Athlete Nutrition Timing
Athlete nutrition Timing
There has been lots of talk about Nutrition requirements especially with Macro nutrient counts, on general the western world eat WAY TOO MUCH food. our diets are all over the place from people eating less protein and more fats and carbs, “fitness” gurus are eating way too much protein.
most “athletes” aren’t aware of the nutrition timing and how important it is for your health. if you’re someone who tries to live a healthy life and play sport or even workout, then you must focus on timing of nutrition for a full recovery and so you can function to your full capacity.
● Athletes need to consume adequate energy during periods of high-intensity and/or long-duration training to maintain body weight and health and maximize training effects. Low energy intakes can result in loss of muscle mass; menstrual dysfunction; loss of or failure to gain bone density; an increased risk of fatigue, injury, and illness; and a prolonged recovery process.
● Body weight and composition should not be the sole criterion for participation in sports; daily weigh-ins are discouraged. Optimal body fat levels depend upon the sex, age, and heredity of the athlete, and may be sport-specific. Body fat assessment techniques have inherent variability and limitations. Preferably, weight loss (fat loss) should take place during the off season or begin before the competitive season and involve a qualified sports dietitian.
● Carbohydrate recommendations for athletes range from 6 to 10 g/kg (2.7 to 4.5 g/lb) body weight per day. Carbohydrates maintain blood glucose levels during exercise and replace muscle glycogen. The amount required depends upon the athlete’s total daily energy expenditure, type of sport, sex, and environmental conditions.
● Protein recommendations for endurance and strength-trained athletes range from 1.2 to 1.7 g/kg (0.5 to 0.8 g/lb) body weight per day. These recommended protein intakes can generally be met through diet alone, without the use of protein or amino acid supplements. Energy intake sufficient to maintain body weight is necessary for optimal protein use and performance.
● Fat intake should range from 20% to 35% of total energy intake. Consuming 20% of energy from fat does not benefit performance. Fat, which is a source of energy, fat-soluble vitamins, and essential fatty acids, is important in the diets of athletes. High-fat diets are not recommended for athletes.
● Athletes who restrict energy intake or use severe weight-loss practices or consume high- or low-carbohydrate diets of low micronutrient density are at greatest risk of micronutrient deficiencies. Athletes should consume diets that provide at least the Recommended Dietary Allowance (RDA) for all micronutrients.
● Dehydration (water deficit in excess of 2% to 3% body mass) decreases exercise performance; thus, adequate fluid intake before, during, and after exercise is important for health and optimal performance. The goal of drinking is to prevent dehydration from occurring during exercise and individuals should not drink in excess of sweating rate. After exercise, the athlete should drink adequate fluids to replace sweat losses during exercise, approximately 16 to 24 oz (450 to 675 mL) fluid for every pound (0.5 kg) of body weight lost during exercise.
● Before exercise, a meal or snack should provide sufficient fluid to maintain hydration, be relatively low in fat and fibre to facilitate gastric emptying and minimize gastrointestinal distress, be relatively high in carbohydrate to maximize maintenance of blood glucose, be moderate in protein, be composed of familiar foods, and be well tolerated by the athlete.
● During exercise, primary goals for nutrient consumption are to replace fluid losses and provide carbohydrates (approximately 30 to 60 g per hour) for maintenance of blood glucose levels. These nutrition guidelines are especially important for endurance events lasting longer than an hour when an athlete has not consumed adequate food or fluid before exercise, or if an athlete is exercising in an extreme environment (eg, heat, cold, or high altitude).
● After exercise, dietary goals are to provide adequate fluids, electrolytes, energy, and carbohydrates to replace muscle glycogen and ensure rapid recovery. A carbohydrate intake of 1.0 to 1.5 g/kg (0.5 to 0.7 g/lb) body weight during the first 30 minutes and again every 2 hours for 4 to 6 hours will be adequate to replace glycogen stores. Protein consumed after exercise will provide amino acids for building and repair of muscle tissue.
● In general, no vitamin and mineral supplements are required if an athlete is consuming adequate energy from a variety of foods to maintain body weight. Supplementation recommendations unrelated to exercise, such as folic acid for women of childbearing potential, should be followed. A multivitamin/mineral supplement may be appropriate if an athlete is dieting, habitually eliminating foods or food groups, is ill or recovering from injury, or has a specific micronutrient deficiency. Single-nutrient supplements may be appropriate for a specific medical or nutritional reason (eg, iron supplements to correct iron deficiency anemia).
