Some run for the pure enjoyment of it, some like to engage in competition, and others see it as a proven method of not looking like the Michelin Man. For many people, including me, it is a combination of these reasons. I'll confess that I'm forever pursuing more abdominal definition, which isn't easy for a beer-loving guy in his forties. While watching what I eat is important, it's the many kilometres of running each week that gives me a visible "four pack."

If you want to succeed at running long-term it's critical to love what you're doing and not just think of it as a means to an end. Realistically, however, many of us want to look good and running is one of the best calorie-burning exercises around. I can do a better job of loving it when I know it's helping eliminate some of the beer and pizza I inhaled the night before. So, what is the best way to run if you want to shed pounds? There are a few caveats such as your level of ability and preventing injury, but once you take those things into consideration the advice is simple: run as fast as you can for as long as you can.

There you go. Class dismissed.

On second though, let's bust one of the most popular myths about using aerobic exercise to burn fat.

Myth: The best way to burn fat is to keep your heart rate in the "fat burning zone"

This is true, but completely irrelevant. Yes, you do "oxidize" more body fat at moderate intensity levels and burn more carbohydrate fuel at higher intensities, but think of your energy stores as one big soup and it all comes out as a wash.

If you've ever seen a heart rate chart on a treadmill then you've read "fat-burning zone" at a moderate heart rate (about 60 percent of maximum) and "cardiovascular training zone" at a higher rate (75 percent of maximum or greater). Those charts aren't lying, but neither do they tell the full story. In a 2005 article in the European Journal of Sport Science, researchers measured fat burning oxidation rates at levels of intensity ranging from 25 percent to 85 percent of VO2peak (85% of VO2peak = 90% of max heart rate) and determined that the highest level of fat oxidation was at 65 percent intensity. Fat burning became "negligible" at intensities above 85 percent because at the highest intensities we burn mostly carbohydrates for fuel. These facts lead many to believe that exercising at a moderate intensity causes enhanced fat burning. While technically factual, it ignores the bigger picture.

Ironically, fat loss is not about using fat for fueling activity; it is calories in vs. calories out, which needs to be viewed from the perspective of what is called the 24-hour energy balance. If your energy balance is negative (more calories burned than consumed) weight is lost; if your energy balance is positive weight is gained. Yes, you may use more body fat for fuel while exercising at a moderate intensity, but in the grand scheme of the 24-hour energy balance equation this means nothing. If you exercise to create an overall negative energy balance you are going to burn those fat stores at some point in the day, whether you happen to be eating, sleeping, working or have wild and crazy trapeze sex (Giggity). The fact that the ratio of fat burned during moderate exercise was higher for fat than carbohydrates doesn't matter.

Having time to exercise is an important issue for many people. If you have 40 minutes in your schedule and want to maximize calories burned then pick the fastest pace you can handle for that duration of time. If you've ample time this equation changes to a balancing act of finding a challenging yet sustainable level of intensity – Bircher's aforementioned research found the most total calories were burned at a 75 percent intensity level. And if fat loss is your goal, then it is total calories that you are worried about. A 1998 article in the Journal of the American College of Clinical Nutrition found that sustained high-intensity exercise was far better at decreasing body-fat content than exercising at lower intensities.

It's important to note that metabolism increases on a sliding scale the higher the intensity, so you burn more calories running five kilometres than walking or slow jogging those same five km (and in less time). There are other great reasons to run at a higher intensity: It improves your overall cardiovascular fitness level making you more capable in other sports and it is better at boosting HDL (good) cholesterol.

To conclude, the best pace to run at is the one you like the most – the pace that keeps you lacing up those shoes. Just don't be afraid to incrementally push your limits if you want to burn more calories and therefore lose more fat.

James S. Fell is a Certified Strength and Conditioning Specialist and a middle-aged family man with a desk job and not much free time, yet he's able to keep in shape because he loves exercise and doesn't mind eating healthy. He is the author of Body for Wife: The Family Guy's Guide to Getting in Shape. His column for That's Fit.ca focuses on weightlifting, running and exercise motivation.