On the face of it the basis for myth number six seems to make sense as there is evidence which supports what it is saying. It goes like this. If you exercise at a comfortable pace, a pace at which you can continue to hold a conversation, for a long period of time, you will use up more of your body’s fat reserves as this type of exercise relies on fat for fuel rather than short lived carbohydrates. Your body is said to be in a ’steady state’ during this type of exercise, one where the oxygen demands of the body are constantly met by supply. Conversely, during intermittent anaerobic high-intensity workouts, carbs are the primary source of fuel. So, the evidence kind of stacks up doesn’t it? Well, no not really because it doesn’t take into account another characteristic of the high intensity workout.
This characteristic is the tendency for the body to continue burning fat well after the initial exercise is complete. If you add this amount of fat loss to the fat loss you achieve during the exercise itself, then the overall fat loss is greater than that of the low intensity workout which may itself last as much as three times longer. This is because after the low intensity workout the body doesn’t continue to consume fuel for anywhere near as long.
The high intensity short duration workout causes the body’s fat burning metabolism to spike, kick starting it into high gear. This short term shock causes the body to work extra hard and crucially requires that calories are expended for several hours afterwords in order to recover.
It is true that the during the exercise the primary fuel source will be carbohydrate, but overall the amount of calories burned off during, and crucially, following the session will be higher than that of the more traditional low intensity workout. After having ignited the fat burning metabolism, the body continues to use up fuel even when you are resting. This is just not the case with low intensity exercise as the fat burning metabolism never gets that initial spike.
There is another benefit of following this advice too. What would you rather do, work quite hard for 15 to 20 minutes or work slightly less hard for 40 to 45 minutes? I don’t know about you, but my time is precious and if I can achieve better results in a shorter amount of time by working a bit harder, then that’s what I will do.
Also, there is the possibility that exercising for longer gives you more chance of sustaining an injury and a low intensity exercise regime does not promote muscle development. We know from some of our previous myths that having a decent amount of lean muscle fibre enables your body to be more efficient at burning off fat. So, in short, work hard with high intensity workouts for 15 to 20 minutes at a time using interval based cardio exercises and you will lose fat at a much increased rate.