EXERCISE CAPACITY AND ENERGY-EXPENDITURE OF MORBIDLY OBESE AND PREVIOUSLY OBESE SUBJECTS

Objective: To determine whether morbidly obese and previously obese wo men fail to lose weight after gastric bypass surgery because of reduce d energy expenditure, and whether a large, surgically induced, rapid w eight loss improves exercise capacity on a treadmill. Design: Cross-se ctional study. Participants: Four groups of 5 subjects: 1) patients st ill obese 12 months after surgery (failure); 2) patients who achieved normal weight after surgery (success); 3) obese patients who had not y et undergone surgery (preoperative); and 4) nonobese (control) subject s. Four subjects in the preoperative group were studied again at 6 mon ths postsurgery. Main outcome measures: Total daily energy expenditure (TDEE), and exercise capacity and peak oxygen consumption ((V)over do t O-2) during treadmill exercise.Results: TDEE or energy expenditure ( EE) above basal metabolic rate (when normalized for body size) was sim ilar for all groups, but the absolute energy consumption was higher in the preoperative and failure groups. Treadmill endurance time was gre ater 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 (V) over dot O-2 body weight was similar in the succes s, failure and preoperative groups, which meant that the peak (V) over dot O-2 was lower in the success group than in the preoperative and f ailure groups. Six months after surgery, peak (V) over dot O-2 had not decreased in the preoperative group. Conclusion: Failure to lose weig ht after isolated gastric bypass surgery was not because of a lower le vel of activity. Aerobic capacity was impaired 1 year, but not 6 month s, after a large weight loss. Exercise training may be appropriate to maintain absolute peak oxygen consumption.