ARTICLE - THE TRUTH ABOUT THE FAT BURNING ZONE

SUMMARY

THE ARTICLE

Many of us have heard about the “fat burning zone.” We are often told that there is a level of exercise that will burn more of our fat than carbohydrates, and that we will lose weight if we strictly adhere to that zone when working out. We see claims about the fat burning zone everywhere, including on the equipment in our gym, and we read about it in fitness articles all over the Internet. The fat burning zone is supposedly achieved by working out at between 55-65% of your maximum heart rate, a rather low intensity level of exercise.

The basis of the “fat burning” name is that at this low exercise intensity, your body uses a greater proportion of fat than carbohydrates for energy. Then, as your exercise intensity increases, your body shifts to using more carbohydrates for energy. This is in fact true, and it has led many people to believe that they should exercise only in the fat burning zone in order to lose body fat and therefore lose weight. This belief has even spread to fitness instructors and equipment manufacturers, which is why we see a “fat burning” program on our exercise bikes, stair machines and treadmills, and “fat burning” classes in our gyms. However, the fat burning concept is misunderstood.

While it is true that more fat than carbohydrates is used for energy while exercising in the fat burning zone, very little of both are used at this intensity. At a higher intensity, you burn many more overall kilojoules, including fat kilojoules, than you do in the fat burning zone.

For example, in the fat burning zone of 55-65% of your maximum heart rate, your body may burn 50% of the kilojoules from fat, and 50% from carbohydrates. At a higher intensity, your body may burn only 35% of kilojoules from fat. So let’s say you burn 1000 kilojoules by exercising at the lower intensity for 30 minutes, meaning you burn 500 fat kilojoules and 500 carbohydrate kilojoules.

However, if you burn 2000 kilojoules at the higher exercise intensity level in 30 minutes, you are burning 700 kilojoules from fat and 1300 from carbohydrates. So you actually burn more fat kilojoules at the higher intensity than in the supposed “fat burning” zone.

There is also the question of time spent exercising. A study published in the Journal of the American Dietetic Association by Ballard et al in 1995 compared two groups of exercisers. One group exercised at 40-50% of their maximum capacity (low to moderate intensity) and another group that exercised at 80-90% of their maximum capacity (high intensity). Both groups exercised until they had burned the same number of kilojoules. The high intensity group exercised for 25 minutes and the low intensity group for 50 minutes, and both groups lost the exact same amount of fat. So the high intensity group only had to exercise for half the time to get the same result in terms of fat loss!

But that’s not the only benefit of high intensity exercise. By exercising at a higher intensity level, you actually turn your body into a fat burning machine during the hours you are not exercising. This does not happen when you exercise at a lower intensity. Working out at a higher intensity raises your metabolism all day and night long, which of course means even more fat is burned. Studies such as those by Tremblay et al (1995) have shown that up to nine times more fat is burned with high intensity exercise, due to the effect of exercise on your metabolism after you work out. These researchers also noted that high intensity exercise may suppress your appetite, which can also assist in fat loss.

If all that weren’t enough, depending on your current fitness level, exercising at a higher intensity will significantly improve your cardiovascular system and overall fitness level while lower intensities may not.

If you are new to exercise, or if you have special medical considerations, exercising at a higher intensity may not be appropriate for you. Novice exercisers can gain fitness benefits from exercising at moderate intensities, but as your fitness level increases you will need to increase your intensity level, frequency, and duration. This will both burn more fat and continue to improve your cardiovascular system and overall fitness level.

If you are over age 50 or have special medical considerations such as obesity, chronic illness or injury, check with your doctor before beginning any exercise program. He or she will be able to advise you on the best exercise intensity levels for your specific needs and weight loss goals.

So now you know: don’t believe everything you read about the fat burning zone. If you are healthy and reasonably fit, you will burn more fat at a higher exercise intensity level, and you will gain the additional benefits of round-the-clock fat burning and a significantly improved fitness level.

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