Diet and Nutrition

The Carbohydrate Conundrum

There are only a handful of things in life that I can say with 100% confidence are true:

1. Jessica Alba is smoking hot.

2. Her boyfriend is a lucky son-of-a-bitch.

3. The majority of people are completely confused when it comes to the topic of carbohydrates.

On one end of the spectrum, we have those people since the 1980’s who have advocated diets high(er) in carbohydrates, claiming that as long as you don’t eat a lot of dietary fat, you won’t get fat. People took the whole concept out of context and ended up overindulging on fat-free cookies, thinking they were a guilt-free pleasure. End result? An epidemic of obesity and type II diabetes that is costing the Healthcare industry billions each year. On the flip side, we now have the majority of “experts” who advocate fad diets (that focus on short-term fixes rather than long-term results) that are almost deficient in carbohydrates (Atkin’s, Southbeach Diet, etc) to the point where people curl up into a ball and cry for mommy at the mere sight of the word.

Who is right? Personally, I believe that people all too often tend to swing the pendulum too far to either side and need to bring focus back to the middle in some way. Both high carbohydrate and low carbohydrate diets have their place and it really comes down to the individual. However, the purpose of this article isn’t to take part in this ongoing debate, but rather to give you a solid reference point about what role carbohydrates play in your diet. What are they? What are the different types? Are carbohydrates “needed” in the diet? How are they metabolized? And most importantly, how can they be optimized to enhance performance and promote lean muscle gain?

The Exciting and Thrilling World of Carbohydrates (a hint of sarcasm)

Certainly it would be absurd to write an article on carbohydrates (CHO) and not first briefly discuss what they are and the different categories of each. To put it simply, carbohydrates are a superb source of energy for the body.

However, at the lowest level of cellular function, the only form of energy that the cells of your body can use directly is a big “sciency” word called adenosine triphosphate (ATP). The body has three (well, technically four) distinct pathways to produce ATP. The creatine phosphate system (CP) is the easiest way, providing fuel for quick and powerful bursts of energy up to twenty seconds. Glycolysis (breakdown of glucose) is the next one in line and can be divided into anaerobic glycolysis (without oxygen) and aerobic glycolysis (with oxygen). Anaerobic glycolysis is the primary energy source in activities lasting between 20 seconds and two minutes, and continues to “aid” in supplying energy lasting up to ten minutes. Aerobic glycolysis starts to kick in after about five minutes and is the predominant energy system utilized during this time.

Lastly, there is the oxidative system (fat), which is the most efficient fuel source for the body, providing fuel for long duration endurance events. However, because this article deals with carbohydrates (glucose) and how they can be used to enhance performance, I am going to be discussing them solely.

Upon consumption, carbohydrates have one of three fates:

  1. Broken down immediately upon ingestion and converted to energy to fuel activity.
  2. Stored in the liver or muscles cells and converted to glycogen to be used later.
  3. Under extreme (read: chronic overeating) conditions the remainder are converted into triglycerides and transported to adipose tissue and stored as fat . (1)

As such, carbohydrates themselves can be divided into a two main “categories”….simple and complex. They can also be further divided into “sub-categories,” based upon their chemical make-up or structure.

Simple Carbohydrates

Simple Carbohydrates include naturally occurring sugars in fresh fruits and some vegetables and in milk and/or milk products (as well as sugars in concentrated form such as honey, corn syrup, or table sugar). Simple carbohydrates can be divided into two sub-categories: monosaccharides and disaccharides.

Monosaccharides are known as simple sugars. These include: (2)

Glucose: is a natural sugar found in food and also goes by the name of dextrose of blood sugar. It’s also the main carbohydrate used in the body for energy and the production of ATP.

Fructose: also known as fruit sugar, is the sweetest naturally occurring sugar, estimated to be twice as sweet as sucrose (see below). Fructose is absorbed slower than glucose because of its lengthy metabolic pathway in the liver. As such it has often been recommended to not use fructose as a main source of CHO post-training to replenish glycogen stores.

Galactose: unlike glucose and fructose, galactose is not found in plants, but rather only in dairy products.

Disaccharides are formed from two monosaccharide molecules. These include: (2)

Sucrose: also known as table sugar, sucrose is the most commonly found sweetener in the industrialized world. And it’s also the one of the main causes of obesity because it’s found in all the foods that most people tend to OVEReat (candy bars, pastries, cakes, etc).

Lactose: found in milk and other dairy products. Unfortunately, as many of us grow up, production of lactase gradually ceases. And we are then unable to metabolize lactose and as a result, gastrointestinal discomfort ensues in the form of embarrassing first date stories.

Maltose: also known as malt sugar and found in various cereals, beers, and germinating grains. And I am sure the only word many of you saw in that last sentence was beers.

