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Bulletin #128 – Clearing Up The Confusion Over Carbs

The “low-carb revolution” we’re living in would have you believe that all carbs are bad. Not so especially for bodybuilders, athletes, and anyone who exercises regu-larly, with even a fair degree of intensity. I think we’ve lost sight of the importance of carbs for building muscle and maintaining high energy for high-performance train-ing. That’s why I’d like to set the record straight on carbs and which ones are best for bodybuilding and strength training in general .A Carb Primer For perspective, carbohydrates are grouped into two general classes: complex carbohydrates and simple sugars. Found in whole grains, vegetables, and fruits, complex carbohydrates are nothing more than simple sugars linked together into long chains. Your body digests the complex carbs into simple sugars and releases them into the bloodstream as glucose. In the end, then, all carbohydrates are converted into glucose before they are used.

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Based on this, you might think it would not make any dif-ference whether you get your carbs from starch or simple sugars—but it does. Available from candy, soft drinks, and other processed sugary foods, simple sug-ars are released into the bloodstream im-mediately, causing a rapid increase in blood sugar level and an insulin surge. Because simple sugars are released faster than the body can burn them for energy or store them as glycogen, insulin causes the excess to be converted to fat. Complex carbs, on the other hand, must be digested, a process that slows down their rate of release into the bloodstream, resulting in a more mod-erate insulin release and a more uniform energy level. Also, since they don’t cause as big an insulin release, complex carbs are not as prone to be converted to fat. One hundred grams of sugar will have a differ-ent effect on your body than one hundred grams of starch, even though both supply 100 grams of carbohydrate. Starchy Carbs and Fibrous Carbs The Parrillo Nutrition Program fur-ther subdivides complex carbs into two classes: starchy carbs and fibrous carbs.

Good sources of starchy carbohydrates are potatoes, rice, beans, oatmeal, and whole grains, and good sources of fibrous carbs include broccoli, lettuce, spinach, green beans, asparagus, and other fresh vegeta-bles. On my nutrition plan, you eat at least one to two servings of starchy carbs and one to two servings of fibrous carbs at each meal, along with a lean protein source. High fiber foods such as fibrous carbs contain cellulose, a plant carbohydrate that humans cannot digest. Cellulose, provides bulk, which helps with elimination and is good for your intestines. Also, fiber and protein slow the digestion of starchy carbs, resulting in a more gradual release of glucose into the bloodstream and more sustained energy levels. This way, insulin release is more moderate, rather than the sharp spike of insulin released in response to simple sugars . Be sure to avoid simple sugars. These include not only processed sugar but also foods like honey, milk, and fruit. Milk contains lactose, or milk sugar.

Fruit con-tains a simple sugar known as fructose, which is easily converted to fat in the liver. Although fresh fruit and low fat dairy prod-ucts are healthy, nutritious foods, they con-tain a lot of natural sugars which are easily converted into body fat. So if you’re striv-ing for ultimate leanness and a high energy level, avoid the consumption of sugary foods, including fruit and dairy products. The Body’s Optimum Energy Source Many experiments indicate that car-bohydrate is the body’s preferred fuel dur-ing exercise. More than 99 percent of the carbohydrate is used in the body to form adenosine triphosphate, or ATP, the fuel source used directly by the muscles to power contractions. ATP is not stored by the body so it must be constantly produced from the aerobic metabolism of carbohy-drates, fatty acids, and amino acids (aerobic means “with oxygen”). Carbohydrate is unique in that it can also be metabolized anaerobically (without oxygen). The anaer-obic production of ATP from carbohydrate is called glycolysis. Glycolysis makes a big contribution to the energy expended during very intense exercise of short dura-tion, such as weight lifting.

