High Intensity Versus Low Intensity

For Fat Loss

High intensity versus low intensity is a debate that has been battled for many years in the fitness industry. There are benefits to doing both. This article is a short examination of both methodologies with a slight slant towards one side, as you will discover.

How They Both Work to Help You Burn Fat

First of all lets look at sustained, low intensity exercise as a method for fat loss. When you perform an aerobic activity such as running, cycling, rowing, swimming etc. at a continuous pace you burn calories at an increased rate from that of at rest. These calories come from two sources, the first being glucose or glycogen, the second is fat. This is what we want when trying to lose or maintain body weight, fat burning.

The greatest percentage of energy comes from fat when performing at this rate. This is why many people believe that low intensity cardiovascular training is the only real way to burn fat. This is not true, however it is one method that does indeed work.

As a further benefit, low intensity exercise at a continuous pace causes adaptations to the body’s systems. These adaptations include increased fat burning efficiency through the creation of extra mitochondria and an increase in size of the same. Mitochondria are like tiny fat burning factories within a muscle cell designed to metabolise fat for use as fuel, hence increasing capacity for greater endurance performance and decreasing body fat at the same time. There are other adaptations but this is a primary one.

High intensity exercise such as intervals, strength training, high intensity circuits, fartlek training etc. is a little different in its fat burning mechanism. When you perform this form of training you burn calories from both sources, however the number of calories it takes is much greater than for that of low intensity, continuous exercise. The greatest percentage of fuel for high intensity training is sourced from glucose or glycogen, which are essentially carbohydrates. This doesn’t sound good, however it is not the full story.

During a high intensity session the body will actually burn more overall calories. Although a higher percentage comes from carbohydrate, the body will still utilise more fat due to the large difference in caloric expenditure. So essentially it is more time efficient for short term fat loss.

As a further benefit there is what is referred to as EPOC. This stands for excess post-exercise oxygen consumption. This is when your body is burning extra energy for hours after the sessions has finished. This is what contributes to most results in a fat loss program. EPOC is greatly increased as intensity increases.

So What Should You Do? What are the Benefits of Each?

High intensity versus low intensity for fat loss is a hard one to come to a concrete distinction from. They both work, they just work in different ways. I always recommend to most people to do a mixture of both with a focus on leaning towards the high intensity side.

Take a look at low intensity exercise. This is slow, steady and continuous. An effective aerobic training session would generally be at least 30-40 minutes and needs to be done very frequently to have any real benefit. This form of training works and can create great adaptations such as increased number and size of mitochondria. This results in the efficient use of fat as a fuel source, giving you a body that literally burns up fat even while at rest. However the downside is that endurance training can cause a loss of muscle mass. This loss of muscle mass will generally lead to decreased strength, speed, power, balance etc. Essentially you are left with a skinny, wasted body that can run a long distance at a moderate pace.

Now lets look at high intensity. This sort of training can be kept to very brief sessions, 20 minutes or less. This form of training is practical for most people because training frequency is decreased and the large volume needed to create a noticeable increase in mitochondria density during aerobic work becomes void.

High intensity training promotes maintenance and often increases in lean muscle mass, even if what you’re doing is not strength training. High intensity exercise also allows a corresponding increase in both aerobic and anaerobic capacity. By increasing muscle mass and work output a person is able to burn more fat in a given time frame, including at rest.

Putting it Into Practice

So what do you do? You know the facts about high intensity versus low intensity for fat loss but have no clue what would work for you. So if you have loads of time and are not worried about getting thin and decreasing performance in various areas then by all means take up endurance exercise. By doing high volume you are teaching your body to burn fat as a fuel source.

For most people high intensity makes a lot more sense, at least a program that contains at least some of it. High intensity intervals will promote a laboured recovery, which costs calories. Further, high intensity training generally includes building a certain amount of lean muscle tissue. This helps with more immediate increases in metabolism and the capacity to fit more work into a shorter time period.

High intensity versus low intensity was simply to provide contrast between the two. Further programs, articles and workouts are posted to the workouts and programs section.

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