ABSTRACT
BACKGROUND: Obesity alters breathing mechanics during exercise. Weight loss improves lung function at rest, but the effect of weight loss, especially regional fat loss, on exercise breathing mechanics is unclear. We hypothesized that weight loss, especially a decrease in abdominal fat, would improve breathing mechanics during exercise because of an increase in end-expiratory lung volume (EELV). METHODS: Nine obese men were studied before and after weight loss (13% ± 8% of total fat weight, mean ± SD). Subjects underwent pulmonary function testing, underwater weighing, fat distribution estimates (MRI), and graded cycle ergometry before and after a 12-week diet and exercise program. In seven men, esophageal and gastric pressures were measured. The effects of weight loss were analyzed at rest, at ventilatory threshold (VTh), and during peak exercise by dependent Student t test, and the relationship among variables was determined by correlation analysis. RESULTS: Subjects lost 7.4 ± 4.2 kg of body weight (P < .001), but the distribution of fat remained unchanged. After weight loss, lung volume subdivisions at rest were increased (P < .05) and were moderately associated (P < .05) with changes in chest, waist, and hip circumferences. At VTh, EELV increased, and gastric pressure decreased significantly (P < .05). The changes in waist circumference, hip circumference, BMI, and sum of chest, waist, and hip circumferences were also consistently and significantly correlated (P < .05) with changes in gastric pressure during exercise at VTh. CONCLUSIONS: Modest weight loss improves breathing mechanics during submaximal exercise in otherwise healthy obese men, which is clinically encouraging. Improvement appears to be related to the cumulative loss of chest wall fat.
Subject(s)
Exercise , Obesity/physiopathology , Respiratory Mechanics , Weight Loss , Adiposity , Functional Residual Capacity , Humans , Inspiratory Capacity , Lung Volume Measurements , Magnetic Resonance Imaging , Male , Obesity/diet therapy , Obesity/pathology , Pulmonary Gas Exchange , Total Lung Capacity , Vital CapacityABSTRACT
BACKGROUND: Although obesity significantly reduces end-expiratory lung volume (EELV), the relationship between EELV and detailed measures of fat distribution has not been studied in obese men and women. To investigate, EELV and chest wall fat distribution (ie, rib cage, anterior subcutaneous abdominal fat, posterior subcutaneous fat, and visceral fat) were measured in lean men and women (ie, < 25% body fat) and obese men and women (ie, > 30% body fat). METHODS: All subjects underwent pulmonary function testing, hydrostatic weighing, and MRI scans. Data were analyzed for the men and women separately by independent t test, and the relationships between variables were determined by regression analysis. RESULTS: All body composition measurements were significantly different among the lean and obese men and women (p < 0.001). However, with only a few exceptions, fat distribution was similar among the lean and obese men and women (p > 0.05). The mean EELV was significantly lower in the obese men (39 +/- 6% vs 46 +/- 4% total lung capacity [TLC], respectively; p < 0.0005) and women (40 +/- 4% vs 53 +/- 4% TLC, respectively; p < 0.0001) compared with lean control subjects. Many estimates of body fat were significantly correlated with EELV for both men and women. CONCLUSIONS: In both men and women, the decrease in EELV with obesity appears to be related to the cumulative effect of increased chest wall fat rather than to any specific regional chest wall fat distribution. Also, with only a few exceptions, relative fat distribution is markedly similar between lean and obese subjects.
