|Calories expended per mile are pretty much the same however fast you run.|
Faster runners merely cover the distance quicker!
Data from Harvard Medical School
horizontal axis is speed in mph, vertical axis is calories used
A good question.
I took a reputable data source (Harvard Medical School), and plotted out the data on the chart above.
I used the dataset for the 185lb person, because that is the closest to what I weigh (actually I weigh more like 200 lbs!)
The first three data points are for walking at three increasing speeds, and the rest are for running.
Running uses about 1.5 times as many calories as walking for the same distance covered - no doubt due to a less efficient action of movement. Running includes having no foot on the ground for a short while, while walking basically pivots from one foot to the other, So running has an element of a small "jump" on each step.
Anyway, the set of three "walking" data points give a pretty flat line for calories used per mile.
Walking faster has no effect, other than to cover the miles more quickly.
So a 5 mile walk uses a set amount of calories however fast you walk.
The rest of the data points are for running.
Again, it makes little difference how fast you run - running at 5 mph and 10 mph use pretty much the same amount of calories per mile - more than walking, but the same as any other running speed.
Therefore, it is safe to conclude that for weight loss, the speed at which you run doesn't matter much - it is the distance that you cover that counts!