A Crash Course in Diet for Athletes and Active People

Introduction

Diet is like religion. It involves individual beliefs. However, the fact remains that we are what we eat. An inadequate diet in an average, inactive person may cause:

¨      fatigue

¨      lack of resolve

¨      inability to concentrate

¨      susceptibility to illness

¨      over the long term, disease and a shortened lifespan.

However, the lifestyle of the average sedentary person requires a level of physical and intellectual performance so far below human potential, that most people are unaware of the first four symptoms and only recognise the damage caused by decades of poor dietary habits after disease or illness occur and when it is beyond repair.

For an athlete, one of the attractions of popular endurance sports like cycling, running, swimming, triathlon and cross-country skiing is that these sports awaken the participant’s awareness of his own body’s potential. However, as one hones one’s physical capabilities, the quality of the diet becomes increasingly critical. Even an athlete enrolled in the best-planned training programme will fail if his body lacks the nutrients required to grow stronger and perform better.

There is no perfect diet, just as there is no perfect training programme. Therefore, this guide seeks to educate the reader about the function and importance of different types of food and specific nutrients, and how they relate to athletic energy needs. Though this document focuses on athletes, the demands of modern life require all of us to perform at our best to be successful, so this information applies to all active people.

We hope that by using this information, readers can choose a diet that will be attuned to their individual preferences and needs, enabling them to optimise health and maximise performance in whatever they do. (Note: in this guide, we are using the pronoun “he” to represent everyone.)

I.    Sources of Energy

1.     Carbohydrates

Carbohydrates are starches or sugars. They are the primary source of energy and the preferred muscle fuel in the body. All foods must be broken down in the digestive system before they can be used as energy, but carbohydrates are far easier to break down (the process takes less time and produces less metabolic waste products) than fat or protein.

The body’s reserves of carbohydrate energy (stored in the blood, liver and muscles) are drawn on first and are rapidly depleted during exercise, which is why these are the foods athletes crave after training or competing.

Carbohydrates come in two forms; complex and simple.

Complex carbohydrates consist of long strings of glucose molecules that slowly unravel when broken down in the digestive tract. This chemical unravelling means that energy is released into the body over a long period of time, an important consideration in endurance events. The best sources of complex carbohydrates are whole-grain cereals and breads, pasta, grain products and root vegetables.

Simple carbohydrates are much smaller chemical units, and thus break down and enter the bloodstream rapidly. In small doses, simple carbohydrates give an athlete an energy lift, but when sugar enters the blood faster than it can be absorbed by the muscles, rapid chemical changes occur in the body. The result is hypoglycaemia, or low blood sugar; a condition where after rising rapidly, the blood sugar suddenly falls below the initial level, leaving less energy available to the muscles.

Eating sugary foods immediately before an endurance event may provide an initial brief surge of energy, but results in lowered energy levels towards the end of the training session or race, just when one needs it the most. Sucrose (table sugar) and glucose are the most common simple carbohydrates. Contrary to popular belief, brown sugar and honey are not significantly different from table sugar in their tendency to cause a hypoglycaemic reaction. One exception among the simple carbohydrates is fructose; it provides a quick energy lift, but because of its structure and the way it is absorbed into the body (via the liver) it does not cause the chemical changes that rapidly lower blood sugar after a short time.

Choosing carbohydrates can be tricky, since many carbohydrate-rich foods also contain large amounts of fat. Whereas carbohydrate is “fast energy” on which the muscles operate at peak efficiency, fat is slow energy, requiring more oxygen to be metabolised, and producing more waste products that the body must eliminate for peak efficiency.

Nutritional labelling allows you to compare the number of grams of carbohydrates to fats and protein and to check the ingredient list for hidden slow energy fat. Ingredients are required by law to be listed in order of their proportion in the product by weight. Products do vary; for example, some breads contain vegetable oils or even lard. Other products have no fat at all, like sourdough. Carbohydrates and protein provide 4 calories of energy per gram, while fat provides 9 calories per gram. To determine the percentage of calories from fat, multiply the number of grams of fat per serving by 9 for the total number of calories from fat. Divide this number by the total number of calories per serving to turn this number into a percentage figure.

How foods are prepared or served is important. Bread or toast are high in carbohydrates, but smearing them in butter or margarine may give them many times more fat calories than when eaten plain. Avoid fried foods. French fries may be potatoes (over 90% carbohydrates) but due to deep frying, about 50% of the calories are from fat.

2.     Fats

Some fats are necessary for health.

