Body composition and lung function

Abstract

A growing body of evidence indicates that excess body weight is associated with a wide range of health conditions, including respiratory diseases. Cross-sectional studies have demonstrated an inverse relationship between body mass index and pulmonary function evaluated by spirometry. Longitudinal studies have shown that increases in body weight can lead to a reduction in pulmonary function. Although the influence of obesity on pulmonary function tests has been examined, there are limited studies that evaluate the influence of body fat distribution on pulmonary function tests in overweight and moderate obesity. It has been previously shown that body fat distribution has an effect on pulmonary function. In particular, the excess of visceral fat has a negative effect on lung function and is inversely associated with chest wall compliance. A consistent negative association between waist circumference and pulmonary function has been demonstrated in normal weight, overweight and obese subjects, suggesting that the fat mass stored in the abdominal cavity, particularly visceral fat, most likely directly impedes the descent of the diaphragm leading to primarily restrictive respiration impairment. An increased neck circumference has been suggested as a better sign of obstructive sleep apnoea than waist and BMI. In the elderly the amount of body fat and a central pattern of fat distribution correlate negatively with lung function, whereas the amount of fat-free mass correlates positively with lung function. The age-related combination of fat free mass loss and fat gain, so called "sarcopenic obesity", may have additive negative effects on pulmonary function.