Athletes apply well-executed fuel strategies -also known as energy management- to stay at their best throughout their careers. The energy goal of a healthy athlete is to be able to adjust his dietary intake to cover all expenditures from training. These adjustments support an energy balance that is positive for health and performance. This article will shine light on what energy balance, energy availability and low energy are and the effects that may occur in athletes in such cases. In addition, it is explained how this balance can be achieved with nutrients and what can happen if it is not provided.
The first condition for optimizing training and performance through nutrition is to ensure that the athlete consumes enough calories to balance energy expenditure. Knowing the energy concepts in sports nutrition is at the beginning of performance-enhancing strategies. Energy availability can be defined as the energy the body can use after deducting the energy cost of physical activity from daily energy intake. In short, it is the amount of energy that can be spent to meet the physiological needs of the body (Maughan et al., 2012). Energy availability, which relates energy intake to the energy cost of exercise, can play a key role in the success of health and athlete nutrition strategies (Thomas et al., 2016). Low energy availability: Low energy availability occurs when an individual's dietary energy intake is insufficient to support energy expenditure necessary for health, function, and daily living, taking into account the cost of exercise and sports activities (Loucks, 2013; Loucks et. al., 2011). Relative Energy Deficiency in Sport: The syndrome of RED-S refers to impaired physiological functioning caused by relative energy deficiency, and includes but is not limited to impairments of metabolic rate, menstrual function, bone health, immunity, protein synthesis and cardiovascular health (Mountjoy et al., 2014).
Everyone has different nutritional needs, and there is no one-size-fits-all diet. Hence, the diet and needs of each person and athlete are different. The following guidelines are based on the Joint Position Statement on Nutrition and Athletic Performance from the American College of Sports Medicine, Academy of Nutrition and Dietetics and Dietitians of Canada, The International Olympic Committee Consensus Conference on Sports Nutrition and the International Associations of Athletics Federation (IAAF) Consensus Statement (Bean, 2022). Nutrition is one of the most important factors affecting performance (Maughan, 1997). Proper nutrition has been predicted to be a fundamental and vital contribution to improving every aspect of performance (Rodriguez et al., 2009). Studies have pointed out that nutritional status is a critical determinant that has a direct impact on the level of sportive performance (Singh et al., 2010; Kibata, 2011). Burke and Deakin (2010) reported that malnutrition results in poor sports performance. It is accepted [generally understood] that a balanced and adequate nutrition suitable for the athlete increases the performance of the athlete (Close et al., 2016).
The energy goal for a healthy athlete is to be able to adjust the dietary intake to meet all the expenditure from exercise and training. These adjustments support an energy balance that is positive for health and performance. Energy Balance is usually calculated over longer periods, typically days or weeks, and represents the difference between energy intake and energy expenditure. When energy intake exceeds energy expenditure, the energy balance is "positive" and will result in weight gain. When energy intake is below energy expenditure, the energy balance is "negative", resulting in weight loss. In the long run, energy balance and weight are maintained in balanced individuals, but at the daily level, this balance can be positive or negative (Jeukendrup, 2004). An energy deficit can be defined as the discrepancy in energy balance when dietary energy intake is less than total energy expenditure, energy loss from the body's energy stores, and/or compensatory mechanisms occur to reduce total energy expenditure (Loucks, 2013; Loucks et al., 2011).
Athletes can sometimes intentionally or unknowingly alter their energy availability negatively. Energy availability can be increased by increasing training, exercising excessively, or reducing the amount of food he eats. Some athletes adopt abnormal eating behaviors such as fasting, skipping meals, restricting food, overeating, or using diet pills, or laxatives. Other athletes also have eating disorders. Whatever the case, these scenarios can result in low energy availability.
Figure 1: Human metabolism vector banner. (Unknown, 2020)
Low energy availability results in complications that can cause hormonal, metabolic and functional disruptions in both the male and female body. This energy deficiency can affect physiological functions such as metabolic rate, bone health, immunity, protein synthesis, cardiovascular and psychological health, and menstrual function (De Souza et al., 2014, 2019; Mountjoy et al., 2014, 2018). It can also impair the body's ability to use glucose effectively for energy, increase fat stores in the body, increase cholesterol, slow down your metabolic rate, and decrease growth hormone production (Kleiner and Greenwood-Robinson, 2018). In addition, oftentimes physiological symptoms of low energy availability, such as menstrual dysfunction, negatively affect sports performance in female athletes (Vanheest et al., 2014; Harber et al., 1998).
