How much fat can I expect to burn?

The speed at which your body can produce energy from fats, and the amount it can produce, depends on a number of things.

1. How fast your body can break down fats in adipose tissue into their component fatty acids. This requires oxygen, so you must be exercising aerobically.

2. How fast your body can deliver these fatty acids into muscle cells elsewhere in your body.

3. How fast the fatty acids are transported from the main area of the muscle cell into the little 'power houses' within the muscle cells (the mitochondria).

4. How many mitochondria there are in the muscle cells.

5. The number of fat burning enzymes in your mitochondria.

6. The proportion of muscle fibre types in your body. Different types of fibre are better suited to producing A TP aerobically or anaerobically. This is largely genetic, although it can be partially influenced by training.

Each of these factors can be improved and made more efficient by regular aerobic training. Over a period of time, aerobic training will make it easier for the body to break down fat and use it as energy during aerobic exercise. In other words, regular aerobic training makes a person a more efficient 'fat burner'. The body can then break down fats into fatty acids more readily, deliver them to muscle cells faster (because the number of blood capillaries serving the muscle increases), and also transport the fatty acids faster into the mitochondria. The number of mitochondria and fat burning enzymes within them also increases. This helps to make the fat preferring muscle fibres work more efficiently.

So, at any given exercise intensity (even at rest), the fitter you are, the more fat and the less glycogen your body will use. This is important because glycogen is in much shorter supply than fat. By using fat you can make your body's valuable glycogen stores last longer and thereby delay fatigue.

Each of these factors can be improved and made more efficient by regular aerobic training. Over a period of time, aerobic training will make it easier for the body to break down fat and use it as energy during aerobic exercise. In other words, regular aerobic training makes a person a more efficient 'fat burner'. The body can then break down fats into fatty acids more readily, deliver them to muscle cells faster (because the number of blood capillaries serving the muscle increases), and also transport the fatty acids faster into the mitochondria. The number of mitochondria and fat burning enzymes within them also increases. This helps to make the fat preferring muscle fibres work more efficiently.

Regular aerobic exercise can therefore increase the body's efficiency in terms of energy production, and help to keep body fat levels within a healthy range. This is why fat endurance athletes are few and far between! In contrast, athletes involved in anaerobic sports, such as power lifting or shot putting, often have higher body fat levels due to a lack of aerobic training.

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