Complex Carbohydrates

Complex Carbohydrates basically entail your starches, as well as fiber. Complex carbohydrates (particularly starches) tend to be a bit of a misnomer in that many people are under the impression that complex=good, and simple=bad. While this assumption does hold SOME merit, it’s not inherently correct. Complex basically refers to a plethora of glucose molecules crammed together (rather than just ONE or TWO as with simple carbs).

Take white bread for example (which is a starch and hence considered “complex”). White bread is nothing more than HIGHLY processed flour, which the body can easily break down into glucose molecules due to the fact that the bonds are broken down so easily (simple carbs). In essence, eating white bread is kind of like eating simple carbs. Starting to see the paradox?

But I digress. Complex carbohydrates can also be divided into a few sub-categories:

Polysaccharides
- formed from multiple chains of monosaccharides. These include: (2)

Dietary fiber can also be classified into two separate categories: soluble and insoluble.

Soluble Fiber - mixes well with water and helps to prolong stomach emptying and enhances feelings of “fullness” (satiety). Soluble fiber also lowers total cholesterol (specifically LDL’s, or “bad” cholesterol). Examples would include: rolled oats, oat bran, dried beans, nuts, psyllium husk, various fruits and vegetables.

Insoluble Fiber - does not mix well with water and helps with moving bulk through the intestines and keeps you “regular.” Examples would include: fruit skin, green beans, flax seeds, and whole wheat products.

What’s interesting about fiber is that unlike “regular” carbohydrates which yield roughly 4 calories per gram, many people have heard or are under the assumption that the body can’t derive any calories from it. On the contrary, it has been shown that various bacteria found in your gut breaks down fiber and it has been given a rough approximate caloric value of 1.5-2 calories/gram (3). However, unless you’re consuming a TON of it per day, you can generally ignore the caloric value of fiber.

Carbohydrates: “Can’t Live With Them, Can’t Live Without Them.”

Now that we know what carbohydrates are and the different types, we can now delve into the more “exciting” stuff and see how they can be utilized to enhance performance and aid in lean muscle gains.

Carbohydrates serve many integral roles in the diet. That is a fact that I will not deny. But I often find it comical when I hear people proclaim, “I NEED my carbs, I can’t live without them!” To many, the idea of going days without their sugar fix is like asking Lindsay Lohan to stay out of the tabloids for a week. It more than likely won’t happen. That being said, I’d like to take the opportunity to differentiate between the concept of NEED and OPTIMIZATION. Albeit briefly, because the subject alone could constitute a book in of itself.

Roughly 50-100 grams of glucose per day is needed by the brain to prevent ketosis (4). [Relax, keep reading. I know some who just read that last sentence just shit a brick and cursed my name]. Beyond that need, carbohydrates serve as a main source of fuel for energy, especially to enhance performance during high(er) intensity activity. When carbohydrates are absent or deficient in the diet, the body will enter a state called ketosis, where overall metabolism shifts from utilization of glucose for fuel to fat. The end result is the formation of ketone bodies, which are the by-product of the incomplete breakdown of free-fatty acids in the liver. Why is this relevant? Well, more than anything else, it’s a way for me to debunk the whole mantra that “the body (more specifically, the brain) NEEDS at least 50-100 grams of dietary carbohydrates per day in order to function,” that I hear being spewed out all the time.

In all actuality, the body can make all the glucose it “needs” through a process I alluded to above called gluconeogenesis (making of new glucose from non-glucose agents. When it has to, the body can make glucose from several other substances, such as glycerol, lactate, pyruvate, and amino acids (from muscle protein), to name a few. As I stated above, carbohydrates (glucose) serve as a main source of energy for the body and every tissue in the body has the capacity to use glucose. When carbohydrates are absent and the body shifts to the utilization of fat, all tissues in the body have the capacity to use fat for fuel as well……..with the exception of the brain. This is where ketones enter the picture. In a non-ketogenic state, yes, the brain utilizes around 100 grams of glucose per day (in the form of carbohydrates) to function normally. However, when dietary carbohydrates are absent, the brain can actually derive up to 75% of its energy requirements from ketones by the third week of sustained ketosis (4). So, while it’s definitely entering the world of semantics, it’s still not inherently correct to say that the body (or brain) NEEDS 100 grams of carbohydrates per day in order to function. It can get the glucose it needs from other sources as well.

Writer’s Note:
Go back and read that last section again. It took me awhile to understand the whole concept too (wink).

Now That You’re Back

The perception that all athletes (or people in general) need and should consume diets high in CHO’s needs to be dispelled as well. While it’s true that the majority of athletes do benefit from a diet that is higher in carbohydrates, it’s also true that there are a select few that do not. The amount of dietary carbohydrate that is “needed” by any one athlete/person really depends on training intensity, program design, frequency of training, and sport being played (aerobic vs. anaerobic) to name a few. Below is a chart which shows recommended carbohydrate intake for certain athletes (5).

