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Benefits of Proper Nutrition

Position of the American Dietetic Association, and the American College of Sports Medicine: Nutrition and Athletic Performance Abstract

It is the position of the American Dietetic Association, and the American College of Sports Medicine that physical activity, athletic performance, and recovery from exercise are enhanced by optimal nutrition. These organizations recommend appropriate selection of food and fluids, timing of intake, and supplement choices for optimal health and exercise performance. This position paper reviews the current scientific data related to the energy needs of athletes, assessment of body composition, strategies for weight change, the nutrient and fluid needs of athletes, special nutrient needs during training, the use of supplements and nutritional ergogenic aids, and the nutrition recommendations for vegetarian athletes. During times of high physical activity, energy and macronutrient needs — especially carbohydrate and protein intake — must be met in order to maintain body weight, replenish glycogen stores, and provide adequate protein for building and repair of tissue. Fat intake should be adequate to provide the essential fatty acids and fat-soluble vitamins, as well as to help provide adequate energy for weight maintenance.

Overall, diets should provide moderate amounts of energy from fat (20% to 25% of energy); however, there appears to be no health or performance benefit to consuming a diet containing less than 15% of energy from fat. Body weight and composition can affect exercise performance, but should not be used as the sole criterion for sports performance; daily weigh-ins are discouraged. Consuming adequate food and fluid before, during, and after exercise can help maintain blood glucose during exercise, maximize exercise performance, and improve recovery time. 

Athletes should be well-hydrated before beginning to exercise; athletes should also drink enough fluid during and after exercise to balance fluid losses. Consumption of sport drinks containing carbohydrates and electrolytes during exercise will provide fuel for the muscles, help maintain blood glucose and the thirst mechanism, and decrease the risk of dehydration or hyponatremia. Athletes will not need vitamin and mineral supplements if 
adequate energy to maintain body weight is consumed from a variety of foods. However, supplements may be required by athletes who restrict energy intake, use severe weight-loss practices, eliminate one or more food groups from their diet, or consume high-carbohydrate diets with low micronutrient density. Nutritional ergogenic aids should be used with caution, and only after careful evaluation of the product for safety, efficacy, potency, and whether or not it is a banned or illegal substance. Nutrition advice, by a qualified nutrition expert, should only be provided after carefully reviewing the athlete's health, diet, supplement and drug use, and energy requirements. 

Suggestions for food intake

• Low-energy diets will not sustain athletic training. Instead, decreases in energy intake of 10% to 20% of normal intake will lead to weight loss without the athlete feeling deprived or overly hungry. Strategies such as substituting lower-fat foods or whole-fat foods, reducing intake of energy-dense snacks, and doing activities other than eating when not hungry can be useful. 
• If appropriate, athletes can reduce fat intake but need to know that a lower-fat diet will not guarantee weight loss if a negative energy balance (reduced energy intake and increased energy expenditure) is not achieved. Fat intake should not be decreased below 15% of total energy intake, because some fat is essential for good health. 
• Emphasize increased intake of whole grains and cereals, beans, and legumes. 
• Five or more daily servings of fruits and vegetables provide nutrients and fiber. 
• Dieting athletes should not skimp on protein and need to maintain adequate calcium intakes. Accordingly, use of low-fat dairy products and lean meats, fish, and poultry is suggested. 
• A variety of fluids—especially water—should be consumed throughout the day, including before, during, and after exercise workouts. Dehydration as a means of reaching a body-weight goal is contraindicated. 
• Encourage athletes not to skip meals, especially breakfast, and not to let themselves get too hungry. They should be prepared for times when they might get hungry, including keeping nutritious snacks available for those times. 
• Athletes should not deprive themselves of favorite foods or set unrealistic dietary rules or guidelines. Instead, dietary goals should be flexible and achievable. Athletes should remember that all foods can fit into a healthful lifestyle; however, some foods are chosen less frequently. Developing lists of "good" and "bad" food is discouraged. 
• Help athletes identify their own dietary weaknesses and plan strategies for dealing with them. 
• Remind athletes that they are making lifelong dietary changes to sustain a healthful weight and optimal nutritional status rather than going on a short-term "diet" that they will someday go off.