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Get Out Of The Fat-Burning Zone

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Cardio is hard-io but oh so important. And not for the reasons you might think. In fact, when most people think about cardio they think weight loss but it's time to change that mindset -- weight loss is a nice side effect but it's not the main reason for you to break a sweat.

Now there are a thousand things that I'd love to tell you about cardio, which means this could take hours and hours to read but I thought I would start with a hot topic -- high-intensity interval training (HIIT). You've likely heard the term and if you've ever tuned into an episode of the Biggest Loser (or any other weight-loss reality show), chances are you saw them doing some form of HIIT. So let's take a closer look at what exactly HIIT is and why or why not you might want to add it into your fitness regime.

About a decade or so ago, you may remember many fitness professionals and even doctors prescribing lower intensity activity to maximize fat loss. Many fit people lowered the intensity of their workouts fearful that they were not burning fat. Unfortunately, they were misled but many people still believe that low-intensity activity is the best way to maximize fat loss. The reality is that the activity that expends the most amount of calories will lead to the most amount of fat burned.

Physiologically it's true that during lower intensity activity you will burn a higher percentage of fat and during higher intensity activity you will burn a higher percentage of carbohydrates or sugars. But the important point to note is that when you exercise at a lower intensity you are definitely expending fewer calories. The selective use of fat as a fuel, specifically at lower intensities, does not translate into greater fat loss, regardless of how tempting it is to draw this conclusion. The more important focus with regard to calories expended, is not the percentage of energy coming from fat, but rather the total volume of fat used and the total number of calories expended. Confused? Let's look at the math.

At 60 per cent max heart rate (easier intensity)
Approximately 50% of calories come from fat (50% from sugars)
Approximately 8 kcal/min are expended
60 minutes x 8 kcal/min = 480 total calories
50% x 480 kcal = 240 fat calories

At 80 per cent max heart rate (more vigorous intensity)
Approximately 40% of calories come from fat (60% from sugars)
Approximately 11 kcal/min are expended
60 minutes x 11 kcal/min = 640 total calories
40% x 640 kcal = 264 fat calories

From these figures, you can see how we've been misled. If you were to examine only the first line, the percentage of fat being burned as fuel, you would definitely prescribe lower intensity activity. However, if you examine the whole picture, it is clear that higher intensity activity definitely expends more calories and also more fat.

If I have not convinced you yet, consider this -- the highest percentage of fat that you burn during any activity is during rest! At rest, you are using approximately 50 per cent fat as your fuel -- that is the highest percentage of fat you can burn -- you are never burning 100 per cent fat. That's right, just sitting here reading this you are likely burning the highest percentage of fat you could possibly burn. That is because your body can only store a limited supply of carbohydrates (sugars) and so during rest, the demand on your body is low and your body wants to spare your precious sugar stores. Since you have a virtually unlimited supply of fat stores, your body would rather burn fat during rest.

But remember that although you are burning a higher percentage of fat at rest, you are expending very few calories (approximately 1kcal/min) so overall you are not burning a lot of fat. If type of fuel utilized was the critical factor for fat loss, then we would be prescribing more rest because this is when we burn the highest percentage of fat as fuel. But it is a higher percentage of a lower number of calories. So, of course, we know it is ridiculous to even consider rest or sleep as a high-fat burning activity.

But here is the most important thing...

It's true that everyone can benefit from incorporating high-intensity training into their program once they have completed the initial level of base conditioning. The recommended fitness prescription is one that includes all intensity training zones. That is, sometimes you go easy and slower and other times you go hard and fast. This will ensure you train all of your energy systems and minimize over-training.

As a reminder, don't start with high-intensity exercise. Complete a month or two of easier, base conditioning first. And NOT ALL of your workouts should be at a high intensity. Mixing it up is always the best prescription.

Share with us, what's your favourite type of cardio training?

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