Mega Fuel For Growth And Energy > low carb diets
Bulletin No. 37, Mega Fuel For Growth And Energy
Parrillo Performance Products
(800) 344-3404
Some debate has appeared in the bodybuilding magazines recently about what’s the best dietary fuel for bodybuilders. Some people are advocating the high-fat diet, in which most of the day’s calories are derived 
from fat while keeping carbohydrate consumption to a minimum. The rationale for this approach is to avoid carbohydrates in order to keep insulin levels as low as possible, thus promoting use of stored body fat as energy. This is a topic near and dear to my heart, so let’s take a close look at the facts.
Let’s begin our analysis with the most basic concepts and move to more specific considerations later. What the high-carb diet and the high-fat diet have in common is that they both emphasize consuming adequate protein to maintain positive nitrogen balance. This is the first consideration of any bodybuilding diet. Many studies have documented that bodybuilders and endurance athletes need a lot of protein to make up for the loss of amino acids which are oxidized as fuel during exercise and to repair muscle tissue which is damaged during exercise. (See the July ë95 issue of The Parrillo Performance Press for an extensive reference list.) Most bodybuilders do well on one gram of protein per pound of body weight per day, while others may need as much as one-and-a-half or more. The primary function of protein in the diet is to supply amino acids which are used to support protein synthesis in the body. This is required to repair muscles that are damaged during exercise, to support growth of new muscle tissue, and to allow for protein turnover, which is the replacement of all sorts of cellular proteins that “wear out” from every day wear and tear.
The rest of your daily calorie intake is to provide energy, and this is where the two diets differ. One strategy is to supply most of this energy in the form of complex carbs, while the other approach is to supply the energy as fat. The truth is that either approach can be made to work, and the question is which one works best? To promote the use of stored body fat as energy the one crucial requirement which must be met is the body must function in a net energy deficit. This means that energy consumed (dietary calories) must be less than the total amount of energy (calories) the body expends. Only when your body burns more calories than you consume will it draw on stored fat for energy. This is a fine line to walk, however, because if the energy deficit is too great you will also draw on stored protein from skeletal muscle and internal organs for energy. This is why it’s important to keep protein intake high while losing body fat, to minimize these losses. If you are familiar with my program you know that I do not advocate cutting calories to lose weight, since this slows your metabolic rate and sets into play an adaptive response that actually causes your body to hoard fat at the expense of protein (1,2). (The biochemistry and endocrinology of this were explained in detail in previous issues.) A much better way to achieve an energy deficit is to increase your energy expenditure by doing more aerobic exercise.You burn fat while doing the aerobics and burn more fat afterwards because your metabolism has increased.
So to lose body fat while maintaining muscle mass we need to consume a diet adequate in protein and deficient in calories (that is, we need to burn more calories than we consume). After meeting the protein requirement, 
the rest of the calories can come from carbohydrates, fat, or some combination. Just so we burn more calories than we eat, we will lose body fat. So both diets will work, but that’s not to say they work equally well. I believe that it is best to supply the bulk of dietary energy in the form of complex carbohydrates and to keep conventional dietary fat to a minimum. Three general categories of reasons have lead me in this direction: personal experience with real-life bodybuilders, general health considerations, and the scientific literature. The simple truth is that the vast majority of bodybuilders stick to the high-carb approach because they have found it works better for them. Almost all of the professionals I’ve trained just seem to do better on the high-carb/low-fat diet. Believe me, what matters at this level is results. If the high-fat diet gave better results, that’s what I would use. But the fact is that in my experience with elite athletes the high-carb diet works better. That’s not some fancy technical explanation, it’s just the bottom line, plain and simple.
