On the cardio, a fast walk will just take longer to get the pulse up, as opposed to a run or jog. On the fat loss, I think it's simple physics here... To move a 175-lb mass (x) distance =
calories burned. Only difference is speed in which those calories will be burned, which = time needed to move the mass the same distance. There are of course other small factors, such as size of steps taken, and the amount of energy lost in shoe flexion, etc... So if you travel the same distance whether running, jogging, or walking, you should burn about the same amount of calories; subtracting a few calories for saving energy lost in pounding/flexing of shoes during a jog.
Charles