Recommended carbohydrate intake for certain athletes

Also, do not forget the fact that the body has a limited storage capacity for dietary carbohydrates (glycogen). “In an average sized man, about 525 grams of glycogen are stored in the muscle with another 25 grams of glucose in the blood. The liver stores an additional 100 grams of glycogen, which can be broken down to glucose and released into the blood stream. The amount of energy stored as carbohydrate in the body is about 2,600 calories. This is enough energy for about two hours of moderate exercise,” (6). This is quite relevant because many studies have shown that continuous depleted muscle glycogen levels during strenuous activity, decreases performance. This is why it is crucial for many athletes (not all) to replenish glycogen stores after training on a regular basis (more on this below). This is also relevant for those who do not exercise regularly. Essentially, whatever excess carbohydrates you ingest over capacity are “spilled over” into adipose tissue and stored as fat. This is where OPTIMIZATION is key.

Insulin and Its Role In Optimization

Insulin is a hormone that is produced and secreted into the bloodstream by the pancreas, which is a glandular organ located in the abdominal cavity, behind the stomach. You have probably heard the phrase numerous times before, but it bears repeating. Insulin is a “double edged sword.” On one side, you have the VERY anabolic (muscle building) properties. The primary role of insulin is to regulate the level of sugar in the blood (when CHO’s are ingested), by shuttling glucose to muscle tissue. It not only shuttles glucose, but it also shuttles amino acids to muscle, hence why it’s considered an anabolic hormone. On the other side however, are the lipogenic (fat promoting) properties of insulin. Insulin serves as a “lock and key” in some regards. To put it simply, insulin can make you fat (by causing fat storage) and keeps you fat (by barring access to fat stores to be used for energy). Remember, insulin is a “storage hormone” and it shuttles nutrients to their respective destinations. Fat is a nutrient, and as such, is shuttled to adipose tissue. In addition, the body is going to use whatever fuel is most readily available for energy. If carbohydrates are ingested all day long and insulin is constantly elevated (not being optimized), the body’s ability to use fat for fuel is ZERO (assuming a caloric surplus of course). This helps explain why the whole “high carb, low fat” craze did not work. So as you can see, the “lock and key” analogy has quite a bit of merit. But I digress. The purpose of this section is to show you how to optimize insulin (carbohydrate intake) to take advantage of its profoundly anabolic properties. Not to throw fuel into the “carbohydrates are evil” fire.

One of these two people has learned how to optimize their carbohydrate intake. Can you guess which one?

So How the Heck Does Insulin Help Me?

Muscles need ATP to function. There is only enough ATP stored in muscle to withstand a few seconds of maximal effort, so as a result ATP needs to be replenished. Glycogen (stored glucose) it one major way to do this. It’s a well known fact that depleted muscle glycogen during strenuous activity leads to decreased performance. Such findings are relatively well known nowadays, especially if you have been reading wannabebig.com for any amount of time and/or have read the writings of Dr. John Berardi. The timing of carbohydrate consumption (and in essence glucose uptake in muscle via insulin) can have a major effect on performance and post-exercise recovery, not to mention increases in lean muscle mass.

As intensity increases, so does the body’s reliance of CHO for fuel. This is why the topic of pre and post-workout nutrition has gained a lot of notoriety in the past few years. Supplementing with CHO, either by increasing the availability of glycogen in muscle BEFORE exercise or by ingesting CHO during exercise, enhances exercise endurance (7). It has been shown that a pre-training/event meal providing an adequate supply of complex carbohydrates taken anywhere from 2-4 hours prior, can significantly improve performance.

As far as post-training, carbohydrate consumption has been highly debated amongst fitness professionals. In the end, in my opinion, it really comes down to the intensity, duration, and frequency of training. As a rule of thumb, endurance athletes typically deplete glycogen stores at a higher rate compared to non-endurance athletes. However, what can’t be debated, is the fact that numerous research has proven that:

“the rate of muscle glycogen synthesis after exercise is strongly influenced by the timing of carbohydrate ingestion (spiking insulin). Researchers led by Dr. John Ivy at the University of Texas at Austin discovered that drinking a 23% CHO solution instead of water immediately after exercising notably increased the rate of muscle glycogen synthesis above the basal rate the first two hours of recovery. It was also noted that the delay of CHO ingestion by only two hours resulted in a slower rate of glycogen re-synthesis (8).”