Besides improving the flavour of foods, they aid in digestion, are important to the health of the skin, hair and joints, and serve as the vehicle for the absorption of some vitamins.

Ironically, it is almost impossible to have a fat deficiency in the diet, since the body can produce fat from carbohydrates or protein, yet the average American diet is approximately 40% fat and the British diet is not far behind. However, a deficiency in essential fatty acids has been known to occur, but can be easily avoided if certain foods are consumed. Fat consumption, rather than overeating, is the main cause of obesity since each gram of fat has over twice the calories of protein and carbohydrates (9 calories per gram for fat versus 4 calories for carbohydrates and protein). Extra fat calories that are consumed are easily stored as fat. However, carbohydrates and protein require fairly involved chemical changes before they can be converted to fat and stored, and are thus more likely to be burned before storage can occur.

There are two kinds of fats: saturated and unsaturated. Most fats, whether from vegetable or animal sources, have a combination of the two. Saturated fats have a higher melting point, thus are more likely to be hard at room temperature and tend to harden along the walls of the arteries, causing heart disease. Unsaturated fats are more liquid and have less tendency to harden in the arteries and are thus considered healthier.

Animal fats contain cholesterol, which is a waxy substance. There are two types of cholesterol in the bloodstream, low density (LDL, or low density lipoproteins) and high density (HDL, or high density lipoproteins). High levels of LDL have been associated with heart disease, but high levels of HDL or ‘good” cholesterol are associated with resistance to heart disease. Blood cholesterol levels are affected by both heredity and diet, but it should be remembered that cholesterol is required by the human body (among other things, it keeps cell walls supple) and if insufficient cholesterol is ingested, the body will produce it. Many people equate “low cholesterol” or “no cholesterol” with “healthy”. This is overly simplistic, as foods like palm kernel or coconut oils contain no cholesterol (since they are vegetable, not animal, fats), yet they contain mostly highly saturated fats, which can be as unhealthy as animal fats, if not more so.

Since fat is slow to break down into energy and requires more oxygen than carbohydrates, endurance athletes should aim to cut down their fat intake and replace the calories with complex carbohydrates. Do this by:

·        avoiding fried foods

·        cutting down on butter or margarine smeared on foods

·        reading food labels and becoming more selective in choosing processed foods

·        choosing lower fat alternatives, e.g. frozen yoghurt has much less fat than ice cream. Some cheeses, such as mozzarella, have a lot less fat.

When using oils, those that are liquid at room temperature such as safflower, sunflower, sesame, corn and peanut are preferable to those that harden. Avoid palm kernel or coconut oils, which are hard at room temperature because of their high content of saturated fats.

Soft margarine contains less hydrogenated (processed and made saturated) oils than hard margarine, but you may prefer to use butter for superior taste. If so, simply use much less butter.

Essential fatty acids are substances found in some vegetable oils, nuts and soya beans, and are common in fish and other seafood, particularly salmon. They have roles in muscle function and energy metabolism, and have been found effective in reducing the harmful effects of an excess of other fats in the diet.

Note on Artificial Sweeteners

The preoccupation with weight loss in our society has led to millions of pounds being invested in research, development and promotion of low or zero calorie sweeteners, which are now used in dozens of products, ranging from baby food to breakfast cereal, soft drinks to hot chocolate mix. Though use of these sweeteners reduces the number of calories in many products, it has been suggested that they may actually lead to increased obesity by increasing the percentage of fat calories in the overall diet and diverting attention from the real culprit, fat. (For example, a fast food restaurant patron orders a burger and a diet soda. After eating, he still feels hungry and orders french fries or ice cream. The carbohydrate calories in an ordinary soda might have turned off the hunger mechanism, making the consumption of additional high-fat foods unnecessary.) As a general rule, it is calories consumed as fat that tend to make you fat, not calories consumed in sweeteners.

While some previous artificial sweeteners have been banned after being linked to cancer in laboratory animals, the new substances have been deemed “safe” by the authorities. However, many individuals have digestion problems including gas, cramping and other symptoms from consuming products containing them. Thus it is advised that endurance athletes carefully monitor their own physical reactions to using these products during training or near competitions.

3.     Protein

Proteins are the basic “building blocks” of human tissue. The human body is about 20% protein by weight. All proteins are made up of amino acids, some of which can be produced in the body from other substances. There are eight amino acids that human beings cannot synthesise, and these are known as Essential Amino Acids (EAA’s). These must be present in the diet to replace tissues that are continuously being broken down and to build new tissue during growth or training.

