Atkins Diet and other Low-Carb based plans

by Panos Prokos, MS, CSCS

Note: I would like to make clear at this point that the following article does not entirely cover the subject of Low-Carb diets. It is in fact an excerpt from my substantially more detailed and technical article titled "Exercise and Metabolism" which you can obtain by emailing me directly. I have purposely trimmed down most of the technical aspects and jargon of the original article in order to make it easily understood for most people. At the same time I have trimmed out a big part of it in order to keep the article down to a size that will make it readable in a reasonable amount of time. That being said, below are the main points of the original article.

Before we start lets get a couple of important points out of the way: First, this article neither condemns nor recommends any Low-Carb diet. Instead it provides facts and questions about this type of diet, facts and questions which will hopefully make you derive your own conclusions. Secondly, during the course of this discussion it will be always assumed that the theories and principles of human metabolism are unquestionably valid and as such can not be dismissed or ignored.

The low carbohydrate diets have caught up quite rapidly within the American culture. During a period of less than 7 years, the grocery store shelves have been stocked with low carb alternatives ranging from low carb beverages to low carb candy bars. This is a direct result of the trend of Low-Carb diets which although have been in existence from the early seventies and have, in fact, been used throughout the European continent particularly during the eighties, have only recently begun flourishing in the United States. Pioneers of the trend were Dr. Michael Eades and Robert Atkins, two exceptional physicians who investigated the possibility of shifting the paradigm of carbohydrates being the primary source of energy for human kinetic function to using fat as the main source of energy.

We should point out a very important point here: We need to establish our audience. Who are we referring to when we are discussing this paradigm shift? Are we talking about the average sedentary individual, are we talking about the average fitness enthusiast who spends an average of 1 hour for 4 times a week in the gym, or are we talking about the competitive athlete for whom exercise may occupy 15-20 or more hours a week? It is a very important distinction as each one of these individuals has special caloric and nutritional needs that significantly different form each other. Given that, lets start by examining what is the main function of carbohydrates.

When simple carbohydrates such as sugars get consumed through a meal they undergo a digestive process (detailed in my complete original article) and eventually end up being stored as glycogen either in the liver or inside muscle cells. The amount of glycogen inside muscle cells during rest in a typical adult male is between 1.5 and 1.75 grams per 100 grams of muscle tissue. This glycogen stored in the muscle cells remains there until it is called upon to supply energy for muscle movement. When the call is made, the glycogen is converted into glucose and undergoes the process of glycolisis after which it produces Adenosine Triphosphate (ATP). Adenosine Triphosphate is the only source of energy in the body that can be used for muscular contraction. Our muscles contain stored amounts of ATP which are so small that they can be depleted during the first few seconds of intense exercise. A typical runner during a 200 meter dash will completely deplete his or her ATP muscle reserves. On the other hand, the average sedentary individual will probably never do so within the course of a whole day.

Once ATP in the muscles is depleted, something that happens within 15-20 seconds of continuous intense muscular contraction such as a dash race for a runner, a 50 meter sprint event for a swimmer or a brief flat or downhill race opening for a road cyclist, the body will initiate a second process of energy production called anaerobic energy metabolism. Again, I will not go into technical details in this article but if you want to learn the complete process of anaerobic metabolism get my original article and you will find the whole scoop with all the technical jargon. In any case, this second stage of energy production known as the anaerobic metabolism, utilizes the glycogen stored in the muscles in order to initiate ATP production since the original ATP has now been depleted. This process is the primary source of ATP creation between the next 20 seconds and up to 10 minutes assuming of course that the athlete continues the muscular work. It should be mentioned that although this anaerobic process does not cease after 10 minutes it is becoming less and less important in the production of ATP as after the 10 minutes a third process of ATP production kicks into play. This third process of ATP production is known as aerobic metabolism and calls into play the fat and some more glucose which enter into a reaction in the presence of oxygen (hence the word aerobic) out of which we get more ATP. Remember that all this is taking place after the 10 minutes of intense and continuous exercise. In other words, this is something that will happen in a long distance runner or swimmer or within a cycling race, but it is quite unusual that the average individual will enter into this stage within the course of a day.

Do you begin to see the importance of establishing our audience? Now, if we assume that our above mentioned athlete has been on a carbohydrate restricted diet and therefore does not have an adequate supply of glycogen in his or her body he or she is going to be in a energy debt as the body will not be able to produce ATP from the fat resources alone (that is because the process of creating ATP through fat reserves is very slow but again, this is discussed in detail in my original article) and our athlete will run out of energy and he or she will experience what is most commonly known within the athletic community as "bonking".

The average sedentary individual and probably the fitness enthusiast who limits his or her aerobic training to less that 15 minutes and trains primarily with weights will probably never have to be concerned about this.

Point in case: If you are a sedentary individual or a fitness enthusiast who is involved in medium intensity aerobic training with a duration of 10 minutes (for the aerobic training part only), you may be fine on the Atkins diet or any other Low-Carb diet. If on the other hand you are involved in intense resistance exercise followed by 10 minutes or more of intense aerobic activity such as a typical spinning class, you will not be able to perform adequately by being on a Low-Carb diet.

Now lets see what will happen when our athlete gets in the aerobic metabolism stage and his or her body enters Krebs cycle and starts metabolizing fat tissue to create ATP. Since the majority of glycogen has been depleted, the body is looking into alternative sources of constructing ATP. Fat being the first one, and remaining blood circulating glucose being the second, but there is also a third one: The precious muscle tissue. The muscle tissue can be "torn apart" for energy production under certain circumstances. When the glycogen storage has been depleted, and the amount of glucose in the blood has consequently been decreased below a certain limit, the cortex of the adrenal gland secrets the hormone cortisol whose main function is to aid in the maintenance of blood glucose. However, cortisol signals the breaking down of muscle tissue back into its building blocks the well known amino acids. During this process, certain amino acids, principally alanine, are released from working muscles and transported by the blood to the liver, where they are converted to glucose. This glucose can now enter the Krebs cycle and aid in the production of ATP.

Do you start seeing the extend of the problem? Now, not only has the athlete run out of his or her primary energy sources and is low on ATP as explained above, but has also started breaking apart his or her precious muscle tissue in order to keep his or her energy levels high enough to sustain further training. In other words we have the initiation of a bootstrapping effect that results in the athlete entering a catabolic state and instead of making muscle gains is working hard towards his or her muscle loss!!

As I explained in the beginning, the above is a simplified description of the metabolic process for the creation of the energy unit ATP, but if you want to learn the whole technical science behind it, you can read my original detailed article..

To summarize, if you are a sedentary individual who is looking to lower his or her weight and is not concerned about muscle loss or water weight reduction, and does not want to experience the numerous positive effects of exercising, then a Low-Carb diet such as the Atkins may serve you fine. If on the other hand you are an active individual who is following the correct way to weight loss, in other words the combination of aerobic exercise and correct resistance training, you will not be able to perform to adequate levels while being on a Low-Carb diet. As a matter of fact, your exercise may prove to be counterproductive as it will lead to an inevitable loss of muscle, in other words you will be working out to decrease your own muscle tissue.

In order to succeed, you will need to assume a correct nutritional regime consisting of the right kind of carbohydrates and that means minimizing sugars and starches and increasing fibrous carbohydrates such as vegetables (not fruits), while at the same time ensuring that you are taking your fats from sources that do not provide you with saturated fats and/or hydrogenated oils, and at the same time consuming enough good quality (with a correct amino acid profile) protein. Sounds complicated, and that is why your best bet would be to consult a Nutritionist or Dietitian familiar with the nutritional requirements for athletes.