Effects of Obesity on Lung Function

Obesity causes significant changes in lung function, many of which are secondary to the reduction in operating lung volume which, in turn, may be due to various potential mechanisms affecting the airways, lung parenchyma and chest wall. Mass loading of the chest wall due to excessive adipose tissue may account for much of the decrease in operating lung volume and secondary changes in lung function. However, some studies have reported changes in airway function associated with obesity that are independent of lung volumes, which suggest that there are other mechanisms occurring, although the nature of these mechanisms has not been defined. It is unclear how the overall effects of obesity as measured by lung function influence respiratory symptoms, which are commonly reported in obese individuals. The interaction between the physiologic effects of obesity and the lung and disease is complex and also incompletely understood. However, an understanding of the known physiological effect of obesity on lung function is useful for clinicians caring for patients who have respiratory disease, because it allows better evaluation of how much to attribute symptoms and lung function impairment to obesity per se, as opposed to uncontrolled airway disease such as asthma or COPD.