In researching the optimal way in which to lose body fat, I've found a couple of important facts. First of all, it's the total calories you burn through exercise, or through a reduction in intake, that are important, not the kind of calories. In the past, many have suggested that by exercising aerobically at low-intensity, one could enter a "fat-burning zone", while exercising at a more intense rate would put a person out of the fat-burning zone, and into the carb-burning zone. Research has not proven this to be true.
Simply put, less calories in and more calories out is what creates fat loss.
The argument persists between low to moderate intensity workouts versus high intensity workouts. Which is better? The answer is, both can be productive at reducing fat. There is a simple equation that illustrates what I'm trying to say, and that is, the higher intensity exercise a person can safely maintain for as long as the person can maintain it will burn the most calories. So if you're time is limited, a high-intensity cardio workout for 20 minutes, may be the equivalent of a moderately intense 30-40 minute workout--at least as far a burning calories goes.
An excellent article on the subject can be found here: http://www.mens-total-fitness.com/cardio.html
The bottom line is, to lose fat effectively, you need to exercise at a pace that you can continue doing 5-6 days a week for the rest of your life. Increasing duration or intensity will speed up the overall fat burned during any one particular session of exercise. Once fat-loss goals have been reached, you can generally back off a bit on the total amount of exercise.
Key also in this is diet. My best advice is this: Avoid fast foods, eat desserts sparingly, get enough protein in your diet in a form other than red meat, eat a lot of veggies. Also, choose good snacks to eat throughout the day, and that doesn't mean Oreos or Twinkies!
Good luck on making your fitness goals in 2011! I'm right there with ya.