The Effect of Severe Undernutrition and Subsequent Refeeding on Whole‐Body Metabolism and Protein Synthesis in Human Subjects

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Abstract
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/m2 in the anorexia patients and 13.81 ± 0.40 kg/m2 in the disease patients (controls 23.71 ± 0.72 kg/m2; 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 ± 0.03; 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).