Again to reiterate, most research in this area has been done on endurance athletes, and because of this, I am always reluctant to simply tell people that what is found in the research applies to them. If you are in fact an endurance athlete (and sorry, walking two miles per day does not mean you are), then I would most certainly say that you should follow the protocols mentioned above. However, as far as power/strength athletes are concerned, the research is limited (albeit more IS being done as we speak), and all I can say is that it depends on your volume and intensity.

To summarize, here is a simple chart to put things into perspective on the roles insulin plays in performance:

Insulin’s Anabolic Actions – (Excerpt from Nutrient Timing, pg. 28)Metabolism of Carbohydrates

The topic of carbohydrate metabolism during exercise is confusing and to be honest, quite complicated. However, I think it’s important to know some of the general basics concerning the matter. Not to mention it will give you some great ammo for pick-up lines with the chicks. Women LOVE a man who knows his carbohydrate metabolism.

The ingestion of carbohydrates and the subsequent uptake of glucose during exercise occurs by facilitated diffusion with the help from certain transport proteins in the muscle cell; namely GLUT-4. GLUT-4 increases sarcolemmal glucose transport in response to muscle contractions during exercise and to elevated insulin after a meal. However it should be noted that exercise is a more potent stimulus for glucose uptake in skeletal muscle compared to that elicited by maximal insulin stimulation (9). This is a huge reason why I always tell people that the TIMING/optimization of their carbohydrate intake is important. Essentially, during this time, you will “use those calories and not wear them.” In the end, glucose uptake in muscle increases in proportion to exercise intensity (10). However, it should be noted that the glycogenlytic/glycolytic pathways that metabolize carbohydrate and ultimately provide “anaerobic ATP” with the production of lactate, also provide pyruvate for the oxidation of CHO and aerobic ATP production (11). In short, carbohydrate provides the substrate for BOTH aerobic and anaerobic ATP production and is why they are considered such a superb fuel source during exercise.

Aerobic Metabolism: Under oxygen rich conditions (such as a marathon), the end by-product of glycolysis (breakdown of stored glycogen) is pyruvate, which is then moved to the mitochondria of the cell to be converted to the coenzyme acetyl-CoA for entry into the Kreb’s Cycle, where it is then used to produce ATP for energy. Aerobic use of CHO yields 38-39 mmol of ATP for each mmol of glucose or glycogen consumed (12).

Anaerobic Metabolism:
Under oxygen low conditions (such as with resistance training), pyruvate is reduced to lacate and NAD in a process called oxygen independent glycolysis. Anaerobic use of CHO yields much less energy, providing only 3 mmol of ATP for each mmol of glucose derived from muscle glucogen. However, the rate of ATP provision is about twofold faster compared to aerobic metabolism (12).

Watch out ladies. ATP and GLUT-4 never seemed so hot did they?

And I Am Done

If you made it this far without falling asleep, then congratulations! Hopefully I was able to shed some light on the topic and to show you that there is more to carbohydrates then just the fact that they taste darn good. Other than learning about the different types and categories of each, I hope that I was able to shed some light and to get many of you to realize the importance of differentiating between the concepts of need and optimization. Particularly the crucial role insulin plays in the grand scheme of things as far as performance and body composition enhancement is concerned. Again, the goal of this article was to give you a reference point for the roles that carbohydrates play in the grand scheme of things. Above all, I hope it accomplished just that.

Written by Tony Gentilcore

Discuss, comment or ask a question

If you have a comment, question or would like to discuss anything raised in this article, please do so in the following discussion thread on the Wannabebig Forums – The Carbohydrate Conundrum thread.

 References

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4. McDonald, L. The Ketogenic Diet. 1998.

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6. Ivy, J., Portman, R. Nutrient Timing. North Bergen, NJ: Basic Health Publications, Inc, 2004.

7. Coyle, E.F., Coggan, A.R., Hopper, M.K., Ivy, J.L. Muscle glycogen utilization during prolonged strenuous exercise when fed carbohydrates. Journal of Applied Physiology. 61: 165-172, 1986.

8. Siff, M.C. Facts and Fallacies of Fitness (6th Ed.) Denver, CO: 2003.

9. James, D.E., Kraegen, E.W., Chisholm, D.J. Muscle glucose metabolism in exercising rats: Comparison with insulin stimulation. American Journal of Physiology. 248: E575-E580, 1985.

10. Katz, A., Broberg, S., Sahlin, K., Wahren, J. Leg glucose uptake during maximal dynamic exercise in humans. American Journal of Physiology. 251: E65-E70, 1986.

11. Spriet, I.L., Howlett, R.A., Heigenhauser, G.J.F. An enzymatic approach to lactate production in human skeletal muscle during exercise. Medicine and Science in Sports and Exercise. 32: 756-63, 2000.

12. Hargreaves, M., Spriet. Exercise Metabolism (2nd Ed.) Champaign, IL: Human Kinetics, 2006.