Protein is available in many foods. However, in order to build tissue, all eight of the EAA’s must be present in the proper proportions. Eggs and milk contain the EAA’s in proportion and can therefore be called a “complete protein”. Meats also contain complete proteins, but for athletes eating large amounts of meat, this creates problems because meat is hard to digest and usually contains a high percentage of fat along with the protein. For these or other health, moral or economic reasons, many athletes limit or eliminate meat, especially red meat, from their diets. White meats like chicken and turkey generally contain less fat than red meat. Fish is an excellent source of complete protein and most fish is also rich in essential fatty acids.

The proteins found in foods like grains, beans, nuts and seeds are incomplete, but since different foods have different strengths and weaknesses in their amino acid profiles, they can be combined to create complete proteins that are of a quality equal to egg and meat protein but with a lower fat content and a lower price than meat.

The following is a rough guide to complementary protein in four major food categories. You can reduce your need for animal proteins by being aware of these rules of protein complementarity and choosing your foods or preparing your meals accordingly.

Whole Grains         (wholemeal flour, noodles, cornmeal, oats, brown rice, bulgur, rye etc.)

Combine well with Milk Products or Legumes.

Milk Products    (whole or skimmed milk, cottage cheese, cheese, dry milk powder etc.)

Combine well with Whole Grains.

Seeds and Nuts    (peanuts, peanut butter, sunflower, sesame and pumpkin seeds, walnuts etc.)

Combine well with Legumes.

Legumes       (beans: red, kidney, Lima, pinto, white, haricot. Also peas, lentils etc.)

Combine well with Seeds and Nuts.

It must be remembered that these foods must be eaten during the same day to act as complete proteins.

II.  Vitamins

Vitamins are necessary for the functioning of the body and cannot be produced by the body. Thus they must be supplied by the diet.

All food consumed must be broken down before it can be utilised by the body, whether used to build new tissue, replace damaged tissue, or for energy. This breakdown process is accomplished by enzymes; large, keylike structures made from proteins, which are shaped to chemically “interlock” with the food in the digestive tract, allowing reactions to take place that break foods down into a usable form. Most vitamins are parts of enzymes or help bring enzymes together with the substances they transform.

Vitamins are vital linkages in metabolism. Without them, even a diet that includes all the needed protein, carbohydrates and fats will not maintain health, since the foods will not be utilised where and when they are needed.

When thinking about diet for the endurance athlete, there are two things to remember. First, the demands of training and competing mean that large amounts of energy are consumed, along with a constant breakdown and rebuilding of muscle and connective tissues. These processes require more food intake and thus more vitamins to facilitate the breakdown and absorption of nutrients. Secondly, while vitamins are not destroyed in the food breakdown process itself, some vitamins are water-soluble. These can be washed out of the body in urine or through sweating. Such vitamins cannot be stored in the body for long, and since athletes consume large amounts of water, water-soluble vitamins are easily washed out and thus must be present in the diet every day.

Other vitamins are fat-soluble and can be stored in the organs and fatty tissues of the body. Though these substances are still important, athletes are less likely to be deficient in these vitamins.

Vitamin deficiencies may show up in many ways. Symptoms may include rashes, sores, dizziness, anxiety, simple fatigue, susceptibility to infections or viruses, or diminished athletic performance. The following are some notes on the individual vitamins and how their function relates to training or competition. (Asterisks * indicate substances of major importance to athletes.)

Vitamin A is fat soluble, and primarily active in the cells that cover the inner and outer surfaces of the body: skin, membranes lining the mouth, respiratory passages, digestive and urinary tracts etc. Primary sources of vitamin A include dark, leafy green vegetables like spinach, broccoli and lettuce, and plants that have a rich yellow-orange colour such as carrots, squash and peaches. Vitamin A is highly concentrated in organ meats, particularly liver, and in some seafoods. If a high-potency vitamin A supplement (or multivitamin) is taken daily along with regular servings of liver and fish, then vitamin A can become toxic. However, toxicity is nearly impossible from vegetable sources.

* Vitamin B The B-complex vitamins are essential for the utilisation of energy, thus are of major importance for the endurance athlete. The "burning" of food for energy is a highly complex process. In order for the energy to be usable, the “fire” is regulated through a series of reactions which happen quickly, but must be in sequence. The B vitamins control many of these steps and the need for B vitamins increases as energy output increases. These vitamins are especially important in the breakdown of carbohydrates.

