Your body needs fuel to power its activities. During low level activity, like casual walking, fat serves as a pri-mary fuel source. As exercise intensity increases your body comes to rely more heavily on carbohydrates for its source of energy. During prolonged endurance activities such as aerobics (and especially after glycogen reserves become depleted), amino acids can contribute significantly to the fuel mix, accounting for as much as ten percent of oxidized substrate. Since most of us exercise intensely, we are de-pendent on carbohydrates for optimal performance. This is true for both body-builders and endurance athletes. Of all the ergogenic (performance enhancing) substances available, evidence suggests that carbohydrates and water work best for powering through a workout. Without these critical nutrients the body cannot generate power and perform work at the optimal level.
When endurance athletes “bonk” or “hit the wall” glycogen stores are depleted and blood sugar levels start to drop . This causes a dramatic reduction in muscular power output and causes fa-tigue of the central nervous system. The human body can store roughly 400 grams of glycogen, which is the storage form of carbohydrates. This amounts to about 1,600 calories and is not enough energy to last most of us even one day. Since we can’t store very much, it is critical to maintain an adequate supply of carbohydrates. The optimal carbohydrate intake varies from person to person, de-pending on athletic goals, body size and training pattern. Endurance athletes burn the most fuel and thus have the highest carbohydrate requirements. Bodybuilders who follow our Parrillo prescription of high intensity aerobics and weight training should consume a diet fairly high in carbo-hydrates. During the growth season, while the emphasis is on gaining lean muscle, a diet relatively higher in carbohydrates will help support weight gain. During pre-contest dieting, when the goal is fat loss, a reduction in carbohydrates works bet-ter. Carbohydrates are almost exclusively derived from plant sources.
Meat is a very poor source of carbohydrates. We divide carbohydrates into several categories. The first two are simple sugars and refined carbohydrates. Simple sugars include sugar and honey as well as fruit and fruit juice. Fruit is sweet because it contains the sugars glucose and fructose. It is advisable to avoid simple sugars and refined carbo-hydrates because they readily promote fat storage. To some extent they are converted into fat, but more importantly they cause a big insulin release from the pancreas and this blocks the use of fat as fuel. If you don’t burn any fat as fuel then it slowly accumulates. Fructose is found primarily in fruit but also in artificial sweeteners like high fructose corn syrup – which is especially bad since it is preferentially converted to fat in the liver. Examples of refined carbohydrates include bread, pasta and anything made with flour. That would include muffins and cookies, cake, crackers, pretzels and so on. Chips, even the low fat kind, will fall into this cat-egory since their carbohydrates are refined. During refining the grain which supplies the carbohydrate is pulverized and the fiber is removed. The carbohydrates are ground into a fine powder and this increases its surface area-to-mass ratio .
These factors, taken together, result in certain carbohydrates being di-gested, entering the bloodstream very rap-idly and triggering a powerful release of insulin. Refined carbohydrates behave in the body much like simple sugars and we recommend that athletes trying to get in shape avoid all simple sugars and refined carbohydrates, including sugar, fruit, fruit juice, bread and pasta. Milk is not a good bodybuilding food since it is rich in the simple sugar lactose. A glass of milk ac-tually contains more sugar than protein, something a lot of people don’t real-ize. Starches and fibrous vegetables are “good” carbohydrate sources and we en-courage our athletes to eat these . Starch is a long chain of glucose. Glucose is sugar released into the bloodstream and a primary fuel for muscles. Glucose is the storage form of carbohydrates in plants. Glycogen is very similar to starch and is the storage form of carbohydrates in animals. The difference between starch and glycogen has to do with the branch-ing pattern and starch is a good energy source that is digested slowly compared to refined carbohydrates. This results in a more favorable insulin profile for starch.
Starch is the best food source of carbohydrate for athletes. Good examples of starchy carbs include oatmeal, corn, peas, rice, beans, potatoes, sweet potatoes, lentils, legumes, and whole grains. Fibrous vegetables don’t supply many calories but are the prime sources of fiber, a critical nutrient for bodybuild-ers. Fiber slows the rate of release of glucose into the bloodstream thus helping to moderate insulin levels. Good fibrous vegetables are lettuce, spinach, aspara-gus, broccoli, cauliflower, brussel sprouts, beans (not canned), lentils, peas, turnip greens, squash, zucchini, okra, oatmeal, oat bran, All-Bran cereal or Fiber-One cereal (check to make sure these have no sugar), cabbage, celery, peppers, sweet potatoes, eggplant, cucumbers, onions and whole grain brown rice. Generally any other vegetable is acceptable. I would stay away from avocados, olives and nuts, as they are high in fat. It is important to combine foods properly when you prepare a meal. We call this “meal structuring.” Each meal should contain a protein source, a starchy carbohydrate and a fibrous vegetable.