The second reason I favor the low fat approach is for general reasons of good health. The number one killer of people in this country is heart disease, which accounts for as many deaths as all other causes of death put together (including cancer). Coronary artery disease occurs when 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 enough oxygen angina (chest pain) occurs. Sometimes the cholesterol plaques rupture (break), causing a blood clot to form in the coronary artery. This completely cuts off blood supply to part of the heart resulting in myocardial infarction, or a heart attack. Doctors and nutritionists all suggest following a low fat diet to help reduce blood cholesterol level and prevent coronary artery disease. A diet high in conventional fat has also been associated with some cancers, including breast cancer and colon cancer (3). Furthermore, doctors and nutritionists suggest eating a low-fat diet to help lose weight, because gram for gram fat contains more than twice as many calories as protein or carbohydrate, so cutting down on fat is the easiest way to cut down on calories. So from the point of view of general health concerns, such as heart disease, cancer, and obesity, eating a low-fat diet seems to be the way to go.
Finally, there is quite a body of research literature supporting carbohydrates as the preferred energy source for athletes (see chapters 2,3, and 7 in reference 4). In contrast, I don’t know of any scientific studies which have found conventional fat to be a superior energy source for athletes. As you know, weight lifting is an anaerobic activity. That means the energy is produced without using oxygen. Carbohydrate is the body’s preferred fuel substrate which can be broken down to yield energy without reacting with oxygen. Here’s what’s going on: Let’s say you’re doing a set of bench presses to failure, and you can get 8 reps with 225 pounds but you fail on the ninth rep and your training partner has to help you rack the weight. Your pecs are working as hard as they can for about 30 seconds and then they give out and can’t do another rep. They fail because they run out of energy and because waste products accumulate which inhibit further contraction. While this is happening blood is flowing to the muscle supplying it with nutrients and oxygen. The problem is the blood can only flow so fast, so there’s a limit to how fast it can supply fuel and oxygen. Furthermore, it takes some time for these chemicals to move from the bloodstream into muscle cells.
When you go for a walk there’s no problem supplying oxygen and fuel fast enough to keep up with the demands of your leg muscles. This is a low intensity exercise and you can keep it up for hours because the blood flow is adequate to supply the muscles with fuel and oxygen as fast as it’s being used. Weight training, on the other hand, is very intense and the muscles are performing work at the fastest rate they can. This means they are consuming energy as fast as they canó faster than can be supplied by the bloodstream. So during a set the muscles rely on fuel already stored inside the cell. The first few seconds are fueled by the phosphate energy system, ATP and creatine phosphate. After that muscle glycogen is broken down to pyruvate and then to lactic acid without reaction with oxygen. This biochemical pathway is called glycolysis, and is a way for muscles to perform work faster than would be possible if they had to wait for oxygen to be delivered by the blood. The glycolytic pathway can supply energy for a minute or two, until energy substrates within the cell are depleted and waste products accumulate.
The point of all this is that fat cannot be readily used as a fuel for lifting weights because fat REQUIRES oxygen to be broken down (3,4). Carbohydrates are essentially the only fuel your body can use to lift weights, because it’s the preferred fuel the muscles can break down without using oxygen (4). So right off the bat there’s a pretty good reason why bodybuilders should eat a high carbohydrate diet. How can people on the high fat diet still manage to lift weights? Because they are breaking down protein and the amino acids are converted to glucose in the liver in a process called gluconeogenesis. To me it makes more sense to let dietary protein be used as protein instead of being converted to glucose (a simple carbohydrate) so it can be used as fuel. If your body requires carbs to lift weights, then feed it carbs. Is that so complicated?
So high intensity exercise such as lifting weights is fueled almost exclusively by carbohydrates, while low intensity exercise like walking or riding the stationary bike can be fueled by carbs or fat. This is why I recommend aerobic exercise for bodybuilders: fat oxidation is by necessity an aerobic activity, so this makes aerobics the best way to lose body fat. If you’re going to do some aerobic exercise activity to burn fat, why supply fat in the diet? Would you rather be burning fat that you just ate or stored body fat? It makes more sense to me to supply dietary energy in the form of carbohydrates, which can be used as fuel for weight training, and to burn body fat to fuel my aerobic exercise. Why burn 300 calories worth of fat on the stationary bike and then turn around and eat 300 calories worth of fat your next meal? That just puts the same amount of fat right back into your system. Keep in mind that fat cannot be converted into carbohydrate. (Technically speaking, fatty acids cannot be converted into carbohydrate, but the glycerol backbone can. This only represents a few percent of the calories in a triglyceride molecule however.) So you cannot use fat to replenish glycogen stores. Neither can fat be converted to protein. Dietary fat can do two things in your body: it can be burned for energy or it can be stored as body fat. So if you want to try the high fat diet just keep in mind that you have to burn off all those fat grams or else store them in adipose tissue. They can’t end up anywhere else.
