Effects of body composition and fat distribution on ventilatory function in adults.

Clinically, gross obesity is associated with disturbances of ventilatory function, but less severe obesity is not generally thought to have a significant effect on ventilatory function. The purpose of this report was to examine cross-sectional data to determine the effects of body composition and fat distribution on ventilatory function in 1235 adults (621 men and 614 women). Forced vital capacity (FVC) was used as a measure of ventilatory function and was adjusted for age, height, smoking, and bronchial symptoms in separate models for men and women. Body fat and fat-free mass were estimated from skinfold-thickness measurements. Adjusted FVC was not significantly associated with body mass or body mass index, but was negatively associated with percentage body fat in men (P = 0.0003) and women (P = 0.043) and positively associated with fat-free mass in men (P = 0.018) and women (P = 0.0001). Handgrip strength was positively associated with adjusted FVC in both sexes (P < 0.02), suggesting that the effect of fat-free mass may be mediated by muscular strength. Adjusted FVC was negatively associated with subscapular-skinfold thickness in both sexes (P < 0.0003) and with waist circumference (P = 0.01) and waist-to-hip ratio (P = 0.03) in men. Previous reports that considered only body mass index or body mass failed to distinguish the opposing effects of fat-free mass and fat mass on FVC.