Here is a small section from Dr. Wayne Westcott’s article about the myth of the “fat burning zone.” Full article can be found at –http://www.healthy.net/Health/Essay/What_Is_The_Fat_Burning_Zone/733
The following example is taken from the exercise physiology lab at the University of Wisconsin, LaCrosse. A 160-pound male walks for 30 minutes at a pace of 3.5 miles per hour. At this pace his energy is supplied 40 percent from fat sources and 60 percent from carbohydrate sources. On another day the same subject runs for 30 minutes at a pace of 6.5 miles per hour. At this faster pace (higher intensity exercise), his energy is supplied only 25 percent from fat sources and 75 percent from carbohydrate sources. On the surface, this would seem to validate the theory of a lower intensity-training zone that preferentially uses fat calories.
However, you need to know the rest of the story-
At the 3.5 miles per hour pace, the subject burned a total of 240 calories during his 30-minute walk. He therefore burned 96 total fat calories (40 percent of 240 calories = 96 calories). At the 6.5 miles per hour pace, the same subject burned a total of 450 calories during his 30-minute run. He therefore burned 112 total fat calories (25 percent of 450 calories = 112 calories), which exceeds the number of fat calories burned during the lower intensity exercise session. So when you multiply the percentage of fat used by the total number of calories burned, you always utilize more fat calories when training at higher exercise intensities (higher heart rate zones) than when training at lower exercise intensities (lower heart rate zones).
The whole truth is that the amount of fat you lose from your body fat stores is not determined by the type of calories burned but by the total calories burned. Let’s say this another way. The only thing that matters in body fat reduction is the difference between the number of calories you eat (including carbohydrates, fats and proteins) and the number of calories you burn (including carbohydrates, fats and proteins). Essentially, when you burn 3500 more calories than you eat, you lose one pound of fat.
So the next time you are asked to train at a specific heart rate in regards to burning fat, please feel free to reference this article! Contact us with any questions!