No, he's wrong. On the face of it, you might figure that when covering the same distance - in this case, a mile - you would burn the same number of calories, because while walking is less strenuous, it takes longer for a walker to cover the distance.
But just think about the difference: when you walk, you stride at whatever pace you choose. You move your legs and probably swing your arms, but that's about it. Running requires a lot more effort - you're actually jumping from one foot to the other as you propel yourself forward, and your center of gravity goes up and down as you take off and land. As a rule, running burns 50 percent more calories than walking over any given distance, even though running takes less time.
If you're trying to lose weight, you may have been subtracting the calories burned while running (or walking) from your daily intake. If so, you're probably wondering why you're not losing as fast as the numbers indicate you should be. What most people don't accurately assess are the net calories burned while exercising: of the, say, 200 calories you may burn during your run, you have to subtract the number you would be burning anyway, if you were at home lounging on your couch. The number to use when adding up calories burned through exercise is the net calorie burn (NCB). To figure out your net calorie burn per mile for running, multiply your weight (in pounds) by .63; for walking multiply by .30.
The great advantage of running is its intensity. It promotes fitness quickly and efficiently and burns more calories than many other activities. Because of its intensity, running releases endorphins in many people, creating the "runner's high" we often hear about. The runner's high - like aerobic exercise highs in general - is a good antidepressant.
On the downside, the chance of injury with running is greater than for most other aerobic activities. Running traumatizes the body, especially joints in the legs, knees, and back, as well as the kidneys. You can minimize this possibility by taking several precautions. Never run on concrete. If possible, run on cinder tracks or dirt paths. Asphalt is not as bad as concrete but not as good as dirt. Always wear well-made running shoes designed to minimize shock to the joints, and get a new pair whenever your present ones start to wear out. Women should wear athletic bras or other breast supports. Warm up before you start a run, not by stretching but by running in slow motion. Here's where you can read more about the pros and cons of running.
Walking may not burn as many calories as running, but it offers the great advantage of being a practical substitute to driving for short trips, since you can do it in street clothes and you don't typically arrive in need of a shower. Further, it requires no skill or practice. Everyone knows how to do it, and the only equipment you need is a good pair of shoes. You can walk outdoors or indoors (in shopping malls, for example). It is the safest exercise option of all, with the least chance of injury.
The main problem with walking as a principal aerobic activity is that you can easily fail to do it strenuously enough to get the conditioning benefits of exercise. Aerobic walking cannot be casual or intermittent, and it takes a little more time than the other options. You should be able to walk about three miles in forty-five minutes.
Andrew Weil, M.D.