IMPROVED GAS-EXCHANGE DURING EXERCISE AFTER WEIGHT-LOSS IN MORBID-OBESITY

The aim of this study was to determine the effect of weight loss induc ed by 6 weeks very-low-calorie-diet (VLCD) and behavioural interventio n on pulmonary gas exchange during exercise in non-smoking morbid obes e (BMI>40 kg/m(2)) otherwise healthy patients. Seven obese patients un derwent a maximal bicycle ergometer test with continuous analysis of e xpired air and arterial blood sampling before and after a mean weight loss of 18% (25.7 kg, range: 10-50 kg). Body mass index (BMI) decrease d with weight loss from 46.6 (6.3) kg/m(2) to 38.0 (4.7) kg/m(2) (P<0. 01). Oxygen consumption (VO2) at low and submaximal exercise levels de creased after weight reduction, but the change was not statistically s ignificant. The peak oxygen consumption related to body weight (VO2/kg ) increased 22% from the initial 16.2 (3.6) ml/min/kg to 19.8 (3.1) ml /min/kg (P<0.05). Decrease in VCO2 was significant at submaximal exerc ise level. Ventilatory equivalent for CO2 increased significantly afte r weight reduction (P<0.05). Standing up and light exercise resulted i n a significant increase in the mean arterial oxygen tension (PaO2) (P <0.05) and a significant decrease in the mean alveolar-arterial differ ence P(A-a)O-2 (P<0.05) when compared to supine values. The mean incre ase in PaO2 with weight loss was not significant. The peak P(A-a)O-2 d ecreased significantly after weight reduction. In conclusion, weight r eduction induced by VLCD and behavioural intervention without exercise therapy can improve gas exchange during exercise in morbid obesity. I ncreased wasted ventilation, and a tendency to alveolar hyperventilati on, after weight loss may reflect a delay in the adaptation of regulat ion of breathing to rapid weight loss.