The purpose of this experiment was to compare the energy expenditure and the physiological response among two groups by percent body fat(group A: 30-35% body fat, B: 35-40% body fat) to walking and running at several equivalent speeds. Subjects in group A and B followed A group(mean$pm$SD, age; 24.0$pm$0.4yrs, body fat; 32.3$pm$0.7) and B group (age; 25.2$pm$0.7yrs, body fat; 36.7$pm$0.9). The walking and running protocol consisted of treadmill speeds for five min at each of the following speeds: 5.0, 5.5, 6.0, 6.5, 7.0 km.$hr^{-1}$. The obtained data reveal in group A, the rate of oxygen consumption and energy expenditure was higher during walking compared to running ate treadmill speeds $geq$ 6.6km.$hr^{-1}$. In group 5, the rate of oxygen consumption and energy expenditure was higher during walking compared to running ate treadmill speeds $geq$ 6.8km.$hr^{-1}$. Heart rates and respiratory exchange ratio were higher at treadmill speeds $geq$5.8 in group A and $geq$5.5 in group B. these findings demonstrated that a difference of percent body fat in obese women have no large effect on energy efficiency of walking, but walking within speeds 6.5~7.0km/hr resulted in rates of energy expenditure that were as high or higher than jogging at the same speeds even though the relative stress was greater during walking.