While it is well-known that exercise is a necessity for effective weight loss, there is quite a bit of conflicting information as to what kind of exercise and how much of it will produce optimal fat burning. Experts often disagree as to what the “correct” exercise is for maximum weight loss. This disagreement is often due to a misinterpretation of research that only gives a part of the whole story. In addition, different individuals will actually benefit from different exercise programs, so universal exercise recommendations really cannot be made.

Let’s begin with what the current research on exercise physiology tells us. It is well-established that it takes approximately 30 minutes of any kind of exercise for the body to burn off its glycogen (stored sugar) reserves and begin burning fat. So, most experts recommend at least 30 minutes of exercise, and generally 60 minutes or more may be recommended to get a good amount of fat burning. Now, if you are going to be exercising for 30 to 60 minutes, or maybe more, what type of exercise would you be able to do for that length of time? It probably would have to be low to medium intensity. In other words, you’re probably not going to be able to run full speed or do any other type of high-intensity exercise for 30 to 60 minutes without a rest, unless you happen to be an elite athlete, and even then you’d be struggling. So, by default, the common recommendation for exercise to lose weight has been 30 to 60 minutes of low to medium intensity aerobic exercise. Aerobic translates to “in the presence of oxygen”, which in common language means that aerobic exercise is any type of activity that you can do without gasping for breath.

In recent years, some experts have changed their recommendations to using a more intense anaerobic (“without oxygen”) exercise program for weight loss. This would include things like intense weight lifting, and something called “interval training”. Interval training involves brief bursts of high intensity activity with periods of rest or low intensity activity in between. For instance, your could sprint at full speed for 30 to 60 seconds and once you were winded, you could walk at an easy pace for a couple of minutes until you could catch your breath, then repeat the cycle several more times.. Since this type of exercise is much more physically demanding, it is done over a much shorter overall workout period – perhaps 20 to 40 minutes (with half or more of that time being rest or low intensity activity), as compared to the 30 to 60 minutes of continuous activity as recommended for aerobic exercise. The question is, how do the two types of exercise compare in terms of their ability to promote fat burning?

The aerobic exercise promoters point to the research that was mentioned earlier that has shown that any exercise, no matter how intense requires at least 30 minutes to use up the body’s stored glycogen (the body will normally burn glycogen before it will burn fat) before fat burning can begin. So, they say, short periods of even highly intense exercise won’t burn much fat and is therefore not a good choice for promoting weight loss. But they are only seeing part of the story.

It is true that you must exercise for at least 30 minutes to begin to achieve fat burning – but that’s at the time you are exercising. Brief bursts of intense anaerobic exercise does something that even quite a lot of low to medium intensity aerobic exercise does not. Intense anaerobic exercise stimulates the production of growth hormone, which is a strong stimulator of fat burning. The thing is, the release of growth hormone triggered by intense anaerobic exercise comes 24 to 48 hours AFTER the exercise, and then it produces considerably more fat burning than is possible with all but extremely long periods of low to medium intensity aerobic exercise.

Because of this effect, most people will lose weight much more easily by doing shorter periods of more intense exercise. 20 to 40 minutes of heavy weightlifting, interval training (which could be done on foot, on a bicycle, swimming, kickboxing, etc. Any kind of activity in which there are periodic bursts of intense exertion interspersed with rest periods, or periods of low intensity activity is typically preferable in the long run for weight control than even long hours of lower intensity aerobic exercise.