How Hard Should You Work?

One of the biggest areas of controversy concerns how hard you should work in order to maximize the amount of fat you burn while you are working out. The truth is that whatever form of exercise you do, you will be helping your body to burn fat, not only while you are exercising but all the time. One school of thought is that if you work too hard, you won’t burn fat. This is based on the principle that because it takes a long time for the fat to be taken out of the fat cells, into the bloodstream, into the muscle and then finally broken down, you need to exercise for quite a long time in order to stimulate this process. In other words, by the time the fat has been taken to the muscle, you will have already finished exercising. There is a lot of scientific evidence to support this, and in principle it is true.

To maximize the amount of fat you burn while you are working out, you should aim to keep going for longer to give your fat cells more time to release their fat. You should also remember that if you do this regularly, you will be training your fat cells to release fat into the bloodstream to be used as fuel. In order to do this, you will need to keep the level of exercise fairly low to moderate—after all, Olympic gold medalist Carl Lewis could not run as fast over 1,500 meters as he does over 100 meters. In general terms, you should feel breathless but not exhausted.

There are several ways in which you can estimate how hard you are working in order to see whether or not you are burning fat. The first is to take your pulse rate while you are at the hardest point of the exercise. The problem with this, however, is that if you are moving around (jogging or swimming, for example), it is almost impossible to take your pulse accurately. You will also need to calculate in advance what your maximum pulse rate should be.

Obviously you don’t want to work at 100 percent. Research has shown that when we work at approximately 65 percent we burn the most fat. Sixty-five percent of 190 is 123. Therefore, if a 30-year-old reaches a level where the heart is beating 123 times per minute, he or she is likely to be in the “fat-burning zone”: what you need to do is to pedal away at a level that is comfortable and sustainable. Remember: It takes longer to start burning fat than just glycogen alone, so start gently and gradually increase the time you spend on the activity, until you can work at a comfortable level for 20 or 30 minutes. Rest assured, you will be burning fat. You will also be improving your cardiovascular system and reducing your risk of heart disease.

The second school of thought is completely different, but also correct. It is based on the total amount of calories burned during exercise. Having established that you burn a higher percentage of calories from fat if the level is low to moderate, we now need to look at the total number of calories burned overall during low- versus high-intensity exercise.

For every individual, there is a particular point at which we can no longer continue to work aerobically—that is, supply oxygen at the rate it is required. At this point, we then start to use the anaerobic energy system, which does not burn fat and in turn produces lactic acid in the muscle. This causes muscle soreness, which eventually stops the muscles from contracting. Whether or not you should walk or run to burn more fat, therefore, depends largely on your fitness level and on how long you are able to exercise.

In addition to this, you should remember that the total amount of calories burned will vary from one individual to another, according to the total body weight and the amount of lean body mass. One pound of muscle will require approximately 40 calories per day in order to function—excluding exercise. The more you exercise, the more calories the muscle will require—not just when you are exercising but throughout the day and night, as it repairs itself and starts to grow stronger. The result is a higher percentage of muscle on our bodies, so we burn more calories when we work out. This in turn means we burn more calories throughout the day and night, and so the cycle goes on. All these extra calories have to come from somewhere, and provided you are not eating more than you need, they will come from the body’s fat stores—the perfect way to lose weight.