Lifting weights requires so much energy so fast that aerobic metabolism can’t keep up with the demand. By the time oxygen can get from the lungs to the muscles and inside the cells, your set is already over. Although glycolysis is rela-tively inefficient, it offers the advantage of generating energy instantly upon demand . One disadvantage of anaerobic me-tabolism is that it produces lactic acid as a waste product. Lactic acid accumulates in the muscles and the blood and is respon-sible for the burning sensation at the end of the set. The accumulation of lactic acid shuts down energy production and forces you to stop and rest. Most of the lactic acid makes its way from the muscles into the bloodstream. The liver is able to convert the lactic acid back into glucose so it can be used as fuel again. The conversion of lactic acid back into glucose requires oxygen, and this is why you continue to breathe hard for a few minutes while you’re recovering after a set. This pay-back from anaerobic metabolism is called “oxygen dept.” How Your Body Stores and Uses Carbs Your body can store only about 600 grams of glycogen (the body’s storage form of carbohydrate), although this probably varies according to your training state, diet, and amount of muscle mass.

Glycogen is stored mostly in the muscles where it will be used, and also to a small extent in the liver. Muscle glycogen is not released into the bloodstream and is only used by the muscle in which it’s stored. After muscle glycogen stores become depleted, liver glycogen is broken into glucose units and released into the bloodstream for use by working muscles throughout the body and by the central nervous system. Your muscle glycogen reserves be-come progressively lower during exercise. During long bouts of exercise, glycogen reserves may drop to critically low levels to the point of glycogen depletion. You then feel exhausted and must stop exercis-ing or dramatically reduce the intensity . The point of muscular fatigue coincides with glycogen depletion. This is separate from momentary muscular failure at the end of a set which is due to lactic acid ac-cumulation. Glycogen reserves can also be depleted gradually over a period of days if carbohydrate intake does not match that utilized during exercise. This feeling of fatigue from failure to adequately replenish glycogen reserves is often interpreted as overtraining. In some cases, overtraining may be alleviated by increased carbohy-drate consumption. Not getting a good pump in the gym is a clue that you’re prob-ably glycogen deficient.

Carbs and Training Intensity The amount of carbohydrates you take in affects your training intensity. In one study, a group of athletes consuming 300 to 350 grams of carbohydrate per day was seen to become progressively more glycogen depleted during successive days of training (1). After several days, these athletes were unable to continue with heavy training. In contrast, a diet providing 500 to 600 grams carbohydrate per day was found to elicit a complete repletion of glycogen reserves, and athletes on this diet were able to maintain a heavy training schedule. Of course, these numbers are not pre-scriptive. An individual athlete’s carbohy-drate requirement depends on his energy needs, which in turn depend on the type, in-tensity, duration, and frequency of exercise. Endurance athletes require the most energy and the most carbohydrates.

The longer and harder you train, the more carbohydrate calories you need . Some athletes train so heavily that they have trouble consuming enough high car-bohydrate foods to fuel their activities and replenish glycogen stores . Also, consuming a huge volume of food can cause gastro-intestinal distress, bloating, or discomfort, and is not conducive to optimal exercise performance. Carbohydrate drinks such as Parrillo ProCarb™ are very useful in this situ-ation, as well as for athletes trying to further increase caloric intake. ProCarb™ is also useful during training and athletic competitions to help maintain energy . This supplement contains slow-release starches (dextrins), rather than simple sugars such as glucose, sucrose, or fructose. Generally speaking, the more carbs you eat, the more carbs your body will burn for energy, and the more fat you eat, the more fat you’ll store. This is why athletes—and especially bodybuilders—should eat a diet high in complex carbohydrates and low in fat, In fact, anyone interested in having a lean, high-energy body should consume a high-carbohydrate, low-fat diet.


Costill DL, Bowers R, Branam G, Sparks K. 1977. Muscle glycogen utilization dur-ing prolonged exercise on successive days. Journal of Applied Physiology 31: 834-838 .

2018-03-13T11:10:25-04:00 July 22nd, 2009|Technical Supplement Bulletins|

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