Energy represents the capacity to do work, and the human source of energy is FOOD. A calorie is the standard measure of energy. The amount of energy expended depends on the duration and type of activity.

Carbohydrates and fats are primary energy nutrients.

Protein can become a source of energy but to a limited extent. Protein is however, essential for growth and repair of muscle and body tissues.

Fat not only is important in relation to fat-soluble vitamins, but it is also essential as an energy source for low to moderate intensity exercise. Carbohydrate is the optimal energy for high intensity aerobic and anaerobic exercise. For optimal performance, an athlete should eat a calculated balance of macronutrient and micronutrients. (Macronutrients are carbohydrates, proteins and fats, and micronutrients are vitamins and minerals.) Vitamins and minerals are elements critical for chemical processes in the body and thus for normal human functioning. The fibrous indigestible portion of food, called fiber, is also essential for a healthy digestive system. Last but not least, water! Water, is essential as a vehicle for carrying other nutrients.

Calculating your Individual Energy Needs

A simplistic calculation can help determine an estimate of energy required for an athlete.

Energy required = Resting energy Expenditure (REE) (basically what your body needs just to function) + physical activity requirements.

To calculate an estimate of REE:

For every kilogram of body weight, an athlete requires approximately 1.3 calories per hour. For example:

An athlete weighing 60 Kg would require 1.3 x 24 hrs x 70 Kg = approx 1872 calories.

To calculate physical activity requirements:

For every hour of activity, 8.5 calories is required kilogram of body weight. For example: For 2 hours of training, a 60 kg athlete requires 8.5 x 2 (hours) x 60 (kg of body weight) = 1020 calories Thus an athlete weighing 60Kg, who trains for two hours, would require an intake of approx: 1870 + 1020 calories = 2890 calories (approx 3000 calories rounded up)

The Optimal Breakdown of Nutrients for Athletes

Like fuel for a car, energy from food also has an optimal blend. The blend for an athlete may depend on the type of sport s/he is involved in, however, in general: 55-60% of energy should be from carbs. Glycogen is the main source of energy used by the muscles to enable you to undertake both aerobic and anaerobic exercise. Most ingested carbohydrates are initially converted to blood glucose and used for energy or stored as glycogen, but excess may be stored as fat. Blood glucose is essential for optimal functioning of the nervous system, whereas muscle glycogen is essential for endurance exercise. Low levels of glucose or muscle glycogen may be contributing factors in the early onset of fatigue, in other words, training with low glycogen stores will result in a constant feeling of tiredness, a lowering of training performance and an increased risk for injury and illness. 25 – 30% of energy should be from fats. One of the main functions of fat is to provide energy. In general a low-fat diet is recommended for both health and physical performance. An athlete should consume less high fat meats and dairy products and more fruits, vegetables and whole grains, dietary fiber, lean meats, and nonfat dairy. 20 – 25 % of energy should be from protein. The major function of protein is to repair and build tissues and to synthesize hormones, enzymes, and other body components. Protein may be used as a source of energy under certain conditions, such as intense exercise during low carbohydrate stores. Although some athletes may benefit from additional protein, they do not need expensive commercial protein supplements, instead they should obtain the extra protein from increased caloric intake of food associated with their physical activity requirements.

The 60kg athlete would then calculate his daily requirements as follows:

In Summary

Nutrient balance is critical to good health and performance. The athlete’s goal should be to find the appropriate balance between all the nutrients, since too much or too little of any one nutrient will cause health and/or performance problems. For instance, too little iron intake would lead to poor endurance and lower ability to burn fat, while too much protein could increase urine production and increase the risk of dehydration. The best strategy for maintaining a nutrient balance is to eat a wide variety of foods, regularly consume fresh fruits and vegetables, and avoid a monotonous intake of the same few foods day after day.

The easiest way to assure optimal nutrient exposure is to consume a wide variety of foods. No single food has all the nutrients a person needs to stay healthy so eating a wide variety of foods helps people know that all the needed nutrients are available to them. An added benefit of eating a wide variety of foods is avoidance of nutrient toxicities, which result from excess vitamin and mineral intake.

Applying nutrition and hydration principles is of great benefit to optimize an athlete’s training and performance. The athletes that understand the digestion and absorption of nutrients and fluids are more likely to develop optimal methods of maintaining blood volume (a critical issue for performance), without inducing nausea and vomiting (GI Distress).

For any fluid to be of benefit during exercise, it must first empty from the stomach and then be absorbed into the bloodstream from the intestines. A number of factors influence the gastric emptying rate, including hydration status, concentration of the liquid, volume, caloric density (concentration of the fluid), temperature of the liquid as well as external temperature, and exercise intensity.