There are a number of different substances included as B vitamins, but all are necessary for energy metabolism. Fatigue will occur if the diet is deficient in even one of these vitamins. Ingesting just one B vitamin (as in a supplement pill) can upset the general balance and make a deficiency in others more severe; therefore supplementation should be balanced to include the entire family of B vitamins (as in a B-complex supplement).

The following are the individual B-complex vitamins and their functions and sources:

* Thiamine (B1) is required for release of energy from carbohydrates, protein and fats. This vitamin is often called the “Morale Vitamin”. Mild deficiencies of thiamine reduce stamina, causing depression, irritability, inability to concentrate, and chronic fatigue. The need for thiamine increases with energy output (i.e. when increasing quality or quantity of training!) It is water-soluble and not easily stored in the body. Sources of thiamine (in order of potency) include brewer’s yeast, torula yeast, oat bran, rice bran, wheat bran, beans, oats, wholemeal flour and bread, seeds and nuts, spinach and oranges.

* Riboflavin (B2) is necessary for energy release and protein synthesis (building and rebuilding tissue). Symptoms of riboflavin deficiency include soreness, cracking at the corners of the mouth, swollen membranes in mouth and throat and itchy eyes. Sources of this vitamin include cottage cheese, milk, milk products, yeast, asparagus, spinach, mushrooms and broccoli.

* Niacin (B3) is essential in the metabolism of carbohydrate, protein and fat for energy. Niacin deficiency shows up in skin rashes, nervous irritability, headaches and digestive disorders. Sources of this vitamin include soya beans, tofu, beans, cottage cheese, whole wheat, peanuts, potato, and sesame and sunflower seeds.

* Pantothenic Acid (B5) is found in every cell of living tissue. It is necessary for the breakdown of food into energy and for synthesis of tissue. Sources of vitamin B5 include whole grains, legumes (beans and peas) and yeast.

* Pyridoxine (B6) is essential in the synthesis of non-essential amino acids and protein metabolism. Also, it is vital for conversion of glucose to glycogen to provide energy to muscle tissues. Vitamin B6 is required for the production of red blood cells. Symptoms of vitamin B6 deficiency include fatigue, lack of energy and poor stamina. Sources include various beans (soya, pinto, kidney, lentils etc.), whole grains (oats, wheat, rice etc.), spinach, bananas and potatoes.

* Cobalamin (B12) is essential for the functioning of most body cells and the production of red blood cells. Sources include milk products, eggs and meat.

* Folacin, a group of important compounds necessary for the formation of RNA and DNA, works with vitamin B12 to aid in the production of new cells. Folacin sources include dark green leafy vegetables, beans, nuts, fresh oranges and whole wheat products.

* Biotin works with amino acids to transport carbon dioxide and to release energy from glucose. Sources of biotin include whole grains, vegetables and legumes.

* Vitamin C is one of the most reactive vitamins and also one of the most versatile in the body. It is necessary for the formation of collagen, which is the substance that binds the body together and forms connective tissue. Infections decrease the amount of vitamin C stores; thus it is apparently used to combat infections. It also has an important role in aiding the absorption of other vitamins and minerals. Symptoms of vitamin C deficiency include bleeding gums, listlessness, joint pains and poor endurance. Vitamin C sources are fresh fruits, especially citrus fruits, and many vegetables. Vitamin C is easily destroyed by cooking, alkalinity and oxygen.

Vitamin D functions to regulate the metabolism of calcium and phosphorus, building and maintaining strong bones and joints. Sources of vitamin D include milk and eggs. This vitamin is seldom deficient in athletes, since it is also produced by the body from sunlight reacting on skin oils.

Vitamin E aids in healthy skin and hair and seems to delay or reduce the aging process by reducing the oxidation of fats in body tissue. Some studies have claimed that vitamin E increases endurance, but these results have not been duplicated when the studies are repeated. Vitamin E is naturally present in unsaturated oils, where it prevents rancid decomposition (oxidation). Sources of this vitamin include vegetable oils, nuts, seeds, whole grains and some vegetables.

III. Minerals

Minerals have many functions in the body. Similar to vitamins, their quantity is small, but their significance in maintaining health is very important. Minerals are found as components of enzymes and hormones, as well as in the structure of tissues, especially hard tissues like bones and teeth.

As mentioned earlier, every natural element is found in some quantity in the human body, though the function of many is known, and some minerals may not have a function at all, but merely be there because they are in food and water. The six most common minerals in the body are discussed below, along with some of the “trace” minerals which are of special importance to endurance athletes. (Important minerals for endurance are denoted with *.)

