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

BACKGROUND

The effects of moderate weight loss on operational lung volumes during exercise and the oxygen (O2) cost of breathing are unknown in obese women but could have important implications regarding exercise endurance.

METHODS

In 29 obese women (33±8 years, 97±14 kg, body mass index: 36±4 kg m(-2), body fat: 45.6±4.5%; means±s.d.), body composition, fat distribution (by magnetic resonance imaging), pulmonary function, operational lung volumes during exercise and the O2 cost of breathing during eucapnic voluntary hyperpnea (([Vdot ]O2) vs ([Vdot ]E) slope) were studied before and after a 12-week diet and resistance exercise weight loss program.

RESULTS

Participants lost 7.5±3.1 kg 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 (percentage of total lung capacity) increased at rest and during constant load exercise (P<0.05). O2 cost of breathing was reduced by 16% (2.52±1.02-2.11±0.72 ml l(-1); P=0.003). As a result, O2 uptake of the respiratory muscles ([Vdot ]O2Resp), estimated as the product of O2 cost of breathing and exercise ([Vdot ]E) during cycling at 60 W, was significantly reduced by 27±31 ml (P<0.001), accounting for 46% of the reduction in total body ([Vdot ]O2) during cycling at 60 W.

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.