● Vegetarian athletes may be at risk for low intakes of energy, protein, fat, and key micronutrients such as iron, calcium, vitamin D, riboflavin, zinc, and vitamin B-12. Consultation with a sports dietitian is recommended to avoid these nutrition problems.
Meeting energy needs is a nutrition priority for athletes. Optimum athletic performance is promoted by adequate energy intake. This section provides information necessary to determine energy balance for an individual. Energy balance occurs when energy intake (the sum of energy from foods, fluids, and supplement products) equals energy expenditure or the sum of energy expended as basal metabolic rate; the thermic effect of food; and the thermic effect of activity, which is the energy expended in planned physical activity and nonexercised activity thermogenesis. Spontaneous physical activity is also included in the thermic effect of activity.
Athletes need to consume enough energy to maintain appropriate weight and body composition while training for a sport (6). Although usual energy intakes for many intensely training female athletes might match those of male athletes per kilogram body weight, some female athletes may consume less energy than they expend. Low energy intake (eg, 1,800 to 2,000 kcal/day) for female athletes is a major nutritional concern because a persistent state of negative energy balance can lead to weight loss and disruption of endocrine function (7-10). Inadequate energy intake relative to energy expenditure compromises performance and negates the benefits of training. With limited energy intake, fat and lean tissue will be used for fuel by the body. Loss of lean tissue mass results in the loss of strength and endurance, as well as compromised immune, endocrine, and musculoskeletal function (11). In addition, chronically low energy intake results in poor nutrient intake, particularly of the micronutrients.
Body Composition and Sports Performance
Body fat percentage of athletes varies depending on the sex of the athlete and the sport. The estimated minimal level of body fat compatible with health is 5% for men and 12% for women (22); however, optimal body fat percentages for an individual athlete may be much higher than these minimums and should be determined on an individual basis. The International Society for Advances in Ki anthropometry sum of seven skinfolds indicates that the range of values for the athletic population is 30 to 60 mm for men and 40 to 90 mm for women. Body composition analysis should not be used as a criterion for selection of athletes for athletic teams. Weight management interventions should be thoughtfully designed to avoid detrimental outcomes with specific regard for performance, as well as body composition (ie, loss of lean body mass). See Figure 3 for practical guidelines for weight management of athletes.
MACRONUTRIENT REQUIREMENTS FOR EXERCISE
Athletes do not need a diet substantially different from that recommended in the 2005 Dietary Guidelines (16) and Eating Well with Canada’s Food Guide (28). Although high-carbohydrate diets (more than 60% of energy intake) have been advocated in the past, caution is recommended in using specific percentages as a basis for meal plans for athletes. For example, when energy intake is 4,000 to 5,000 kcal/day, even a diet containing 50% of energy from carbohydrate will provide 500 to 600 g carbohydrate (or approximately 7 to 8 g/kg [3.2 to 3.6 g/lb] for a 70-kg [154 lb] athlete), an amount sufficient to maintain muscle glycogen stores from day to day (29). Similarly, if protein intake for this plan was 10% of energy intake, absolute protein intake (100 to 125 g/day) could exceed the recommended protein intake for athletes (1.2 to 1.7 g/kg/day or 84 to 119 g in a 70-kg athlete). Conversely, when energy intake is less than 2,000 kcal/day, a diet providing 60% of energy from carbohydrate may not be sufficient to maintain optimal carbohydrate stores (4 to 5 g/kg or 1.8 to 2.3 g/lb) in a 60-kg (132 lb) athlete.
Protein metabolism during and following exercise is affected by sex, age, intensity, duration, and type of exercise, energy intake, and carbohydrate availability. More detailed reviews of these factors and their relationship to protein metabolism and needs of active individuals can be found elsewhere (30,31). The current RDA is 0.8 g/kg body weight and the Acceptable Macronutrient Distribution Range for protein intake for adults older than age 18 years is 10% to 35% of total energy (15). Because there is not a strong body of evidence documenting that additional dietary protein is needed by healthy adults who undertake endurance or resistance exercise, the current Dietary Reference Intakes for protein and amino acids does not specifically recognize the unique needs of routinely active individuals and competitive athletes. However, recommending protein intakes in excess of the RDA to maintain optimum physical performance is commonly done in practice.
