EFFECTS OF WEIGHT LOSS ON FAT DISTRIBUTION AND EXERCISE MECHANICS IN OBESE MEN

Abstract

Obesity decreases resting lung volumes, particularly end-expiratory lung volume (EELV), which is an important factor regarding normal breathing mechanics during exercise. The effect of weight loss on fat distribution (i.e., upper rib cage, abdominal, and peripheral) and exercise mechanics has not been studied. PURPOSE To examine the effect of weight loss on fat distribution and breathing mechanics during exercise, we studied 9 obese men before (38 ± 4% body fat, mean ± SD) and after weight loss (35 ± 3%). We hypothesized that weight loss would alter fat distribution, and that individuals with the greatest abdominal fat loss would realize the greatest changes in breathing mechanics. METHODS All subjects underwent pulmonary function testing, hydrostatic weighting, fat distribution estimates (based on MRI scans), and graded cycle ergometry before and after a 12-week diet and exercise weight loss program. In 7 men, esophageal and gastric pressures were measured at rest and during exercise. Differences were analyzed at rest, ventilatory threshold (VTh), and peak exercise by dependent t-test and the relationship between variables was determined by regression analysis. RESULTS The subjects lost 7.4 ± 4.2 kg of body weight and 5.9 ± 3.6 kg (13 ± 8%) of fat weight (p <0.001), but fat distribution remained unchanged. At VTh, EELV was significantly increased (p <0.05), but increases at rest and peak exercise failed to reach significance. The changes in waist circumference, hip circumference, weight-to-height ratio, BMI, abdominal fat, and subcutaneous abdominal fat with weight loss were consistently and significantly correlated (p <0.05) with changes in gastric pressure at rest and during exercise. CONCLUSION These data suggest that losing fat weight in or around the abdomen has an important influence on gastric forces generated during breathing in otherwise healthy mild-to-moderately obese men. Supported by the American Lung Association.