Energy Balance in Chronic Obstructive Pulmonary Disease

A substantial number of patients with chronic obstructive pulmonry disease (COPD) suffer from gradual and significant weight loss during the natural course of their illness. The aim of this study was to determine the contribution of resting energy expenditure (REE) and energy intake (E-intake) to weight loss in 80 patients with stable COPD: age (mean ± SEM) 65 ± 3 yr and FEV1 1.0 ± 0.1 L. A total of 39 patients exhibited a continued weight loss in the previous year. REE measured with a ventilated hood system was significantly (p < 0.005) higher in weight-losing compared to weight-stable patients when values were normalized for predicted metabolic rate (117 ± 3 and 108 ± 2%, respectively) or kg fat-free mass using bioelectrical impedance (FFM-BI): 35.0 ± 0.8 and 31.8 ± 0.6 kcal/kg, respectively). Normalized values of E-intake were not significantly different between weight-losing and weight-stable patients. REE/FFM-BI correlated significantly with FEV1 (r = 0.22, p < 0.05), maximal inspiratory mouth pressure (Pi max; r = 0.35, p < 0.001), and E-intake/FFM-BI (r = 0.48, p < 0.001). Classification in three subgroups by severity of disease, (1) FEV1 > 35%, (2) FEV1 ⩽ 35%, and (3) PaO2 < 7.3 kPa, revealed a higher prevalence of weight loss in the more compromised groups and a significantly decreased (p < 0.05) E-intake in the hypoxemic patients. A gradual depletion of percentage ideal body weight (p < 0.001), midarm circumference (p < 0.01), midarm muscle circumference (p < 0.001), and creatinine height index (p < 0.001) and a decrease in respiratory muscle strength (p < 0.005) were associated with increasing severity of disease. Our results indicate that a failure of an adaptive response to undernutrition and an inadequate dietary intake for energy expenditure are two contributing factors to weight loss in COPD.