Respiratory function and the obesity paradox.
OBJECTIVE
Obese individuals have impaired respiratory function relative to their normal-weight counterparts. Despite these negative effects, obesity is paradoxically associated with better survival in individuals with chronic obstructive pulmonary disease (COPD). The purpose of this review is to describe this 'obesity paradox', to discuss the effects of obesity on respiratory function, and to speculate as to whether obesity-related alterations in respiratory mechanics can influence the natural history of COPD.


RESULTS
Given the known negative effects of obesity on respiratory physiology, it is reasonable to predict that obese COPD patients would be more likely to experience greater dyspnea and exercise intolerance relative to COPD patients of normal weight. However, recent evidence suggests that obese COPD patients have similar or better dyspnea scores during exercise and do not have diminished exercise capacity. These observations may be attributable to the fact that obese COPD patients have reduced operating lung volumes and higher inspiratory capacity to total lung capacity ratios than their lean COPD counterparts.


CONCLUSIONS
Obese patients with COPD do not appear to be at a disadvantage during exercise relative to lean COPD patients. Obesity may be associated with improved survival in COPD but specific mechanisms for this paradox remain to be elucidated.
Respiratory Investigation Unit, Department of Medicine, Queen's University, Kingston General Hospital, Kingston, Ontario, Canada.
Jordan A
JA
Guenette
Dennis
D
Jensen
Denis E
DE
O'Donnell
D004417:Dyspnea / Q000209:etiology / Q000503:physiopathology*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007320:Inspiratory Capacity / Q000502:physiology; D008168:Lung / Q000503:physiopathology*; D009765:Obesity / Q000150:complications / Q000503:physiopathology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications* / Q000401:mortality / Q000503:physiopathology