An increase in protein oxidation during endurance exercise, coupled with nitrogen balance studies, provides the basis for recommending increased protein intakes for recovery from intense endurance training (32). Nitrogen balance studies suggest that dietary protein intake necessary to support nitrogen balance in endurance athletes ranges from 1.2 to 1.4 g/kg/day (29-31). These recommendations remain unchanged even though recent studies have shown that protein turnover may become more efficient in response to endurance exercise training (29,32). Ultra endurance athletes who engage in continuous activity for several hours or consecutive days of intermittent exercise should also consume protein at, or slightly above 1.2 to 1.4 g/kg/ day (32). Energy balance, or the consumption of adequate energy, particularly carbohydrates, to meet those expended, is important to protein metabolism so that amino acids are spared for protein synthesis and not oxidized to assist in meeting energy needs (33,34). In addition, discussion continues as to whether sex differences in protein-related metabolic responses to exercise exist (35,36).
Resistance exercise may necessitate protein intake in excess of the RDA, as well as that needed for endurance exercise, because additional protein, essential amino acids in particular, is needed along with sufficient energy to support muscle growth (30,31). This is particularly true in the early phase of strength training when the most significant gains in muscle size occurs. The amount of protein needed to maintain muscle mass may be lower for individuals who routinely resistance train due to more efficient protein utilization (30,31). Recommended protein intakes for strength trained athletes range from approximately 1.2 to 1.7 g/kg/day (30,32).
Fat is a necessary component of a normal diet, providing energy and essential elements of cell membranes and associated nutrients such as vitamins A, D, and E. The Acceptable Macronutrient Distribution Range for fat is 20% to 35% of energy intake (17). The 2005 Dietary Guidelines (16) and
Eating Well with Canada’s Food Guide (28) make recommendations that the proportion of energy from fatty acids be 10% saturated, 10% polyunsaturated, and 10% monounsaturated and include sources of essential fatty acids. Athletes should follow these general recommendations. Careful evaluation of studies suggesting a positive effect of consuming diets for which fat provides 70% of energy intake on athletic performance (43,44) does not support this concept (45).
Being well hydrated is an important consideration for optimal exercise performance. Because dehydration increases the risk of potentially life threatening heat injury such as heat stroke, athletes should strive for EU hydration before, during, and after exercise. Dehydration (loss of 2% body weight) can compromise aerobic exercise performance, particularly in hot weather, and may impair mental/ cognitive performance (83). The American College of Sports Medicine’s Position Stand on Exercise and Fluid Replacement (83) provides a comprehensive review of the research and recommendations for maintaining hydration before, during, and after exercise. In addition, the American College of Sports Medicine has published position stands specific to special environmental conditions (84,85). The major points from these position stands are the basis for the following recommendations.
Fluid and Electrolyte Recommendations Before Exercise.
At least 4 hours before exercise, individuals should drink about 5 to 7 mL/kg body weight (2 to 3 mL/lb) of water or a sport beverage. This would allow enough time to optimize hydration status and for excretion of any excess fluid as urine. Hyperhydration with fluids that expand the extra- and intracellular spaces (eg, water and glycerol solutions) will greatly increase the risk of having to void during competition (83) and provides no clear physiologic or performance advantage over euhydration. This practice should be discouraged
Athletes dissipate heat produced during physical activity by radiation, conduction, convection, and by vaporization of water. In hot, dry environments, evaporation accounts for more than 80% of metabolic heat loss. Sweat rates for any given activity will vary according to ambient temperature, humidity, body weight, genetics, heat acclimatization state, and metabolic efficiency. Depending on the sport and condition, sweat rates can range from as little as 0.3 to as much as 2.4 liters per hour (83). In addition to water, sweat also contains substantial but variable amounts of sodium. The average concentration of sodium in sweat approximates 1 g/L (50 mmol/L) (although concentrations vary widely). There are modest amounts of potassium and small amounts of minerals such as magnesium and chloride lost in sweat. The intent of drinking during exercise is to avert a water deficit in excess of 2% of body weight. The amount and rate of fluid replacement is dependent on an individual athlete’s sweat rate, exercise duration, and opportunities to drink (83). Readers are referred to the American College of Sports Medicine position stand for specific recommendations related to body size, sweat rates, types of work, and encouraged to individualize hydration protocols when possible (83). Routine measurement of pre and post exercise body weights will assist practitioners in determining sweat rates and customizing fluid replacement programs for individual athletes (83). Consumption of beverages containing electrolytes