F19B FREE COMMUNICATION/SLIDE EXERCISE AND OBESITY
The purpose of this study was to investigate the role exercise intensity plays in reducing body weight and/or percent body fat in overweight women (Age: 33.8 ± 8.2 yr; HT: 165.7 ± 6.8 cm; WT:88.0 ± 21.4 kg; BMI: 31.8 ± 6.6 kg/m2; % body fat: 42.9 ± 6.8%). Subjects were randomized to either a high intensity interval training group (IT: 2 minutes at 95% of VO2max alternating with 3 minutes of 25% of VO2max) or a lower intensity steady state training group (ST: 50% of VO2max). T-tests showed no pre-existing differences between the two groups. Oxygen consumption and R-values were measured so that each group expended 300 kcal per exercise session. Duration of exercise varied to allow for equal caloric expenditure. Body composition was measured using hydrostatic weighing, bioelectrical impedance analysis, and dual energy X-ray absorptiometry (DEXA). Currently, all body composition measurements refer to those taken with DEXA. Resting metabolic rate (RMR) was measured via indirect calorimetry at least 48 hours after the subject's last exercise bout. The fitness level of the IT was found to increase by 13.1% (25.2 ± 4.2 to 28.5 ± 5.1 ml/kg/min; p < 0.03) whereas no change was found in the fitness of the ST (28.7 ± 3.3 to 27.2 ± 3.7 ml/kg/min; NS). Percent body fat showed a decreasing trend in the IT (45 ± 8.4 to 42.8 ± 7.2%; p = 0.08), but no change was found in the ST (40.4 ± 3.4 to 40.9 ± 3%; NS). Neither group showed a change in RMR from pretest to posttest; however, the interval training group showed an acute 5.4% increase in RMR 24 hours post-exercise (1671 ± 406 to 1761 ± 412 kcal/day; p < 0.04). This may explain, in part, the trend for a 4.8% decrease in body fat percentage. These findings show that even if caloric expenditure during exercise is equal, higher intensity exercise may furher aid weight loss due to an acute increase in energy expenditure up to 24 hrs following exercise.