Copyright (c) 2006 Ainsley Laing
Over the weekend, a really good friend was discussing how
he "just can't seem to lose 2 kilos". He feels that it is
fat weight and we discussed ways in which he can change his
workout to optimize fat loss. This got me started thinking
about how many different methods of fat loss and fads have
come and gone over the many years that I have been a
fitness instructor.
If there is one thing I have learned exercising
regularly over time will work to burn fat. The methods that
work for each individual vary depending on the individual's
weight, cardiovascular fitness level, activity level,
metabolism, muscle development, size and even gender!
For all of us, though, if we eat more than our body
requires we either store it as fat or have to "burn it
off".
The body at rest uses energy (calories) to power the
organs, brain, cardiovascular system, immune system and
skeletal muscle. In other words, all of the cells of the
body require energy. The rate in which the body uses energy
to function is known as the basal metabolic rate. There
are two other areas of calorie requirements, one known as
the thermic effect of eating (energy required to digest
food) and the thermic effect of exercise.
So how does the body convert energy for use during
exercise? There are 3 principle metabolic pathways, which
are the ways in which the body produces Adenosine
Triphosphate (ATP). I promise not to go too technical here
and risk boring you…
1. The ATP-PCr System
This is used during the first few seconds of exercise.
Creatine phosphate (PCr) in the blood is used to produce
ATP which powers the cells.
2. The Glycolytic System
Glycolysis means the breakdown of glucose. The body uses
this system for the first few minutes of exercise. If the
exercise is very intense (say sprinting), glucose in the
blood is used without oxygen and the by product of this
will be lactic acid. After a while, the lactic acid
accumulates (the burning sensation in the muscle) and leads
to muscle failure. This is known as anaerobic or fast
glycolysis. If the exercise is less intense (jogging),
glucose in the blood is used with oxygen to produce ATP and
the by product will be pyruvate which then is used by the
oxidative system below. This is known as aerobic or slow
glycolysis.
3. The Oxidative System
This system is has 4 parts which I definitely won't go into
except to give you the names: slow glycolysis (discussed
above), the Krebs Cycle, Electron Transport Chain and Beta
Oxidation It is in this system, fats more than
carbohydrates (glucose) are used to generate ATP. This
process is called lipolysis. The fat produces more
"energy" (ATP molecules), but also requires more oxygen.
What Does It All Mean?
In order to burn more fat, the intensity level must be
kept at a level that is sustainable for long enough to move
into the "fat burning zone" or Oxidative System.
Most people have about 2 hours of stored glycogen (glucose)
in the muscle when exercising at moderate intensity. So
it's safe to assume that unless you are running a marathon,
you are using both stored glucose and fat when doing your
aerobic training. This applies to whatever type of aerobic
training you choose.Weight training, on the other hand,
relies on stored available carbohydrate (glucose) because
the short duration/high intensity of each lift doesn't call
for the body to burn fat for fuel.
The argument that low intensity long duration exercise
burns a greater percentage of calories from fat still
stands. Example: a comparison of the calories expended by
the same person walking for 1 hour and jogging for 1 hour
reveals that the walking burns a much greater percentage of
calories from fat although the overall calorie expenditure
is lower.
In terms of just pure calorie consumption during exercise
the more oxygen you use the greater your calorie use. If
we look at the Oxidative System which uses fat, but
requires more oxygen to do, we can infer that working out
at medium intensity for longer durations will burn more
calories AND a higher percentage of fat.
The current thinking is that the more muscle groups engaged
during the activity (example: aerobic dance with arms and
legs), the harder the body works requiring more oxygen and
more calories. Do it long enough, the body will burn a
higher percentage of fat.
There's a lot of discussion about the "afterburn" or the
thermic effect of exercise recovery. Yes, the body does
burn energy to recover. A more intense workout requires
more energy to recover hence more calories burned after
the workout.
There are many fitness programs that advocate interval
aerobics for fat burning. There are just as many that
advocate long duration aerobics for fat burning. I
advocate a combination of the 2. Both will burn fat. Each
has benefits beyond fat burning.
Interval training increases your cardiovascular strength,
output, heart rate recovery and produces a stronger
"afterburn".
Long duration trains the cardiovascular system to sustain
an increased load for a longer period of time and teaches
the body to convert fat to energy more efficiently for use
during exercise (endurance).
Whatever aerobic activity a person does, the key is to keep
doing it. Why? The more a person exercises, the more
efficient the body becomes at converting and using
available carbohydrate and fat. So… regular aerobic
exercise over a long period of time is more important for
fat and calorie burning than which method used.
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About the Author:
Ainsley Laing, MSc. has been a Fitness Trainer for 25 years
and writes exclusively Body for Mind eZine. She holds
certifications in Group Exercise, Sports Nutrition and
Personal Fitness Training. To see more articles by Ainsley
visit http://www.bodyformind.com
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