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Bulletin #37 – Carbohydrates: Mega Fuel For Growth And Energy

Some debate has appeared in thebodybuilding magazines recently aboutwhat’s the best dietary fuel for bodybuild-ers. Some people are advocating the high-fat diet, in which most of the day’s calo-ries are derived from fat while keepingcarbohydrate consumption to a minimum.The rationale for this approach is to avoidcarbohydrates in order to keep insulin lev-els as low as possible, thus promoting useof stored body fat as energy. This is atopic near and dear to my heart, so let’stake a close look at the facts.Let’s begin our analysis with the mostbasic concepts and move to more spe-cific considerations later. What thehigh-carb diet and the high-fat diethave in common is that they bothemphasize consuming adequate pro-tein to maintain positive nitrogenbalance.

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This is the first consider-ation of any bodybuilding diet.Many studies have documentedthat bodybuilders and enduranceathletes need a lot of protein tomake up for the loss of aminoacids which are oxidized asfuel during exercise and torepair muscle tissue which isdamaged during exercise. (See the July‘95 issue of The Parrillo PerformancePress for an extensive reference list.)Most bodybuilders do well on one gramof protein per pound of body weight perday, while others may need as much asone-and-a-half or more.

The primaryfunction of protein in the diet is to supplyamino acids which are used to supportprotein synthesis in the body. This is re-quired to repair muscles that are damagedduring exercise, to support growth of newmuscle tissue, and to allow for proteinturnover, which is the replacement of allsorts of cellular proteins that “wear out”from every day wear and tear.The rest of your daily calorie intakeis to provide energy, and this is where thetwo diets differ. One strategy is to supplymost of this energy in the form of com-plex carbs, while the other approach is tosupply the energy as fat. The truth is thateither approach can be made to work, andthe question is which one works best? Topromote the use of stored body fat asenergy the one crucial requirement whichmust be met is the body must function ina net energy deficit. This means that en-ergy consumed (dietary calories) must beless than the total amount of energy (calo-ries) the body expends. Only when yourbody burns more calories than you con-sume will it draw on stored fat for en-ergy. This is a fine line to walk, however,because if the energy deficit is too greatyou will also draw on stored protein fromskeletal muscle and internal organs forenergy.

This is why it’s important to keepprotein intake high while losing body fat,to minimize these losses. If you are fa-miliar with my program you know that Ido not advocate cutting calories to loseweight, since this slows your metabolicrate and sets into play an adaptive responsethat actually causes your body to hoardfat at the expense of protein (1,2). (Thebiochemistry and endocrinology of thiswere explained in detail in previous is-sues.) A much better way to achieve anenergy deficit is to increase your energyexpenditure by doing more aerobicexercise.You burn fat while doing theaerobics and burn more fat afterwardsbecause your metabolism has increased.So to lose body fat while maintainingmuscle mass we need to consume a dietadequate in protein and deficient in calo-ries (that is, we need to burn more calo-ries than we consume). After meeting theprotein requirement, the rest of the calo-ries can come from carbohydrates, fat,or some combination.  Just so we burnmore calories than we eat, we will losebody fat. So both diets will work, butthat’s not to say they work equally well.I believe that it is best to supply the bulkof dietary energy in the form of com-plex carbohydrates and to keep con-ventional dietary fat to a minimum.

Three general categories of reasonshave lead me in this direction: per-sonal experience with real-life body-builders, general health consider-ations, and the scientific literature.The simple truth is that the vastmajority of bodybuilders stick tothe high-carb approach becausethey have found it works bet-ter for them. Almost all of theprofessionals I’ve trained just seem to dobetter on the high-carb/low-fat diet. Be-lieve me, what matters at this level is re-sults.  If the high-fat diet gave better re-sults, that’s what I would use. But thefact is that in my experience with elite ath-letes the high-carb diet works better.That’s not some fancy technical explana-tion, it’s just the bottom line, plain andsimple.The second reason I favor the lowfat approach is for general reasons of goodhealth. The number one killer of people inthis country is heart disease, which ac-counts for as many deaths as all othercauses of death put together (includingcancer). Coronary artery disease occurswhen cholesterol plaques build up inside the arteries supplying the heart muscle,cutting off some of its blood supply (3).When the heart muscle can’t get enoughoxygen angina (chest pain) occurs.