and carbohydrates can help sustain fluid and electrolyte balance and endurance exercise performance (83). The type, intensity, and duration of exercise and environmental conditions will alter the need for fluids and electrolytes. Fluids containing sodium and potassium help replace sweat electrolyte losses, whereas sodium stimulates thirst and fluid retention, and carbohydrates provide energy. Beverages containing 6% to 8% carbohydrate are recommended for exercise events lasting longer than 1 hour (83). Fluid balance during exercise is not always possible because maximal sweat rates exceed maximal gastric emptying rates that in turn limit fluid absorption and most often rates of fluid ingestion by athletes during exercise fall short of amounts that can be emptied from the stomach and absorbed by the gut. Gastric emptying is maximized when the amount of fluid in the stomach is high and reduced with hypertonic fluids or when carbohydrate concentration is 8%. Disturbances of fluid and electrolyte balance that can occur in athletes include dehydration, hypohydration, and hyponatremia (83). Exercise-induced dehydration develops because fluid losses that exceed fluid intake. Although some individuals begin exercise euhydrated and dehydrate over an extended duration, athletes in some sports might start training or competition in a dehydrated state because the interval between exercise sessions is inadequate for full rehydration (82). Another factor that may predispose an athlete to dehydration is making weight as a prerequisite for a specific sport or event. Hypohydration, a practice of some athletes competing in weight class sports (eg, wrestling, boxing, lightweight crew, and martial arts), can occur when athletes dehydrate themselves before beginning a competitive event. Hypohydration can develop by fluid restriction, certain exercise practices, diuretic use, or sauna exposure before an event. In addition, fluid deficits may span workouts for athletes who participate in multiple or prolonged daily sessions of exercise in the heat (84). Hyponatremia (serum sodium concentration 130 mEq/L [130 mmol/ L]) can result from prolonged, heavy sweating with failure to replace sodium, or excessive water intake. Hyponatremia is more likely to develop in novice marathoners who are not lean, run slowly, sweat less or consume excess water before, during, or after an event (83).
Skeletal muscle cramps are associated with dehydration, electrolyte deficits, and muscle fatigue. Non–heat acclimatized American football players commonly experience dehydration and muscle cramping particularly during formal preseason practice sessions in late summer. Athletes participating in tennis matches, long cycling races, late-season triathlons, soccer, and beach volleyball are also susceptible to dehydration and muscle cramping. Muscle cramps also occur in winter-sport athletes such as cross-country skiers and ice-hockey players. Muscle cramps are more common in profuse sweaters who experience large sweat sodium losses (83).
Because many athletes do not consume enough fluids during exercise to balance fluid losses, they complete their exercise session dehydrated to some extent. Given adequate time, intake of normal meals and beverages will restore hydration status by replacing fluids and electrolytes lost during exercise. Rapid and complete recovery from excessive dehydration can be accomplished by drinking at least 16 to 24 oz (450 to 675 mL) of fluid for every pound (0.5 kg) of body weight lost during exercise. Consuming rehydration beverages and salty foods at meals/snacks will help replace fluid and electrolyte losses (83).
THE TRAINING DIET
The fundamental differences between an athlete’s diet and that of the general population are that athletes require additional fluid to cover sweat losses and additional energy to fuel physical activity. As discussed earlier, it is appropriate for much of the additional energy to be supplied as carbohydrate. The proportional increase in energy requirements appears to exceed the proportional increase in needs for most other nutrients. Accordingly, as energy requirements increase, athletes should first aim to consume the maximum number of servings appropriate for their needs from carbohydrate-based food groups (ie, bread, cereals and grains, legumes, milk/alternatives, vegetables, and fruits). Energy needs for many athletes will exceed the amount of energy (kilocalories per day) in the upper range of servings for these food groups. Conversely, athletes who are small and/or have lower energy needs will need to pay greater attention to making nutrient-dense food choices to obtain adequate carbohydrate, protein, essential fats, and
micronutrients. With regard to the timing of meals and snacks, common sense dictates that food and fluid intake around workouts be determined on an individual basis with consideration for an athlete’s gastrointestinal characteristics as well as the duration and intensity of the workout. For example, an athlete might tolerate a snack consisting of milk and a sandwich 1 hour before a low-intensity workout, but would be uncomfortable if the same
meal was consumed before a very hard effort. Athletes in heavy training or doing multiple daily workouts may need to eat more than three meals and three snacks per day and should consider every possible eating occasion. These athletes should consider eating in close proximity to the end of a workout, having more than one afternoon snack, or eating a substantial snack before bed.
