The purpose of this study was to examine the cardiorespiratory responses to weight reduction resulting from physical exercise in 14 obese women, aged 36 to 67 years (mean body mass index [BMI], 32.4 ± 1.4 kg/m 2). The patients were instructed to exercise at approximately 60% of the maximum oxygen uptake (VO 2 max) for a total of 2 hours every day for approximately 3 months. To evaluate physical strength, a graded cycling exercise test that monitored gas exchange, ventilation, and heart rate was performed both before and after the study. The following results were obtained: (1) After the exercise period, BMI and percentage of body fat decreased by 10.3% and 17.9%, respectively ( P < 0.001), although lean body mass did not change significantly; (2) VO 2 max and maximum heart rate did not change significantly, while peak ventilation equivalent (VE peak), maximum metabolic equivalent (METS max), and maximum load (LOAD max) increased by 12.3%, 13.6%, and 11.4%, respectively (VE peak, P < 0.05; METS max and LOAD max, P < 0.001); (3) maximum oxygen uptake per body weight increased by 15.3% ( P < 0.001). These results suggest that weight reduction due to exercise improves cardiorespiratory function in middle-aged obese women.