Some-times the cholesterol plaques rupture(break), causing a blood clot to form inthe coronary artery. This completely cutsoff blood supply to part of the heart re-sulting in myocardial infarction, or a heartattack. Doctors and nutritionists all sug-gest following a low fat diet to help re-duce blood cholesterol level and preventcoronary artery disease. A diet high in con-ventional fat has also been associated withsome cancers, including breast cancer andcolon cancer (3). Furthermore, doctorsand nutritionists suggest eating a low-fatdiet to help lose weight, because gram forgram fat contains more than twice asmany calories as protein or carbohydrate,so cutting down on fat is the easiest wayto cut down on calories. So from the pointof view of general health concerns, suchas heart disease, cancer, and obesity, eat-ing a low-fat diet seems to be the way togo.Finally, there is quite a body of re-search literature supporting carbohydratesas the preferred energy source for ath-letes (see chapters 2,3, and 7 in reference4). In contrast, I don’t know of any sci-entific studies which have found conven-tional fat to be a superior energy sourcefor athletes.

As you know, weight liftingis an anaerobic activity. That means theenergy is produced without using oxygen.Carbohydrate is the body’s preferred fuelsubstrate which can be broken down toyield energy without reacting with oxy-gen. Here’s what’s going on: Let’s sayyou’re doing a set of bench presses tofailure, and you can get 8 reps with 225pounds but you fail on the ninth rep andyour training partner has to help you rackthe weight. Your pecs are working as hardas they can for about 30 seconds and thenthey give out and can’t do another rep.They fail because they run out of energyand because waste products accumulatewhich inhibit further contraction. Whilethis is happening blood is flowing to themuscle supplying it with nutrients andoxygen. The problem is the blood canonly flow so fast, so there’s a limit to howfast it can supply fuel and oxygen. Fur-thermore, it takes some time for thesechemicals to move from the bloodstreaminto muscle cells.When you go for a walk there’s noproblem supplying oxygen and fuel fastenough to keep up with the demands ofyour leg muscles. This is a low intensityexercise and you can keep it up for hoursbecause the blood flow is adequate to sup-ply the muscles with fuel and oxygen asfast as it’s being used. Weight training,on the other hand, is very intense and themuscles are performing work at the fast-est rate they can.  

This means they areconsuming energy as fast as they can—faster than can be supplied by the blood-stream.  So during a set the muscles relyon fuel already stored inside the cell. Thefirst few seconds are fueled by the phos-phate energy system, ATP and creatinephosphate. After that muscle glycogen isbroken down to pyruvate and then to lac-tic acid without reaction with oxygen. Thisbiochemical pathway is called glycolysis,and is a way for muscles to perform workfaster than would be possible if they hadto wait for oxygen to be delivered by theblood. The glycolytic pathway can sup-ply energy for a minute or two, until en-ergy substrates within the cell are depletedand waste products accumulate.The point of all this is that fat cannotbe readily used as a fuel for lifting weightsbecause fat REQUIRES oxygen to be bro-ken down (3,4). Carbohydrates are es-sentially the only fuel your body can useto lift weights, because it’s the preferredfuel the muscles can break down withoutusing oxygen (4). So right off the batthere’s a pretty good reason why body-builders should eat a high carbohydratediet. How can people on the high fat dietstill manage to lift weights?  Because theyare breaking down protein and the aminoacids are converted to glucose in the liverin a process called gluconeogenesis.

Tome it makes more sense to let dietary pro-tein be used as protein instead of beingconverted to glucose (a simple carbohy-drate) so it can be used as fuel. If yourbody requires carbs to lift weights, thenfeed it carbs. Is that so complicated?So high intensity exercise such as lift-ing weights is fueled almost exclusivelyby carbohydrates, while low intensity ex-ercise like walking or riding the station-ary bike can be fueled by carbs or fat.This is why I recommend aerobic exer-cise for bodybuilders: fat oxidation is bynecessity an aerobic activity, so this makesaerobics the best way to lose body fat. Ifyou’re going to do some aerobic exerciseactivity to burn fat, why supply fat in thediet? Would you rather be burning fat thatyou just ate or stored body fat? It makesmore sense to me to supply dietary en-ergy in the form of carbohydrates, whichcan be used as fuel for weight training,and to burn body fat to fuel my aerobicexercise. Why burn 300 calories worthof fat on the stationary bike and then turnaround and eat 300 calories worth of fatyour next meal? That just puts the sameamount of fat right back into your sys-tem. Keep in mind that fat cannot be con-verted into carbohydrate. (Technicallyspeaking, fatty acids cannot be convertedinto carbohydrate, but the glycerol back-bone can.

