Exercising to burn calories...but are you burning fat?

Learn how you can exercise to not just burn calories but fat as well.

I hope through our discussions that people who are reading this are now actually exercising.  Previously we went over how to get back into an exercise routine and how our body responds to exercise as well as injury.  We also reviewed some of our decision making processes when we feel some muscle pain (see previous blogs to catch up). 

When it comes to exercising, particularly for those who don't already have a routine, the motivation to lose weight is probably the biggest draw for exercise novices to begin a routine. For those of you who do exercise in an attempt to lose weight I have good news.  When combined with a healthy diet, exercise is an effective way to lose weight.  Interestingly, there is some debate over what type of exercises to perform in order to achieve optimum weight loss.

One example might be what I call the "go as hard as you can for as long as you can" approach.  It's simple and straightforward and it does make intuitive sense.  Burn as many calories as you can would be another way to say it.  Does this approach work?  Absolutely, and this is the type of approach that you might see at a "boot camp" workout.  The one caveat with this type of approach is that it tends to lead to a higher amount of musculo-skeletal injuries and a lot of soreness.  It also may add lean muscle to your body - which you may or may not want.

There is another alternative that for many of us may be a little less severe, and potentially more effective.  What if we could exercise in a specific way that allows our body to preferentially burn more fat.  It turns out that we can, but you need to understand your body better before going any further. 

Our body has three energy systems available to it.  Although they all work together, virtually simultaneously, each one is distinct and unique.  The first energy system is the immiediate energy system.  This gives us the immediate energy to spring up from a chair or lift a heavy box instantly.  When you are at rest, your body places energy right into the working parts of the muslce so that the muscle can work instantly on command.  I like to call this "loading the gun".  It's like putting bullets into the chamber of a gun so that when you have to "shoot", or turn on your muscles, they are ready to go.  The problem with this system is that it doesn't work very long, as we tend to "run out of ammo" pretty quick.  Its effectiveness is measured in seconds, so it can't supply very much energy after that.

We then have our short-term energy system, which uses the same energy as the immediate system except that it needs to be "loaded" into the muscle before working.  The muslce has stores of energy within each cell but it has to transport it to the exact spot that it is needed, which takes a little bit of time - a few seconds.  This system's effectiveness is measured in minutes, so it can't be the main provider of energy for long periods of time.   

The final system is what we call the long-term energy system.  This system needs time to start up but theoretically it can supply the body with energy indefenitely - as in forever.  The reason why it's theoretical is that other systems of the body will break down before you actually run out of energy, so that we never really get to put that statement to the test.  I don't think anyone would want to either.  I love exercise but who wants to literaly exercise forever - not me.

The long-term energy system is what we are interested in.  What makes it so great for our purposes?  Here's the big difference.  The long-term system uses oxygen.  The other two do not.  Why is that important?  Because fat can not be utilized as energy without oxygen.  Your body will readily burn fat as energy when there is adequate oxygen available.  Fat is by far the most abundant and energy dense of all fuel available to the body.

The first two energy systems work instantly in the absence of oxygen, as a bridge to get to the long-term system that has to wait for the presence of oxygen.  Once present, the long-term system will take over the bulk of the work, as long as their is adequate oxygen.

How can we use this information to our advantage?  By making sure we exercise at an intensity that keeps our long-term energy system working as the primary system.  When our intensity increases too fast, we need more oxygen, and we start to breath harder to get more.  That is when we get in a state of oxygen debt, which means that the short-term energy system has to come to the forefront to meet the demands of the situation because the long-term system doesn't have enough oxygen to meet the demands.  We then burn much more carbohydrates as opposed to fat.

Now that you understand how the body's energy system works it makes perfect sense that an ideal fat burning workout would start slowly, go for a long time, and have an intensity that stayed relatively constant.  A good way to know if your intensity is too much is to talk out loud.  If you can't finish a normal sentence without stopping to breathe in the middle of the sentence then the intensity is too high.  Make that long-term system work and you will burn fat.

These concepts are a little complicated so please don't hesitate to ask questions or comments, or if you have a question about your particular workout regimen feel free to ask a question.

Yours in Health,

Chris Ostling PT, DPT


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