Nutrition for Athletes

Quick Facts:

  • Athletes achieve peak performance by training and eating a balanced diet.
  • Carbohydrates and fat provide fuel for the body.
  • The use of fat as a fuel source depends on the intensity and duration of the exercise as well as the condition of the athlete.
  • Exercise may increase the athlete’s need for protein.
  • Water is a critical nutrient for athletes. Dehydration can cause muscle cramping and fatigue.
  • B vitamins are essential for producing energy from food and iron is needed to carry oxygen through the body. These are especially important for endurance athletes, athletes between 13 and 19 years old and female athletes. If adequate levels are not received through a balanced diet, taking vitamin and mineral supplements may be advised but ALWAYS consult your physician before taking any supplements.

Becoming an elite athlete requires good training and conditioning and a sensible diet. Optimal nutrition is essential for peak performance. Nutritional misinformation can do as much harm to the ambitious athlete as good nutrition can help. An individual involved in a general fitness regimen (ex. 30-40 min/day, on most days of the week) can meet their nutritional needs by adhering to a balanced diet. However, athletes involved in moderate or high frequency training program will need to increase their intake to meet nutritional requirements.


Carbohydrates are an important fuel source. In the early stages of moderate exercise carbohydrates provide 40-50% of the energy requirement. As work intensity increases carbohydrate utilization increases. Carbohydrates yield more energy per unit of oxygen consumed than fats. Because oxygen often is the limiting factor in long duration and high intensity events it is beneficial for the athlete to use the energy source requiring the least amount of oxygen per kilocalorie produced. Depending on the intensity, duration and frequency of exercise, most athletes should consume between 6-10 grams of carbohydrates per kilogram of body weight per day (a kilogram is 2.2 pounds). Carbohydrate requirements are also affected by the athlete’s sex and body mass as well as total daily energy expenditures.

Complex carbohydrates come from foods such as potatoes, beans, vegetables, whole grain pasta, cereals and other grain products. Simple carbohydrates are found in foods such as fruits, milk, honey and sugar. During digestion, the body breaks down carbohydrates to glucose which is then utilized for energy or converted to glycogen and stored in the muscles and liver to fulfill later energy needs.

During exercise, stored glycogen is converted back to glucose and used for energy. The body can only store a finite amount of carbohydrates as glycogen. The ability to sustain prolonged vigorous exercise is directly related to initial levels of muscle glycogen. For events lasting less than two hours, the glycogen stores in muscles are typically sufficient to supply the needed energy. Extra carbohydrates will not help any more than adding gas to a half-full tank will make the car go faster.

For events that require heavy work for more than two hours, a high-carbohydrate diet eaten for two to three days before the event allows glycogen storage spaces to be filled. Endurance athletes, such as long distance runners, cyclists, swimmers and rowers benefit from a pre-competition diet in which 70% of the calories come from carbohydrates. For continuous activities of three to four hours, it is important that glycogen stores in the muscles and liver are at a maximum.

Research has demonstrated that endurance athletes on a high-carbohydrate diet can exercise longer than athletes eating a low-carbohydrate, high-fat diet. However, constantly eating a high-carbohydrate diet is not advised. This conditions the body to use only carbohydrates for fuel and not the fatty acids derived from fats.

Sports drinks can be used to supply sodium and glucose if the athlete tolerates them, but other electrolytes are not essential until after the event. Athletes should experiment during training to find if electrolyte beverages are right for them.


Fat is also a significant contributor to energy needs supplying 9 kilocalories of energy per gram of fat. Using fat as fuel depends on the event’s duration and the athlete’s condition. As duration increases and/or intensity decreases, the utilization of fat as an energy source increases. For moderate exercise, about half of the total energy expenditure is derived from free fatty acid metabolism. If the event lasts more than an hour, the body may use mostly fats for energy. Furthermore, trained athletes use fat for energy more quickly than untrained athletes.

Fat consumption should be a minimum of 20 percent of total energy intake to preserve athletic performance. Maintaining adequate fat intake is crucial to meeting nutritional needs of essential fatty acids and fat-soluble vitamins including A, D, E and K.


When compared to fat and carbohydrates, protein contributes minimally to energy needs for the body. Dietary protein is digested into amino acids, which are used as the building blocks for the different tissues, enzymes, and hormones that the body needs to function. It is important for muscle building and repair that occurs after exercise.

The current Recommended Daily Allowance (RDA) for protein is 0.8 grams per kilogram of body weight per day. However, the Academy for Nutrition and Dietetics and the American College of Sports Medicine recommend that endurance athletes eat between 1.2-1.4 grams of protein per kilogram of body weight per day.

Eating protein after an athletic event has been shown to support muscle protein synthesis. However, eating protein in excess of nutritional needs has not been shown to further increase muscle building. Extra protein is broken down for energy or is stored as fat.

A balanced diet should provide enough protein as caloric intake increases. Vegetarian athletes should work with a dietitian to make sure their protein intake is sufficient. Be careful not to overdo protein intake as excess amounts can deprive the athlete of more efficient fuel sources and can lead to dehydration. High-protein diets increase the water requirement necessary to eliminate the nitrogen through the urine and can increase oxygen consumption.

Protein and amino acid supplements are generally unnecessary and not recommended unless part of a vegetarian diet set by a dietitian. Eating whole foods instead of supplements is generally the best practice. Any athlete consuming supplements in replacement of meals should consult with their doctor or a registered dietitian.