This only represents a few per-cent of the calories in a triglyceride mol-ecule however.) So you cannot use fat toreplenish glycogen stores.  Neither canfat be converted to protein. Dietary fatcan do two things in your body: it can be burned for energy or it can be stored asbody fat. So if you want to try the highfat diet just keep in mind that you have toburn off all those fat grams or else storethem in adipose tissue. They can’t end upanywhere else.Besides providing energy substratefor weight training, there are several otheradvantages to supplying the bulk of di-etary energy as carbohydrate instead offat. First is that excess carb calories areused to replenish glycogen stores beforethey are converted to fat. Remember, youcan convert carbs to fat, but not fat tocarbs.  If you’re on the high fat diet andconsume too many calories, the excesswill appear as body fat.  That’s the onlymetabolic fate available to it. On the otherhand, if you consume excess calories onthe high carb diet the excess carbs will beconverted to glycogen and stored in themuscles and liver. If the glycogen storesare filled up and you still have more ex-cess carb calories around, then they willbe converted to fat and stored as adiposetissue. Remember, too many calories fromany source can make you fat.

The silverlining to this black cloud is that convert-ing a carbohydrate molecule into a fat mol-ecule takes some energy. In fact, about25% of the energy in a carbohydrate mol-ecule is spent in the process of digestion,assimilation, transport, and conversion tofat. In contrast, only about 3% of the en-Carbohydrates: Mega Fuel For Growth and Energy, Part Iergy in dietary fat is used to get it fromyour mouth to your waist. Calories fromdietary fat are thus stored as body fatmuch more efficiently than are caloriesfrom carbs. Again, carbs sound like abetter deal to me.What got this debate started was theidea that by lowering carbs we couldlower insulin. Since insulin promotes fatstorage and blocks fat breakdown, thisseems like a good idea. What if I told youhow to keep insulin levels low but stillconsume a high carbohydrate diet?Sounds like the best of both worlds. Thefirst thing to do is to choose only com-plex carbohydrate sources and to avoidsimple sugars. The trick is to combine thefoods you eat at each meal so you get aslow release of carbohydrate into your sys-tem so it won’t be turned into fat. Eachmeal should contain at least one servingof  fibrous vegetables, which are digestedand released into the blood slowly. Also,by combining your carbs with protein andCapTri® you can further slow the releaseof carbs. By proper meal combining, asoutlined in the Parrillo Nutrition Manual,you can eat a diet high in complex carbo-hydrates and low in fat and still keep in-sulin at a steady, low level.  Finally, ourcarbohydrate supplement “Pro-Carb™” isspecially formulated to be slow releasing,based on a complex carbohydrate pow-der called maltodextrin.

We’ve blended 4grams of protein along with 22 grams ofcarbs into each serving, which furtherslows digestion. The product contains nosugar or artificial sweeteners. It is forti-fied with amino acids which are requiredin increased amounts during periods ofrapid growth. Pro-Carb™ is the idealsupplement to supply high quality com-plex carbohydrates in a form that digestsslowly, thus minimizing the tendency tostore as fat. Unlike the other carb drinkson the market, ours contains no sugar.Pro-Carb™ is an excellent way to supplycarbs to fuel your workouts, and worksvery well to replenish glycogen stores af-ter training. Take one or two scoops 30-60 minutes before you train and againimmediately when you finish your work-out, and see your intensity and recoveryability skyrocket. Pro-Carb™ also is anexcellent supplement to add quality calo-ries to your meals when you are trying togain muscular weight.


1. Bjorntorp P, and Brodoff BN. Obe-sity. J.B. Lippincott Co., Philadelphia,1992.

2. Remington DW, Fisher AG, andParent EA. How to Lower your Fat Ther-mostat. Vitality House International,Provo, 1983.

3. Linder MC. Nutritional Biochem-istry and Metabolism with Clinical Appli-cations. Elsevier Science Publishing Com-pany, New York, 1991.

4. Wolinsky I and Hickson JF. Nutri-tion in Exercise and Sport. CRC Press,Boca Raton, 1994.

2018-03-13T11:10:37+00:00 May 21st, 2009|Technical Supplement Bulletins|

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