +/- 4.25, disease 31.30 +/- 2.14 vs 25.07 +/- 1.00; p <.05). WBPS was lower in the patients (anorexia 140.9 +/- 10.54 g/d, disease 119.8 +/- 8.57 g/d vs 305.0 +/- 21.64 g/d; p <.001); however, when expressed as g/kg/d, the anorexia patients were similar to controls, whereas the disease patients were lower (3.11 +/- 0.24 vs 4.27 +/- 0.32; p <.05). Refeeding increased RQ in the disease patients (0.84 +/- 0.03 vs 0.76 +/- 0.08; p <.05), and normalized REE (anorexia 27.65 +/- 3.05 kcal/kg/d, disease 28.90 +/- 1.85 kcal/kg/d). WBPS increased in the disease patients (173.6 +/- 16.38 g/d vs 116.5 +/- 10.15 g/d; p <.01). Conclusions: Undernutrition is associated with increased REE (kcal/kg/d). Reduction in RQ and protein synthesis (g/kg/d) was evident in those patients with coexistent disease. Refeeding resulted in normalization of RQ, REE (kcal/kg/d), and protein synthesis (g/kg/d).