Exercise capacity and energy expenditure of morbidly obese and previously obese subjects.

Objective: To determine whether morbidly obese and previously obese women fail to lose weight after gastric bypass surgery because of reduced energy expenditure, and whether a large, surgically induced, rapid weight loss improves exercise capacity on a treadmill.

Design: Cross-sectional study.

Participants: Four groups of 5 subjects: 1) patients still obese 12 months after surgery (failure); 2) patients who achieved normal weight after surgery (success); 3) obese patients who had not yet undergone surgery (preoperative); and 4) nonobese (control) subjects. Four subjects in the preoperative group were studied again at 6 months postsurgery.

Main Outcome Measures: Total daily energy expenditure (TDEE), and exercise capacity and peak oxygen consumption (VO2) during treadmill exercise.

Results: TDEE or energy expenditure (EE) above basal metabolic rate (when normalized for body size) was similar for all groups, but the absolute energy consumption was higher in the preoperative and failure groups. Treadmill endurance time was greater in the success than the failure and preoperative groups, and the endurance times of these 3 groups were less than those of the nonobese subjects. Peak VO2 body weight was similar in the success, failure and preoperative groups, which meant that the peak VO2 was lower in the success group than in the preoperative and failure groups. Six months after surgery, peak VO2 had not decreased in the preoperative group.

Conclusion: Failure to lose weight after isolated gastric bypass surgery was not because of a lower level of activity. Aerobic capacity was impaired 1 year, but not 6 months, after a large weight loss. Exercise training may be appropriate to maintain absolute peak oxygen consumption.