Consider if you run three miles six days a week. That's about 350 calories a day assuming you are an average slug runner. Six days a week it's 2100 calories. In a month that's 8400 calories. In ten months that's 84,000 calories. Not even counting the calories from a burning metabolism the running has created. Anyone that has started a serious running program can tell you the weight loss is more than the sum of the calories apparently used during the run. In ten months you will burn off approximately 24 pounds of fat. I never said you can eat like a slob and work out. It's all a cohesive holistic health endeavor of weights and cardio for most people trying to get lean. Many non runners are shocked at the weight loss in 6 weeks that a running program helped achieve.
It's more of causation not being correlation. Most avid runners I know try to lead a healthy lifestyle hence they will watch their diet closely. So yes, if you take up running and stick with it, you will get leaner, but NOT because of the calorie burn for 3 miles. That is insignificant.
I know this all too well. When I gear up my cycling in the spring for longer races, my bodyweight does not decrease even one ounce until I start hitting 7-10 hours a week. That's burning off approximately 900 calories an hour x 7 = 6300 extra calories a week! Your body gets very efficient at calorie burning as you train.
Most fat people would be better off just walking 20 min a day and watching what they eat. And lifting weights- to maintain muscle mass while dieting.
