"Runner's World: Why did you do this study?This was my experience. I didn't lose the extra 15 pounds I was carrying around until I fixed my diet. No amount or frequency of running or other exercise made a meaningful difference.
"Mary Kennedy: I got the same question so often from people in marathon-training groups: 'Why aren't I losing weight?' Usually I'd give the standard response: 'You must be eating too much.' It was also possible that people weren't moving as much as normal after their workouts–they were 'compensating' for their workouts–so maybe their calorie output didn't actually increase. Eventually I realized, we don't really know the answer, and there's no good data to work from. So I thought we should devise this simple study to begin the data collection.
"RW: Did the results surprise you?
"MK: I wouldn't say there were any big surprises. More women tended to be weight gainers. I think I might have guessed that, though the reasons aren't clear.
"Also the subjects' 'eating habits' appeared to be very important. The ones who were very diligent about what they ate were less likely to gain weight. That's not a big surprise either...."
Running is great for you, and a terrific complement to the sort of healthy diet I advocate here, and it apparently has many other health benefits. Plus it's a heck of a lot of fun, IMHO.
But it's not a reliable way to lose weight.