The most common causes of GI distress are thus a spin off from these influences:

Hydration status:

Recent research has shed new light onto understanding hydration. Endurance athletes attempt to offset dehydration in fear of the old myth that dehydration poses the threat of less than optimal performance. Contrary to the marketing claims made by the leading sports drink industry in the early 70’s – the need for maximum hydration is not necessary. In fact, it is not possible to drink enough to fully offset dehydration without causing a negative consequence. .An attempt to offset dehydration during intense exercise is the surest way to induce GI distress since too much fluid may result in a delayed gastric emptying response.

Furthermore, overhydration could induce a more serious condition called Hyponatremia, or water intoxication (sodium concentration of body fluids fall too low).

To overcome both the risk of GI distress or hyponatremia: drink enough fluid to slow dehydration and not necessarily prevent it. Continuous sipping  is recommended, or else hydrating with small volumes every 20 – 30 minutes, or better yet, drink according to thirst.

Concentration and type of carbohydrate of the Fluid:

The speed at which a beverage travels from the stomach in to the small intestine (the gastric emptying rate) depends on the energy content (calories) and volume of the beverage consumed. A small concentration of carbohydrate will encourage rapid absorption, but too much carbohydrate will slow gastric emptying and can result in GI distress. Sports drinks are scientifically formulated for optimal gastric emptying. Furthermore, sports drinks also aid in replenishing glycogen stores in working muscles, as well as electrolyte balancing and replenishment and are therefore valuable hydration options. The concentration and the type of carbohydrates in a sports drink however, require some consideration.

There appears to be no major difference between glucose, sucrose, maltodextrins, fructose and starch on athletic performance itself. Fructose, however, has a slower absorption rate, and in large quantities, is likely to cause GI distress than any of the other carbohydrate s. Fructose is sweeter than maltodextrins and is often used to make the drink appealing. Maltodextrins remove the unpalatable sweetness, and sucrose is absorbed more rapidly than fructose. Thus read labels carefully, look for a combination of these carbohydrates. Carbohydrates regardless of whether solid or liquid will aid in athletic performance, but consider drinking them rather than eating them, since the fluid takes care of two very important performance issues: hydration and energy.

Intensity of exercise:

Stomach and intestinal distress tend to increase during high-intensity training. Stomach fullness is also directly related to gastrointestinal discomfort levels during intense sporting activity. Different intensities also result in different carbohydrate utilization. For instance, in endurance running and intermittent stop-and-go sports, there is a reduction in the rate of muscle glycogen depletion when carb drinks are consumed, but for strenuous cycling the rate of muscle glycogen depletion has not been shown to be affected.

Keeping in mind that gastric emptying is optimal at 6 – 8% carbohydrate sports drinks, consuming these fluids regardless of activity may help maintain athletic performance and prevent over volumizing with water.

Ergogenic aids:

High doses of vitamins and minerals and some ergogenic aids, such as creatine, may cause GI distress. Creatine has recently become one of the most popular ergogenic aids marketed to athletes. Some studies have shown creatine supplementation may promote gains in strength, performance and fat-free mass which is either due to increased muscle mass or water retention. While not all studies report ergogenic benefits, most studies warn about the danger in incorrect dosing. There are also concerns about muscle cramping and increased muscle injuries and of course GI distress. Ingesting a carbohydrate drink at the same time creatine is consumed, has been shown to increase creatine accumulation in the muscle however it also increases water retention, as a result. The risk of developing GI distress is thus increased when combining sports drinks with ergogenic aids.

In Summary:
GI distress may be an individual adversary. It is important to experiment to find out which sports products work best for you.  Water is a good drink if exercising for less than one hour. Carbohydrate-electrolyte drinks, such as Gatorade, are good for endurance and high intensity training as they are absorbed at optimal rates.

Water provides no flavor or electrolytes, which cause athletes to want to drink. Beverages that cause athletes to want to drink help them stay well hydrated. Water supplies no energy while sports beverages contain carbohydrate. The carbohydrate helps athletes provide their muscles with the needed fuel to avoid early fatigue and poor performance. The sodium provided by sports beverages helps athletes maintain blood volume, a factor that is critical to maintaining sweat rates and performance. Sweat contains sodium that water alone does not replace. However, to prevent GI distress, these fluids should not be more than 6 – 8 % carbohydrate concentrated (approximately 14 grams of carbohydrate per 8 oz); they should have a mixture of sucrose, glucose and fructose; and they should provide a minimum of 100 mg sodium and 28 mg potassium per 8 oz servings.