Water is an important nutrient for the athlete. Water loss during an athletic event varies between individuals. Sweat loss can be tracked by measuring weight immediately before and after exercise. After exercise 16-24 oz of water should be consumed for every pound that was lost during the athletic event. By routinely tracking pre- and post- exercise weight changes, sweat rates can be estimated, allowing for more efficient hydration during athletic events.

To avoid dehydration, an athlete should drink 5 to 7 mL per kilogram of body mass approximately four hours before an event. Throughout the event, they should drink chilled water or electrolyte drinks, consuming enough to match sweat losses. Chilled fluids are absorbed faster and help lower body temperature.

It is important to account for environmental concerns when considering water consumption. Sweat rates may increase dramatically in hot and humid weather, and it is increasingly important for an athlete to stay hydrated in these conditions. Competing at high altitudes also increases water needs.

Athletes consuming sport drinks or energy drinks should be aware of caffeine levels. Limited amounts of caffeine have been shown to enhance athletic performance. However, insomnia, restlessness and ringing of the ears can occur with caffeine consumption. Furthermore, caffeine acts as a diuretic and may cause the need to urinate during competition.


Maintaining adequate levels of vitamins and minerals is important for bodily function and athletic performance. As the activity level of an athlete increases the need for different vitamins and minerals may increase as well. This can typically be met by eating a balanced diet.

B vitamins, including thiamine, riboflavin and niacin, are essential for producing energy from the fuel sources in the diet. Carbohydrate and protein foods are excellent sources of these vitamins. B vitamins are water soluble vitamins – which means that are not stored in the body Some female athletes may lack riboflavin, so it is important to ensure adequate consumption of riboflavin-rich foods such as milk.

Vitamin D has many functions in the body, and is crucial for calcium absorption. Athletes who train indoors for prolonged periods of time should insure that they consuming adequate amounts of vitamin D through diet.

Exercise increases the oxidative stress on the body and increases the need for vitamins C and E – which have an antioxidant effect. Vitamin E is a fat soluble vitamin found in nuts, seeds and vegetable oils. When an individual consumes excess fat-soluble vitamins (A, D, E and K), they are stored in fat throughout the body. Because they are stored, excessive amounts of fat-soluble vitamins may have toxic effects.


Minerals play an important role in athletic function. Heavy exercise affects the body’s supply of sodium, potassium, iron and calcium.

Sodium is lost through the course of an athletic event through sweat, so it may be necessary to replace sodium in addition to water during an event.

Potassium levels can decline during exercise, similar to sodium, though losses are not as significant. Eating potassium-rich foods such as oranges, bananas and potatoes throughout training and after competition supplies necessary potassium.

Iron carries oxygen via the blood to all cells in the body. Needs for iron are especially high in endurance athletes, female athletes (due to menstruation) and athletes between the ages of 13 and 19. Choosing foods high in iron such as red meat, lentils, dark leafy greens, and fortified cereals can help prevent iron deficiencies, but taking an iron supplement may be advised. It is best to consult a physician before starting iron supplements.

Calcium is important in bone health and muscle function. Female athletes are more likely to have inadequate calcium consumption. Low-fat dairy products are a good source of calcium.

The Pre-Game Meal

Eating before competition can increase performance when compared to exercising in fasted state. A pre-game meal three to four hours before the event allows for optimal digestion and energy supply. Most authorities recommend small pre-game meals that provide 500 to 1,000 calories. This meal should be sufficient but not excessive, so as to prevent both hunger and undigested food.

The meal should be high in starch, which breaks down more easily than protein and fats. The starch should be in the form of complex carbohydrates (breads, cold cereal, pasta, fruits and vegetables). They are digested at a rate that provides consistent energy to the body and are emptied from the stomach in two to three hours.

High-sugar foods lead to a rapid rise in blood sugar, followed by a decline in blood sugar and less energy. In addition, concentrated sweets can draw fluid into the gastrointestinal tract and contribute to dehydration, cramping, nausea and diarrhea. Don’t consume any carbohydrates one and a half to two hours before an event. This may lead to premature exhaustion of glycogen stores in endurance events.

Pregame meals should be low in fat. Fat takes longer to digest, as does fiber- and lactose-containing meals.

Take in adequate fluids during this pre-game time. Avoid caffeine consumption (cola, coffee, tea) as it may lead to dehydration by increasing urine production.

Smaller meals should be consumed if less time remains before an event. If a competition is less than two hours away, athletes may benefit from consuming a liquid pre-game meal to avoid gastrointestinal distress. A liquid meal will move out of the stomach by the time a meet or match begins. Remember to include water with this meal.

The Post-Game Meal

Regardless of age, gender or sport, the post-game competition meal recommendations are the same. Following a training session or competition, a small meal eaten within thirty minutes is very beneficial. The meal should be mixed, meaning it contains carbohydrate, protein, and fat. Protein synthesis is greatest during the window of time immediately following a workout and carbohydrates will help replete diminished glycogen stores. However, consume food within the 30 minute window may be difficult for athletes—they often experience nausea or lack of hunger. One option is to consider consuming a drink that contains carbohydrates and protein. There are several liquid smoothies and beverages on the market that provide high protein and carbohydrates for replenishment. One classic is chocolate milk.

It is crucial to maintain nutritious eating not only for athletic events, but all the time. A pre-game meal or special diet for several days prior to competition cannot make up for inadequate nutrition in previous months or years. Lifelong nutrition habits must be emphasized. Combining good eating practices with a good training and conditioning program will allow any athlete to maximize their performance.