Of all the different bodily tissue-types, muscle uses by far the most energy. It therefore makes good sense to increase Energy Expenditure by increasing muscle activity. This will not only ensure that you will use more energy whilst you exercise, but it also increases your energy consumption afterwards, during rest. This is achieved by increasing your basal metabolic rate. A bigger, healthier muscle obviously needs more energy to maintain its basic chemical functions, even whilst you laze on your bed. Another fact is that muscle uses fatty acids in preference to glucose during rest for energy purposes. A lot more energy, however, is obviously required during its working cycle, and glycogen, the store form of glucose, is mainly used. To replenish these glycogen stores, fatty acids are sacrificed during rest and converted into glycogen.

The facts of the matter are that exercise does not ‘burn’ all that many calories. The goal of regular exercise should also not be seen as an attempt to do so. This may sound odd, but if one looks at energy expenditure, it becomes rather obvious. Many people who quench their thirst by downing an energy-drink after an exercise session consume more energy than what they have just expended by exercising. Even worse, they raise their blood glucose levels almost immediately. Not only does this prevent the utilisation of fatty acids as an energy source, it also encourages the secretion of insulin. (Remember that insulin, discussed in more detail in the section on hormones, is the hormone that promotes fat production and deposition)

Completing a marathon requires only about 2000 calories, which is almost as much as most people store as glycogen (glucose molecules bonded together in long chains) in their livers. A marathon runner could therefore theoretically complete an entire marathon without consuming any additional energy other than the glycogen stored in his liver, and without burning a single molecule of fat in the process. One kilogram of fat contains approximately 1600 calories of energy. If a person wants to lose 10 kilograms of body weight through exercise, he / she will theoretically have to run 8 marathons without eating anything during the process. (We certainly do not suggest that you try this method!)

So what on earth is the purpose of regular exercise, you may ask?

The effect that regular exercise has on hormones is its major advantage. Insulin levels are decreased by exercise, and glucagon levels are increased. (Do not confuse glucagon, the hormone, with glycogen, the store form of glucose)

Exercise has an ideal ‘fat burning’ zone, where the maximum use of fat as an energy source is achieved. This level is reached if your heart rate is kept at 70% of your maximum. (Your maximum heart rate can be determined by subtracting your age from 220)

Although the exact mechanism of how a muscle develops in response to exercise is not entirely understood, there is a distinct difference in the structural changes the muscle undergoes, as determined by either the absence or presence of oxygen. Endurance or aerobic training leads to a better blood supply (capillary density) and increased oxygen supply to the muscle, leading to greater endurance. Strength or anaerobic training, on the other hand, leads to greater muscle strength and size, and a greater tolerance for the by-products produced by metabolism in the absence of oxygen.

Aerobic exercise at your ‘fat burning’ zone may be ideal when burning fat as an energy source, but higher levels of exercise intensity, decrease insulin levels and increase glucagon levels even more.

Anaerobic exercise is even more strenuous and stimulates the release of one of the most powerful fat-burning substances in the body, namely growth hormone.

Regular exercise also improves life expectancy. This is achieved by improving heart and lung-function, which leads to better blood circulation and ultimately increased tissue oxygenation. This is even applicable, and has been statistically proved to be so, with people who start exercising late in life.

The lesser-known advantages of regular exercise include its ability to regulate your normal sensation of hunger (satiety) and the prevention of bone-mineral loss (osteoporosis). It also reduces stress and depression, thereby improving general well-being, self-confidence and self-image. Emotional well-being, in turn, leads to better self-control in all aspects of your life, but especially when it comes to deciding on your food intake.

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