Here’s an interesting article talking about the difference in the workout/calorie burn for walking versus running. Basically, common sense is right: running burns more calories than walking if both are done over the same distance. The author looked at comparing the net calorie burn of running versus walking. Net calorie burn is the total calorie burn minus the resting metabolic calories that your body would have burned during the time of the workout even if you hadn’t been working out at all The relative net calorie burn of running a 9:30 mile is approximately the same as walking a 19:00 mile.
However, the author notes that walking should not be discounted as a good source of exercise—especially if the walking is done at a rapid pace. He states that at fast paces, walking is actually harder than running. This is because the body is really not designed to walk quickly. Moving quickly is what running is for! So trying to force your body to walk at a very fast pace actually increases heart rate, oxygen consumption, and calorie burn.
So yay for fast walking! I like walking better than running for exercise anyway, ‘cause I can easily walk at 4.3 mph or faster for upwards of four hours, but make me run at a reasonable speed for about an hour and I’m dead.