Exercise for fat loss

March 7, 2011

Please not that this article is targeted to the general population about “exercise and fat lost” only… Many other factors such as muscle mass, fat mass, nutrition and possible diseases also come into consideration when losing fat. Please do not hesitate to comment or email me if you have any questions on this topic or if you find any information that you might disagree with.

The most common question I get asked as a trainer is “what exercise must I do in order to lose fat?”

Well… there are a thousand ways to train and/ or exercise and therefore there is no recipe I or any trainer can put out there that will work for everyone. Each person needs to have a unique program designed for them alone mainly due to personal likes and/ or dislikes. However, to put it simply, there are two types of exercise…
1) Low Intensity
2) High Intensity
Most people who want to lose fat will perform low intensity exercise because they are told that low intensity exercise burns fat. While this is true, I can confidently say that it is not the most effective way of losing fat. Lets go to science…

FAT vs CHO / low vs high intensity

So by looking at the graph above, we see that a high percentage of fat and a low percentage of CHO is being used at low intensity exercise and a low percentage of fat and a high percentage of CHO is being used at high intensity exercise. Then we see the crossover concept at roughly 50-65% of the VO2max where both fuel sources are being used evenly… So at first glace your probably saying, well if fat is the main fuel source at low intensity exercise, then this is what I should be doing to burn fat. However the truth is that you will actually burn fat more effectively by performing high intensity exercise.

“How?” you ask…

Well, its not what happens during exercise that counts, but rather what happens after exercise that counts and so it’s after exercise where fat burning is most effective. Hence, you could say that exercise is something that “sets up” the chemical reactions that occur within the body for many hours after training. Again, lets go to science…

What you are looking at in the graph above is the EPOC (highlighted in purple or after the vertical red line) which occurs after cessation of exercise. The EPOC is basically the oxygen recovery period or the period of time it takes for the oxygen to be recovered to “resting state” after exercise. As you can see in the top graph, light to moderate intensity exercise will result in a fast recovery period (roughly 1 hour) basically because you have not trained at a high percentage of your VO2max (in other words, you have not consumed a high percentage of oxygen during training). Whereas in the bottom graph we see that high intensity exercise will result in a much longer recovery period (can be from 7hours plus) because you have trained at a really high percentage of your VO2max (in other words you have been consuming a lot of oxygen during your training). You could say that while the EPOC is raised the metabolic rate is raised, and while the metabolic rate is raised fat is being burned because fat is burned when the metabolic rate is up. Having said all this, the best way to keep your metabolic rate raised for a longer period of time is by performing high intensity exercise. Therefore the most effective way to burn fat (in relation to exercise) is by performing high intensity exercise.

Many biological terms are used and may be difficult to understand. I have written this article in the best way possible for all to understand. Please leave me a comment if you have any questions regarding this article and I’d be more than happy to assist you with answers.

The purpose of this article is to:
1. Explain why the recommended daily intake of carbohydrates (CHO) is important for low intensity (long duration) exercise.
2. Explain why the recommended daily intake of carbohydrates (CHO) is important in regards to fat loss.

Below is the biological process of what happens within the human cells when the recommended daily intake of carbohydrates is not met.

Carbohydrates is known as a sugar and is absorbed from food when it reaches the intestines. This sugar travels in the blood as glucose, however can also be stored in the human muscles and liver as glycogen. If you do not eat carbohydrates then you will have decreased carbohydrate/ glycogen stores which will decrease the rate of glycolysis. Glycolysis is the breakdown of glucose to pyruvic acid which is then converted to Acetyl-CoA and occurs in the cytoplasm of the cell. Hence, by decreasing the rate of glycolysis you will decrease the quantity of pyruvic molecules being made. So by decreasing the quantity of pyruvic molecules being made, we are now decreasing the quantity of “material” to make the intermediate substrates of the “krebs cycle”. The krebs cycle occurs in the mitochondrial matrix of the cell and is where energy is made from both carbohydrates and fats. Both carbohydrates and fats are converted to a substance known as Acetyl-CoA which goes through the krebs cycle to make energy. If there is a decreased quantity of “material” to make the intermediate substrates of krebs then the functional rate of krebs is inhibited. Now we mentioned before that krebs is where energy is made, so if the krebs cycle is inhibited then we can’t make energy.

So now your asking… “well how is this related to fat?”

A process known as lipolysis is the breakdown of fatty free acids into acetic acids. Acetic acid is converted to Acetyl-CoA which then needs to go through the krebs cycle so it can be converted to energy as i mentioned before. However since the krebs cycle is inhibited due to not eating enough carbohydrates, the Acetyl-CoA from fats has nowhere to go and therefore fat is not being burned and energy is not being made.

Having said all this, the quantity of energy being made from fat is dependent upon the rate of carbohydrate metabolism.

To explain the purposes again…
1. The main fuel used in low intensity (long duration) exercise is fats, and therefore carbohydrates is required in order to keep the krebs cycle active so fats can be processed into energy for this type of exercise.
2. In order to burn fat for fat loss, the fats need to go through the krebs cycle. So once again carbohydrates is needed to keep the krebs cycle active so fats can be burned for fat loss.