Is your workout putting you in the fat burning zone or is taking you out of the zone? You might be surprised.
You body has two basic energy systems: The Aerobic and The Anaerobic.
The anaerobic system is used for short high intensity bursts, (e.g. sprinting, lifting weights, running up the stairs) while the aerobic system is used for long sustained activity (e.g. walking, jogging, sleeping).
It has long been thought that in order to burn fat you had to get into your "fat burning zone", typically after 20 minutes of continuous activity. However, this fat burning zone doesn't actually exist. You see when this whole idea came about researchers only looked at where the calories being burned came from, not what the total caloric expenditure was or how high of an "afterburn effect" (the total number of calories burn in the period of time following a workout that your body stays in a metabolically elivated state) was created.
Keeping the with the "fat burning zone" theory would mean that the best activity to burn the most calories from fat would be to sit completely still. Because at rest your body uses fat as the primary fuel source. If this worked we would all be thin, as the average American moves less and less each year. The problem here is that while fat may be the primary fuel source the caloric expenditure is very low and there is no elevated metabolic state.
On the flip side anaerobic activity, like weight lifting, will use more carbohydrate (muscle gylcogen) as the primary fuel source, but will burn a tremendous amount of calories and create an "afterburn effect" for up to 72 hours after completing your workout. In fact, the more intense the exercise the more calories burned and the greater the afterburn effect. This is why jogging, walking, and aerobics in general don't produce as good of results. While aerobic exercise burns calories it's not very intense. Nothing that can be done for longer than 30-60 second bursts falls into the anaerobic category, because if you could sustain doing it for longer than that you aren't working hard enough.
On a side note, all most all of the studies done on the caloric cost of exercise (amount of calories burned) have only looked at it from an aerobic perspective. When looked at from an anaerobic perspective it's has been found that the anaerobic caloric cost is much greater than the aerobic cost when looking at the same exercise.
Example: 150 pound female would burn the following calories per minute of each type of exercise:
1. Sitting still = 1.35 calories
2.Walking = 5.46 calories
3. Aerobics Class = 9.30 calories
4. Jogging = 13.05 calories
5. Jumping Rope = 13.35 calories
6. KB Snatch Intervals = 26.2 calories
What this tells us is that the more intense the exercise the more calories per minute burned, and this isn't even taking into account the afterburn effect, which will increase as the intensity increases.
So let's take this on step further. Our 150 pound female has the choice between a twenty minute KB Snatch Interval done at a 30 seconds on, 30 seconds off, repeated for 20 minutes. Or she can take a jog. If she chooses the KB Snatch Interval she will burn 524 calories in twenty minutes and create an afterburn effect that will stay in place for the next 72 hours. Or she can take a 40-minute jog and burn the same amount of calories, but not create as high of an afterburn effect and her elevated calorie burning will stop shortly after she stops running, unlike with the KB Interval.
Now does this mean that everybody needs to start doing KB Snatch intervals. No, the same results can be achieved through a metabolic circuits or strength training using non-competing supersets.
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