* Calcium and * Phosphorus are the most abundant minerals in the body. Their main function is to keep bones and teeth hard and strong. Adequate calcium levels are also required for efficient muscular contraction, including that of the heart, and for efficient blood clotting and nerve function. Phosphorus is involved in cell growth and repair, kidney function and the utilisation of vitamins, as well as heart, nerve and muscular activity. These minerals require vitamin D to be present for absorption. Sources of calcium and phosphorus include milk, milk powder, whole grains, beans and vegetables.

Sodium, * Potassium and Chloride are the major electrolytes in the body. When dissolved in water, these minerals separate into ions that can conduct electrical charges. These electrolyte-rich body fluids either surround cells (extracellular fluids) or are contained within cell walls (intracellular fluids). Without sufficient amounts of electrolytes in these fluids, normal nerve and muscular cell function cannot take place. Electrolytes are also important in maintaining the fluid balance in the body and in the maintenance of normal pH (acid-alkalinity balance).

Since these minerals are water-soluble, they are easily washed out of the body through urination and sweat, especially during heavy exercise. The average diet contains adequate amounts of these minerals and many Westerners consume too much sodium chloride (table salt), which can cause elevated blood pressure; thus many doctors advocate salt-reduced diets. However, the serious endurance athlete can lose very large amounts of these minerals, especially during warm weather, and concern should be focused on balancing the intake of sodium chloride intake with potassium, rather than cutting out all salt. Potassium is much less prevalent in common foods. Symptoms of electrolyte deficiency include muscle cramps, fatigue, dizziness leading to impaired performance, and possibly heat prostration. Sodium chloride sources are readily available in salt or salted foods. Potassium is found in fruits, especially melon, papaya, bananas, raisins, prunes, beans, molasses, potatoes and milk. “Lo Salt” is a product which tastes and measures like ordinary salt, but contains 65% potassium chloride and 35% sodium chloride and provides a convenient way to help balance potassium intake.

Magnesium is present throughout the body and is an important activator of enzymes, especially those involved in the transfer of energy. It is required for protein synthesis (building tissue), contraction of muscles and the conduction of nerve impulses. Magnesium is water-soluble and is easily lost during heavy training. It is also often refined out of processed foods. Magnesium sources are beans, whole grains (oats, wheat, corn, rye etc.), vegetables and fruits.

Iron is essential to the enzyme systems which carry oxygen and is required for the production of haemoglobin, a protein in red blood cells which carries oxygen to the muscles. It is also found in myoglobin, the muscle protein that stores and transfers oxygen for muscle metabolism. Therefore, iron is extremely important to endurance event performance. Though iron is a trace mineral, it is the most commonly deficient nutrient in the British population. Symptoms of deficiency are pale skin, shortness of breath, general fatigue, weakness of muscles, lack of appetite and a slowing down of body processes. Iron sources include prunes, beans, spinach, peaches, raisins, molasses, tomatoes, strawberries, potatoes, oat bran and wheat bran. Vitamin C greatly increases the absorption of iron. Copper is an important mineral for growth, healing of bones, and haemoglobin and red blood cell formation. Copper sources include legumes, nuts, organ meats, seafood, raisins and molasses.

* Chromium is important in glucose metabolism and immune response. Sources of chromium are yeast, meats, cheeses and whole grains.

* Zinc is important in the growth and repair of tissues, digestion of carbohydrates and metabolism of other vitamins and minerals. Zinc is water-soluble, and thus can be lost in heavy sweating. Sources of zinc include yeast, seafood, spinach, sunflower seeds, mushrooms and meats.

IV. Fibre

For years, fibre, also known as “bulk” or “roughage”, was considered unimportant in human nutrition. However, now that research studies have suggested that dietary fibre may help protect against the development if cardiovascular disease, cancer and diabetes, fibre has become one of the hottest terms whenever nutrition is discussed. As its popularity has grown, many food manufacturers have jumped on the bandwagon, without really telling us what kind of fibre is in their products and what it really does.

Not all fibre is created equal. There are two kinds; insoluble and soluble.

Insoluble fibres such as cellulose, wheat bran or corn bran have poor water-holding capacity. They tend to speed the transit of food through the digestive tract. This can be a good thing, because it reduces the time that dietary residues, which contain micro-organisms that can produce carcinogens, stay in the system. During exercise, however, insoluble fibre can speed things up so much that diarrhoea and nausea can result. Daily intake of too much insoluble fibre from large amounts of raw fruits, vegetables and coarse cereal can also lead to deficiencies of slowly absorbed nutrients such as zinc, iron and calcium.

