LESS EXERTION + MORE PLANNING = LESS FAT

If you think putting on runners and taking a high-intensity jog around the block is a good way to lose weight, you’re wrong. It will increase your fitness and tone muscle, but it is not the most effective way of liquidating unwanted fat.

The old theory that the harder you exercise the more fat you burn has been replaced by a newer theory that requires less exertion but more planning. The new theory turns the old truth on its head. Basically, you don’t have to huff and puff to use up fat. The key is to change the intensity halfway through the exercise.

It’s all about burn rate. After 40 minutes of intense exercise you will be sweating, exhausted and congratulating yourself on a good workout, but you will have burnt very little fat. Had you spent that time differently you could have burnt much more.

In simple terms, it would have been more efficient to do 20 minutes of fairly intense exercise followed by 20 or even as much as 30 minutes of moderate exercise. In that moderate phase, fat would have begun to burn.

During exercise the body draws energy primarily from two sources: glucose and fat. The two are different fuels and the way the body burns them is analogous to the way a fire burns paper and wood.

Glucose is like paper. In a fire paper is quick to ignite, burns at high intensity and is used up rapidly. Fat is like wood, slow to get going but more effective as fuel over a long period. In the initial stages of an exercise session the body uses both glucose and fat.

As the duration of the exercise increases, a greater proportion of fat is used. During a sprint, for example, the body uses 80 per cent glucose and 20 per cent fat. During a 2-hour walk, the proportions are reversed and 80 per cent fat is burnt.

Glucose, which is stored in the liver and muscles as glycogen, is essential for the brain and the nervous system. For this reason it is always readily available and, to some degree, protected. Rather than allowing glucose stores to diminish, the body switches to using fat.

It is best to exercise first thing in the morning, before glycogen stores have been replenished by breakfast. Exercise then will result in a greater proportion of fat being used as fuel. While the amount of intense exercise necessary to burn fat varies depending on a person’s fitness, exercise history and metabolic rate, it is generally true that fat burns best during long periods of moderate exercise.

An easy way to plan exercise is to use the ‘perceived exertion scale’. This is a subjective measure of effort from one to 20, with 20 being the equivalent of running uphill at full speed with the wind against you. The glycogen depletion method suggests that the first 20 minutes of exercise be done at a personal 14 or 15 on the perceived exertion scale. For many people this would be a light jog or a power walk.

For the next 20 or 30 minutes, the method suggests a drop to an 11 or 12. This might be a walk that is determined enough to qualify as exercise but relaxed enough for you to be able to talk at the same time.

The program also focuses on raising metabolic rate. Metabolism is the ‘engine room’ of the body, and at rest, the average person has a metabolic rate that burns about a calorie a minute. The beauty of exercise is that it not only stokes up the metabolic rate, but it also keeps it partially raised for the next 14 hours.

Some take a slightly different view and suggest that the entire exercise session should be at a moderate intensity, which would be a 12 or 14 on the exertion scale. Long periods of slow movement, whether continuous or accumulated, are likely to be most effective in burning fat.

Overall, the message to those who want to burn fat is ‘keep moving’.

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