Which burns more calories, walking or running?

Every weekday, a CNNHealth expert doctor answers a viewer question. On Friday, it's Dr. Melina Jampolis, a physician nutrition specialist.

Asked by Michael from Galesburg, Illinois:
I have read and heard from other people that running and walking a mile burns the same number of calories. I have compared the two on a treadmill and the difference is astounding! Walking = 92, running = 158. I understand that treadmills don't show an accurate count of calories burned, but these numbers are so different. Is this true?

Expert answer:
Hi Michael!
I'm not sure where you heard that running and walking one mile burns the same number of calories, but as you found out with your experiment, this statement is not correct.
Distance itself does not really determine total calories burned. How long you exercise, how fast/hard you exercise, how much you weigh, and your fitness level are the major determinants of calories burned.
According to the website www.caloriesperhour.com, a 200 pound man would burn 113 calories walking 1 mile at a pace of 4 miles per hour (total exercise duration = 15 minutes).
The same man would burn 151 calories running a mile at a pace of 6 miles per hour (total exercise duration = 10 minutes).
And if you were strolling for a mile at a pace of 2 miles per hour, you would burn 113 calories but it would take you twice as long (total exercise duration = 30 minutes).
This may be where the confusion takes place. You burn fewer calories exercising at a lower intensity, but if you exercise for a longer period of time, in some cases, as with walking at 2 miles per hour versus 4 miles per hour, you may burn the same total number of calories.
Exercising at a higher intensity burns more calories per minute, which is much more relevant than distance. In addition, if you weigh more, you burn more calories doing the same activity (this is just something to keep in mind. I'm not suggesting that you gain weight to increase the number of calories that you burn!).
Also, if you are more fit, you actually burn fewer calories doing the same activity, but the good news is that you burn more calories from fat when you are fit.
The bottom line is that more intense exercise, like running, is a more time efficient workout. However, many people, including myself, are not able to run because of injury or arthritis. In this case, exercise as intensely as you can, but realize that you will have to exercise for a longer period of time to burn the same number of calories.
This is why the physical activity recommendations for adults are either 150 minutes of moderate aerobic activity (brisk walking) per week or 75 minutes of vigorous (running or jogging) physical activity per week in addition to strength training.
You can also try walking on an incline (or hills) to increase calorie burn or alternating running and walking (interval training), which is great for people just starting a more intense exercise program or looking to improve their overall fitness level.