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Proportion vs Volume of Fat Burned

     There are a lot of misconceptions in the world of exercising for fat loss. There are thousands of studies that will all prove the next one in line wrong with facts and hypotheses based on solid case studies. This week alone I’ve been approached with the same topic on a couple different occasions, so I figured I’d shed some light on one of these misconceptions.


     “Ive heard that low intensity training is the most efficient means for fat loss, so why are we constantly training at a high intensity to burn unwanted fat at ATS?”


     In order to answer this question fully, we first need to delve into where this theory came from, and why it doesn’t work like it claims to.


     There are many fat loss programs out there that were designed by trainers and fitness professionals around the world that base their fat loss programs around the theory that a greater amount of fat is most efficiently burned through low intensity aerobic exercise. However there is one glaring problem with this theory; PROPORTION of fat burned is much different then VOLUME of fat burned.


     First, one must understand that carbohydrates are the leading resource burned for useable energy in our bodies. Glucose (the most simple form of a carbohydrate) is the main energy source for the creation of ATP which, in short is the fuel that runs our muscles during exercise. Fat falls in second place as the body’s next resource for useable energy. Keeping this article on topic; when you are sitting down relaxing, your body is deriving the majority of its energy requirements from fat in your body. Unfortunately, we all know that sitting and relaxing doesn’t do much in the way of eliminating unwanted body fat. Why? While sitting there, the proportion of fat being burned is very high in terms of where your body is deriving its energy sources from(fats vs carbs vs protein), but the total volume of fat being burned in terms of calories expended is very low.


     When exercise intensity increases, the proportion of energy burned from fat is decreased and the proportion of energy burned from carbohydrates is increased. The higher the intensity, the higher the proportion of carbohydrates will be burned. What I just said, seems to support the theory of low intensity training being the more effective form of fat loss, right? Wrong. This is where we look at the difference between proportion and volume.


     The greater the energy expenditure, the greater amount of total calories burned. In other words, during high intensity training the total number of calories burned per unit of time will be much higher than that of the total number of calories burned during low intensity training. This means that the volume, or the total number of calories burned from fat, will be much higher during high intensity training, despite the lower proportion of fat being burned during the high intensity training.

This is all rather confusing, so lets try to put this into a simple scenario:


You run on the treadmill at a low intensity pace (<70% of VO2 max) for 30 min and burn 200 calories. 75% (170 calories) of which were burned from fat.


You complete a much higher intensity workout (FITCAMP class) for the same 30 minutes and burn 400 calories. 60% (240 calories) of which was burned from fat.


     Now you can see during the low intensity workout the proportion of fat burned (75%) is greater then the proportion of fat burned during the high intensity workout (60%). That doesn’t mean much because the total calories burned were greater during the high intensity workout (170 vs 240) so the volume (or total calories burned) of fat burned is much greater during the high intensity workout. You would have burned 200 more total calories during the high intensity workout than you would have during the low intensity workout in the same time frame and you would have also burned 70 more calories from fat during the high intensity workout, versus the low intensity workout during the same time frame.


     I hope this helped shed some light and show you why we, at ATS are constantly harping on you about high intensity training.


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