Bruce and Mick are both right. The way to do it is combine the two. Bill Philips "Body for Life" has something he calls the 20 minute cardio solution. He suggest it three days a week. It's a chart that you use when doing cardio that takes you from a mod walk to an actually sprint during the 20 minute period. You slowly ramp up during the work out and basically tricking your body into thinking your exerting yourself more than you are and increase fat burning without the punishing effects on your joints that jogging creates.
Bruce the challenge is most overweight people 275 and above really can't reasonably go for a jog. Yet, walking alone will eventually become not enough exertion for the body and your basal metabolic rate will just attenuate itself to the activity. It's the eventual short term high intensity burst that stimlutes caloric utilization.
In the same book he also has a very cool way of doing your resistance training that basically turnd your strenght training from mostly anerobic to aerobic and allows increased fat burning by building muscle. He cuts down the rest time between sets and you basically pyramid upward for about 5 exercises of the same muscle group followed by a final drop down burn set. Awesome. Sweat more weight training then you ever have.
Whe I was competing in strong man this is how I would cut my winter weright and get reayd to go. Twelve weeks I go from a soft 275 to a rockhard 245 I've found this to the most reasonable way to do it. Though at this point in my life I prefer a see food diet and only walking my dog at a slow methodical pace so when asked I can tell Ms. Crusher, "yes honey I did exercise".