By combining protein and fiber with your starch, and by avoiding simple sugars and refined carbohydrate, the rate of release of glucose into the bloodstream is greatly reduced. This helps keep insulin levels low which permits the continued use of fat as fuel. This style of eating encourages ingested nutrients to be stored as muscle or glycogen rather than compartmentalized in fat storage. How many carbohydrates should you eat in a day? This varies from person to person, so I can’t give you some magic number, but I can teach you how to figure it out for yourself. The first thing to con-sider is your daily caloric requirement. If you don’t already know what that is, start weighing your food and use a calorie chart to calculate how many calories you are consuming each day. The Parrillo Per-formance Nutrition Manual comes with a food scale and diet trac sheets along with detailed instructions.
Next, construct your diet so that fat is limited to 5-10% of calo-ries consumed and eat one to two grams of clean (low fat) protein per pound of body weight each day. If you’re lean and are try-ing to gain weight add more carbohydrates. If you are trying to strip off fat try eating two grams of protein per pound of body weight each day and cut back on your carb intake. Establish your daily intake of calories from fat and protein and derive the rest from quality carbohydrates. Include starchy and fibrous carbs at each meal, avoiding the other carb sources.Did you ever wonder how carbo-hydrates are metabolized in the body? The starch is broken down into glucose units inside the small intestine and absorbed into the bloodstream. From there it is carried to the liver by the portal vein. Much of it is retained in the liver where it is converted into glycogen. Once liver glycogen stores are filled to capacity the remainder of the glucose load is released into the gen-eral circulation where it is taken up by the muscles, brain, or other organs and used as fuel. As long as blood glucose levels are normal, glucose is (generally) used pref-erentially as fuel over fat or amino acids. Muscle has the ability to store glycogen, so whatever glucose is taken up by muscle – but is not needed immediately for fuel – is retained as glycogen .
Under normal conditions not much glucose is converted into fat, although this can happen during prolonged periods of over-eating. Glucose can be used as fuel or stored as glycogen by liver and muscle. Several hours after the meal, when blood glucose levels start to drop, liver glycogen is broken down and the stored glucose is released into the bloodstream. You can maintain fairly uni-form blood glucose levels without having to eat constantly .Parrillo’s Pro-Carb Powder™ and 50-50 Plus™ are both excellent sources of Carbohydrates: The Bodybuilders Best Friend or Worst Enemy?slow-release carbohydrates and ideal for both improving exercise performance and providing post-workout glycogen replace-ment. In terms of convenience it’s impos-sible to beat Parrillo Bars. Keep some in your gym bag and have one when you finish your workout to start replenishing glycogen right away. Try and get a handle on the different types of carbohydrates. Eliminate the refined carbs and those that contain sugar . Manipulate your starch and fiber intake to achieve your desired results. Keep tabs on your carbs and how much you ingest. You will be well on your way to achieving the physical goals to which you aspire .
1. Flatt JP. Dietary fat, carbohydrate bal-ance, and weight maintenance: effects of exer-cise. Am. J. Clin. Nutr. 45: 296-306, 1987.
2. Flatt JP. Use and storage of carbohydrate and fat. Am. J. Clin. Nutr. 61: 952s-959s, 1995.
3. Acheson KJ, Flatt JP, and Jequier E. Gly-cogen synthesis versus lipogenesis after a 500 gram carbohydrate meal in man. Metabolism 31: 1234-1240, 1982 .
4. Liebman M and Wilkinson JG. Carbohydrate metabolism and exercise. Chapter 2 from Nutri-tion in Exercise and Sport, edited by Wolinsky I and Hickson JF, CRC Press, Boca Raton, 1994.
5. Miller GD. Carbohydrates in ultra-endurance exercise and athletic performance. Chapter 3 from Nutrition in Exercise and Sport, edited by Wolinsky I and Hickson JF, CRC Press, Boca Raton, 1994.
6. Hargreaves M. Skeletal muscle carbohydrate metabolism during exercise. Chapter 2 fro-mExercise Metabolism, edited by Hargreaves M, Human Kinetics Publishers, Champaign, IL, 1995.
7. Coggan AR and Williams BD. Metabolic adaptations to endurance training: substrate metabolism during exercise. Chapter 6 from Exercise Metabolism, edited by Har-greaves M, Human Kinetics Publishers, Champaign, IL, 1995.