Any time I head to a crowded gym the one thing that really grates me is peering over at the ‘cardio area’ and seeing hordes of individuals completing low intensity cardio exercise focusing on the ‘fat burning zone’.
When it comes to the quickest way to lose belly fat, the fat burning zone is a myth. There… I’ve got that off my chest.
Despite this… countless trainers are still prescribing boring low intensity cardio exercise… and most cardio equipment continues to be plastered with stickers representing the ‘target’ zone that is ‘ideal’ for burning fat.
As I said, it really grates me. Although I can understand the reason for the confusion.
When we exercise we draw energy from two sources. Fat stores and glycogen – which is carbohydrates broken down and stored in the muscles and liver.
Now it is technically true that exercising at a lower intensity (say from 55-65% of your maximum heart rate) will use a higher PERCENTAGE of fat calories as fuel when compared to carbohydrates or glycogen.
For example – at an intensity of 50% of your maximum heart rate – your energy ratio would be around 60% fat and 40% carbs (glycogen).
Bump it up to 75% intensity and it flips. 35% fat and 65% carbs.
So why over extend yourself when you exercise then? A walk around the block is probably the quickest way to lose belly fat right?
Listen carefully… I mentioned above that this was a percentage of the total amount of fuel used. At lower intensities the amount of fuel used (or calories burned) is pretty low.
The real effectiveness of a workout is in the total volume of calories burned.
Have a look at the table below that compares medium intensity exercise against a higher intensity performance.
The table demonstrates that the percentage of fat calories burned is much higher in the medium 30 minute exercise bout. However, the total fat calories and overall calories burned are much higher in the high intensity effort.
Source: The 24/5 Complete Personal Training Manual, 24 Hour Fitness, 2000
Hopefully this makes it clear that higher intensity workouts are substantially more efficient and will help you burn more calories in less time… and more of your unwanted belly fat in the process.
OK, has that satisfied you enough to put away the slow boring cardio? No?
There is one other key reason why low intensity cardio is less efficient as a fat burning approach…. No Afterburn?
No Afterburn? What does that mean? Well basically that there is no prolonged metabolic benefit. Once you have finished your exercise… you receive virtually no ongoing elevation of your metabolism.
Compare this with higher intensity exercise where you can elevate your metabolism for up to 2 days after a really intense workout. This means that your body continues to burn calories at this elevated rate as your body recovers from your tough workout. So not only are you burning more calories during the exercise period… you are using a bunch more long after the exercise session as finished.
Hopefully that has convinced you that low intensity exercise is NOT the most efficient approach when it comes to losing excess belly fat.