Eating before exercise, as opposed to exercising in the fasting state, has been shown to improve performance (89,90). The meal or snack consumed before competition or an intense workout should prepare athletes for the upcoming activity, and leave the individual neither hungry nor with undigested food in the stomach. Accordingly, the following general guidelines for meals and snacks should be used: sufficient fluid should be ingested to maintain hydration, foods should be relatively low in fat and fiber to facilitate gastric emptying and minimize gastrointestinal distress, high in carbohydrate to maintain blood glucose and maximize glycogen stores, moderate in protein, and familiar to the athlete. The size and timing of the pre-exercise meal are interrelated. Because most athletes do not like to compete on a full stomach, smaller meals should be consumed in closer proximity to the event to allow for gastric emptying, whereas larger meals can be consumed when more time is available before exercise or competition. Amounts of carbohydrate shown to enhance performance have ranged from approximately 200 to 300 g carbohydrate for meals consumed 3 to 4 hours before exercise. Studies report either no effect or beneficial effects of pre-event feeding on performance (91- 98). Data are equivocal concernin whether the glycemic index of carbohydrate in the pre-exercise meal affects performance (92,99-102). Although the above guidelines are sound and effective, the athlete’s individual needs must be emphasized. Some athletes consume and enjoy a substantial meal (eg, pancakes, juice, and scrambled eggs) 2 to 4 hours before exercise or competition; however, others may suffer severe gastrointestinal distress following such a meal and need to rely on liquid meals. Athletes should always ensure that they know what works best for themselves by experimenting with new foods and beverages during practice sessions and planning ahead to ensure they will have access to these foods at the appropriate time.
Current research supports the benefit of carbohydrate consumption in amounts typically provided in sport drinks (6% to 8%) to endurance performance in events lasting 1 hour or less (103-105), especially in athletes who exercise in the morning after an overnight fast when liver glycogen levels are decreased. Providing exogenous carbohydrate during exercise helps maintain blood glucose levels and improve performance (106). For longer events, consuming 0.7 g carbohydrate/kg body weight per hour (approximately 30 to 60 g per hour) has been shown unequivocally to extend endurance performance (107,108). Consuming carbohydrates during exercise is even more important in situations when athletes have not carbohydrate-loaded, not consumed preexercise meals, or restricted energy intake for weight loss. Carbohydrate intake should begin shortly after the onset of activity; consuming a given amount of carbohydrate as a bolus after 2 hours of exercise is not as effective as consuming the same amount at 15 to 20 minute intervals throughout the 2 hours of activity (109). The carbohydrate consumed should yield primarily glucose; fructose alone is not as effective and may cause diarrhea, although mixtures of glucose and fructose, other simple sugars and maltodextrins, appear effective (107). If the same total amount of carbohydrate and fluid is ingested, the form of carbohydrate does not seem to matter. Some athletes may prefer to use a sport drink whereas others may prefer to consume a carbohydrate snack or sports gel and consume water. As described elsewhere in this document, adequate fluid intake is also essential for maintaining endurance performance.
The timing and composition of the post competition or post exercise meal or snack depend on the length and intensity of the exercise session (eg, whether glycogen depletion occurred), and when the next intense workout will occur. For example, most athletes will finish a marathon with depleted glycogen stores, whereas glycogen depletion would be less marked following a 90-minute training run. Because athletes competing in a marathon are not likely to perform another race or hard workout the same day, the timing and composition of the post exercise meal is less critical for these athletes. Conversely, a triathlete participating in a 90-minute run in the morning and a 3-hour cycling workout in the afternoon needs to maximize recovery between training sessions. The post workout meal assumes considerable importance in meeting this goal. Timing of post-exercise carbohydrate intake affects glycogen synthesis over the short term (110). Consumption of carbohydrates within 30 minutes after exercise (1.0 to 1.5 g carbohydrate/kg at 2-hour intervals up to 6 hours is often recommended) results in higher glycogen levels post exercise than when ingestion is delayed for 2 hours (111). It is unnecessary for athletes who rest one or more days between intense training sessions to practice nutrient timing with regard to glycogen replenishment provided sufficient carbohydrates are consumed during the 24- hour period subsequent to the exercise bout (112). Nevertheless, consuming a meal or snack in close proximity to the end of exercise may be important for athletes to meet daily carbohydrate and energy goals. The type of carbohydrate consumed also affects post-exercise glycogen synthesis. When comparing simple sugars, glucose and sucrose appear equally effective when consumed at a rate of 1.0 to 1.5 g/kg body weight for 2 hours; fructose alone is less effective (113). With regard to whole foods, consumption of carbohydrate with a high glycemic index results in higher muscle glycogen levels 24 hours after glycogendepleting exercise as compared with the same amount of carbohydrates provided as foods with a low glycemic index (114). Application of these findings must be considered in conjunction with the athlete’s overall diet. When isocaloric amounts of carbohydrates or carbohydrates plus protein and fat are provided following endurance (115) or resistance exercise (116), glycogen synthesis rates are similar. Including protein in a post exercise meal may provide needed amino acids for muscle proteinepair and promote a more anabolic hormonal profile.