Effect of weight loss on operational lung volumes and oxygen cost of breathing in obese women

BACKGROUND: The effect of moderate weight loss on operational lung volumes during exercise and the oxygen (O(2)) cost of breathing are unknown in obese women but could have important implications regarding exercise endurance. METHODS: In twenty-nine obese women (33 ± 8yr, 97 ± 14kg, BMI: 36 ± 4, body fat: 45.6 ± 4.5%; means ± SD), body composition, fat distribution (by MRI), pulmonary function, operational lung volumes during exercise, and the O(2) cost of breathing during eucapnic voluntary hyperpnea ( [Formula: see text] vs. [Formula: see text] slope) were studied before and after a 12-week diet and resistance exercise weight loss program. RESULTS: Participants lost 7.5 ± 3.1kg or ≈8% of body weight (p < 0.001), but fat distribution remained unchanged. After weight loss, lung volume subdivisions at rest were increased (p < 0.05) and were moderately associated (p < 0.05) with changes in weight. End-expiratory lung volume (%Total Lung Capacity) increased at rest and during constant load exercise (p < 0.05). O(2) cost of breathing was reduced by 16% (2.52 ± 1.02 to 2.11 ± 0.72ml/L; P=0.003). As a result, O(2) uptake of the respiratory muscles [Formula: see text] , estimated as the product of O(2) cost of breathing and exercise [Formula: see text] during cycling at 60W, was significantly reduced by 27 ± 31ml (P<0.001), accounting for 46% of the reduction in total body [Formula: see text] during cycling at 60W. CONCLUSIONS: Moderate weight loss yields important improvements in respiratory function at rest and during submaximal exercise in otherwise healthy obese women. These changes in breathing load could have positive effects on the exercise endurance and adherence to physical activity.