Nutritional status is related to fat-free mass, exercise capacity and inspiratory strength in severe chronic obstructive pulmonary disease patients

ABSTRACT

INTRODUCTION: Being overweight or obese is associated with a higher rate of survival in patients with advanced chronic obstructive pulmonary disease (COPD). This paradoxical relationship indicates that the influence of nutritional status on functional parameters should be further investigated. OBJECTIVE: To investigate the impact of nutritional status on body composition, exercise capacity and respiratory muscle strength in severe chronic obstructive pulmonary disease patients. METHODS: Thirty-two patients (nine women) were divided into three groups according to their body mass indices (BMI) overweight/obese (25 < BMI < 34.9 kg/m², n=8), normal weight (18.5 < BMI < 24.9 kg/m², n=17) and underweight (BMI <18.5 kg/m², n=7). Spirometry, bioelectrical impedance, a six-minute walking distance test and maximal inspiratory and expiratory pressures were assessed. RESULTS: Airway obstruction was similar among the groups (p=0.30); however, overweight/obese patients had a higher fat-free mass (FFM) index [FFMI=FFM/body weight² (mean±SEM 17±0.3 vs. 15±0.3 vs. 14±0.5 m/kg², p<0.01)], exercise capacity (90±8 vs. 79±6 vs. 57±8 m, p=0.02) and maximal inspiratory pressure (63±7 vs. 57±5 vs. 35±8 percent predicted, p=0.03) in comparison to normal weight and underweight patients, respectively. In addition, on backward multiple regression analysis, FFMI was the unique independent predictor of exercise capacity (partial r=0.52, p<0.01). CONCLUSIONS: Severe chronic obstructive pulmonary disease (COPD) patients who were overweight or obese had a greater FFM, exercise capacity and inspiratory muscle strength than patients with the same degree of airflow obstruction who were of normal weight or underweight, and higher FFM was independently associated with higher exercise capacity. These characteristics of overweight or obese patients might counteract the drawbacks of excess weight and lead to an improved prognosis in COPD.