Soluble fibres tend to absorb water. They swell, become gelatin-like, and coat and disperse other foods so that they are assimilated slowly. As soluble fibres pass through the digestive system, they absorb and bind with bile acids which are secreted by the liver to break down fats. Since some bile acids are then eliminated, instead of being absorbed by the body, the result is less absorption of potentially harmful cholesterol and triglycerides (associated with heart disease) into the blood. Sources of soluble fibres include pectin, guar gum and oat bran. A study completed in 1984 found that eating 30 to 100 grams of oat bran (6 to 20 grams of soluble fibre) daily can actually reduce serum cholesterol and low density lipoprotein (LDL) levels in the body, while insoluble fibres like wheat bran had no effect.

V.         Individual Differences

Because of individual metabolism and body chemistry, different individuals may require more or less total food intake of individual nutrients. However, repeated nutritional studies have shown that the lack of even one of the 40 known nutrients causes disease. The human body contains at least a trace of every known natural element, though the function of many of these has not been determined.

The best way to be sure you are getting all of the needed known (and unknown) nutrients is to eat a varied diet with plenty of raw or unprocessed foods. Processing removes many of the nutrients from foods, and even enriched foods (which have had vitamins, minerals or other nutrients re-added) usually do not contain all the varied nutrients of the original product.

Remember that processing is processing, whether one is cooking at home or in a factory. Eat raw foods if possible or bake, roast, boil or steam. These methods of cooking retain most of the nutrients in food. Do not overcook, because this destroys or removes nutrients. Also, when boiling vegetables, pasta or other foods, save the liquid in which they were boiled, because the liquid contains most of the nutrients. Use this liquid in soups, when adding water to dishes such as spaghetti sauce, mixed with milk powder instead of milk in recipes, or when making bread. VI. What happens when you exercise?

In early stages of athletic activity, most energy is supplied by carbohydrates in the form of glucose. However, after several minutes, glycogen (another form of carbohydrate stored in the muscles and liver) begins to be used for energy. After a longer time period, the stores of glycogen in the muscles are reduced and the body begins to utilise additional energy from its reserves of fat. As mentioned previously, the stores of energy in the form of fat are nearly limitless, but the conversion of this fat to energy is hampered by time, the availability of oxygen to the muscles, and the buildup of waste products that occurs when fat is metabolised. Any of these factors can limit the performance of the athlete.

The more an endurance athlete trains, the more efficient his muscles become at burning fat for energy. As the athlete continues to perform, the percentage of energy obtained from carbohydrates steadily decreases; so the percentage from fat must increase. Of course many other factors, such as one's percentage of muscle tissue, the efficiency of the lungs and circulatory system in supplying oxygen, biomechanical efficiency and mental fortitude influence how good one’s athletic performance is compared to others.

As the athlete continues to exercise, the demands on the muscles for energy begin to exceed the availability of carbohydrate stores and the ability of the body to convert fat to energy. When this point is reached, usually after about an hour in a highly trained athlete (much sooner in an untrained person), the tendency is for the athlete to slow down, so that his energy output equals the availability of energy from the carbohydrate plus fat metabolism. A highly motivated, well-trained athlete who continues to push him or herself, however, is able to continue at the same level of output by drawing on protein stores. Amino acids in the blood are taken into the muscles and used for energy to fill the “gap” that forms when fat cannot be converted into energy fast enough. As the effort continues, blood amino acid levels are used up and the body turns to the most available source of protein, which is found in the major muscles that the blood is pumping through as part of the effort. This occurs after about 1¢ to 2 hours in a trained athlete. At this point, highly motivated athletes will still be able to maintain their performance, but at the price of their own body “cannibalising” their muscle. After this kind of effort, the athlete will be unable to perform at the same level for a matter of weeks or months, because it will be necessary to rebuild the cannibalised muscle through training.

The original energy drinks (like Gatorade) provide simple carbohydrates along with electrolyte minerals, while more recent refinements have begun adding complex carbohydrates for more sustained energy. The most effective approach, however, combines the consumption of high-carbohydrate starchy foods about 1½ hours before training with a drink with a high content of semi-digested starch (maltodextrin) and fructose about half an hour before training, and regular consumption of drinks high in fructose and glucose during training if the training lasts more than about 45 minutes. This minimises the degradation of muscle during training.