Picking up on last week’s post on calories burned during exercise, we’ll address the two main problems with how calories are conventionally counted today.  As a reminder, these two problems were the following:


  1. Most methods are gross estimations based off averages

  2. These methods (inadvertently) mislead you into thinking the calories you burned during your workout is all that matters

Taking a quick look at the first problem, how do we get an accurate measurement of calories burned during exercise?  One way is we use the respiratory quotient, or RQ for short.  RQ is the amount of carbon dioxide exhaled versus the amount of oxygen inhaled.  This is very accurate and unique to you, the individual, rather than based off averages that have very little to do with you and your uniqueness.  

That being said, unless you're gonna invest the time into doing this test, it's of little consequence to you.  What's more important to know is that most measurement approaches are inaccurate and focusing on calories burned during exercise is a poor use of time.  So problem #1 solved!...mostly

Looking at the second issue, what else matters besides the amount of calories burned during your workout?  For one, the intensity of the exercise.  Low intensity exercise (walking, jogging) uses mostly stored body fat for energy while high intensity exercise uses mostly stored muscle glycogen (sugar) for energy.  We know this based off exercise science, cell metabolism and the RQ.  Burning fat for energy, sounds like what we want right?

If the RQ is at .7 or below, we can say that 100% of the energy expenditure is coming from body fat.  Anything above that, and we’re using some amount of stored muscle glycogen.  An RQ of .85 corresponds to about 50% fat and 50% glycogen for energy, respectively, while an RQ of .95 corresponds to about 20% fat and 80% glycogen, respectively.  

The most interesting part of all this is that with low intensity exercise, you might be burning a higher percentage of fat during your workout, but won’t be burning much at all during your recovery.  On the other end of the spectrum is high intensity exercise, which will use mostly muscle glycogen for energy during the workout, but because of how intense of a stimulus it is, your body will be forced to adapt and recover.  During this post-exercise phase (lasting anywhere from hours to days) you’ll be in a “low intensity” state where your body is forced to use body fat for energy.  What does this mean?  It means you’ll burn far more fat from a short high intensity bout than much longer stints of low intensity exercise.  So problem #2 solved!

So what are we saying?  When you do high intensity exercise, you’ll burn a good amount of calories during your workout, but afterwards is where the real magic is.  That’s where you’ll burn a ton of body fat.  So increase the intensity people!  Your workout can be as short as 10 or 15 minutes, rather than an hour or two.  


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