Besides providing energy substrate for weight training, there are several other advantages to supplying the bulk of dietary energy as carbohydrate instead of fat. First is that excess carb calories are used to replenish glycogen stores before they are converted to fat. Remember, you can convert carbs to fat, but not fat to carbs. If you’re on the high fat diet and consume too many calories, the excess will appear as body fat. That’s the only metabolic fate available to it. On the other hand, if you consume excess calories on the high carb diet the excess carbs will be converted to glycogen and stored in the muscles and liver. If the glycogen stores are filled up and you still have more excess carb calories around, then they will be converted to fat and stored as adipose tissue. Remember, too many calories from any source can make you fat. The silver lining to this black cloud is that converting a carbohydrate molecule into a fat molecule takes some energy. In fact, about 25% of the energy in a carbohydrate molecule is spent in the process of digestion, assimilation, transport, and conversion to fat. In contrast, only about 3% of the energy in dietary fat is used to get it from your mouth to your waist. Calories from dietary fat are thus stored as body fat much more efficiently than are calories from carbs. Again, carbs sound like a better deal to me.
What got this debate started was the idea that by lowering carbs we could lower insulin. Since insulin promotes fat storage and blocks fat breakdown, this seems like a good idea. What if I told you how to keep insulin levels low but still consume a high carbohydrate diet? Sounds like the best of both worlds. The first thing to do is to choose only complex carbohydrate sources and to avoid simple sugars. The trick is to combine the foods you eat at each meal so you get a slow release of carbohydrate into your system so it won’t be turned into fat. Each meal should contain at least one serving of fibrous vegetables, which are digested and released into the blood slowly. Also, by combining your carbs with protein and CapTri® you can further slow the release of carbs. By proper meal combining, as outlined in the Parrillo Nutrition Manual, you can eat a diet high in complex carbohydrates and low in fat and still keep insulin at a steady, low level. Finally, our carbohydrate supplement “Pro-Carb” is specially formulated to be slow releasing, based on a complex carbohydrate powder called maltodextrin. We’ve blended 4 grams of protein along with 22 grams of carbs into each serving, which further slows digestion. The product contains no sugar or artificial sweeteners. It is fortified with amino acids which are required in increased amounts during periods of rapid growth. Pro-Carb is the ideal supplement to supply high quality complex carbohydrates in a form that digests slowly, thus minimizing the tendency to store as fat. Unlike the other carb drinks on the market, ours contains no sugar. Pro-Carb is an excellent way to supply carbs to fuel your workouts, and works very well to replenish glycogen stores after training. Take one or two scoops 30-60 minutes before you train and again immediately when you finish your workout, and see your intensity and recovery ability skyrocket. Pro-Carb also is an excellent supplement to add quality calories to your meals when you are trying to gain muscular weight.
Parrillo Performance Products
(800) 344-3404
References
1. Bjorntorp P, and Brodoff BN. Obesity. J.B. Lippincott Co., Philadelphia, 1992.
2. Remington DW, Fisher AG, and Parent EA. How to Lower your Fat Thermostat. Vitality House International, Provo, 1983.
3. Linder MC. Nutritional Biochemistry and Metabolism with Clinical Applications. Elsevier Science Publishing Company, New York, 1991.
4. Wolinsky I and Hickson JF. Nutrition in Exercise and Sport. CRC Press, Boca Raton, 1994.
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