Figure 2: Cover Story: Dining Out. (Mouly and Kaneko, 2011)
Balanced and adequate nutrition is provided through optimal calories, macro/micronutrients, and fluid intake. The proper determination of nutrition according to age, gender, type of sport, and environmental conditions increases the success rate in general health and sports (Beals and Manore, 2007). There is also evidence that there is an increase of approximately 6-20% in the recovery of physical activity and post-exercise recovery depending on the improvement of nutrition (Casa et al., 2010).
Figure 3: How health care is turning into a consumer product. (Pascual M., 2022).
Vegetables contain many nutrients, such as dietary fiber, potassium, vitamin A, vitamin C, vitamin K, copper, magnesium, vitamin E, vitamin B6, folate, iron, manganese, thiamine, niacin and choline (U.S. Department of Health and Human Services, 2015). Vegetables and fruits are the main and very important sources of vitamins and minerals in the diet of athletes due to the high risk of loss of macro and micro elements excreted by sweat. High importance is attached to the appropriate sodium-phosphorus ratio in endurance sports. Determining the frequency of vegetable and fruit consumption of athletes before and after the marathon, which helps to maintain the correct water-electrolyte balance in the body, to work the heart muscle and skeletal muscles, to transport the energy substance (glucose) and to transmit the nerve impulses in the body, can play a key role on performance (Orzel et al., 2018).
Figure 4: Netflix: The tech giant everyone is watching. (Unknown, 2018)
There are hypotheses that the brain's perception of the presence of nutritional components in the oral cavity may increase perceptions of well-being, and new performance nutrition options are emerging in the light of solid evidence with new developments (Thomas et al., 2016). Adequate and proper nutrition is very important for health, growth and maturation, optimizing sports performance and minimizing injury, regardless of the age of the athlete. There is a very strong evidence that maintaining this eating habit into adulthood may reduce the risk of many lifestyle diseases, provide strength gain, improve performance by increasing tolerance for intense training, or help recovery after exercise together with physical activity (Bass and Inge, 2006).
Figure 5: Food. Unknown (2021).
Contraction of skeletal muscles during physical exercise increases the energy demand for the muscle. ATP production is difficult for working muscle, and metabolic pathways that oxidize carbohydrates and fats may need to be activated simultaneously to meet this need. The intensity, duration and type of exercise determine the mechanisms by which this extra energy is provided (Hargreaves, 2012; Spriet, 2012). Carbohydrate stores in the body are very low compared to the amount that can be used during exercise, and in long-term intense exercises, carbohydrates can be oxidized at a rate of 3-4 g/min by well-trained athletes (Maughan, 2009). In such athletes, proper nutrition is very important in terms of closing the energy deficit. Recovery of muscle and liver glycogen stores after exercise is a rather slow process, and full recovery may not occur until 24-48 hours after the end of exercise (Piehl, 1974). It is thought that the appropriate amount of calories, protein and carbohydrate consumption can be facilitated with the right dietary supplements (Kerksick, Harvey et al., 2008). In addition, training nutrition for strength-strength athletes is sport-specific and plays a key role in supporting strength training, recovery after training, and training adaptations (Lambert and Flynn, 2002; Piehl, 1974). High-quality dietary proteins, maintenance, repair and synthesis of skeletal muscle proteins are very important (Tipton et al., 2007). Whole milk, lean meat and dietary supplements that provide milk-based protein and isolate proteins whey, casein, soy and eggs after resistance exercise is effective in increasing muscle protein synthesis in relation to training to improve body composition and increase muscle strength (Josse et al., 2010; Hartman et al., 2007; Josse et al., 2011). Fat can be considered as a component of a healthy diet, providing energy, forming the essential elements of cell membranes, and facilitating the absorption of fat-soluble vitamins (U.S. Department of Health and Human Services, 2015; Health Canada Eating Well with Canada's Food Guide, 2015).
When the surveys on the strategies of Kenyan and Ethiopian distance runners for carbohydrate consumption are examined, it is seen that the world's best endurance athletes consume especially high-carbohydrate diets (Maughan et al., 2012). Low carbohydrate stores are a factor in fatigue and poor performance in many sports. Nutrition plays a distinctive role in competitive sports. When athletes train more than once a day and their run times are close to each other, rapid recovery of muscle carbohydrate stores is essential (Maughan et al., 2012) Consuming carbohydrate-rich foods and beverages immediately after a workout aids in rapid refueling, as muscle cannot store glycogen effectively in the absence of carbohydrate intake. In many sports lasting longer than an hour, depletion of carbohydrate stores causes fatigue and decreased performance throughout the activity. Conversely, nutritional strategies that provide adequate carbohydrates can reduce or delay the onset of this performance decline. Strategies include carbohydrate intake hours or days before the event to ensure muscle and liver glycogen stores are well stocked with anticipation of the activity's fuel needs. In the absence of muscle damage, the athlete can normalize muscle glycogen stores in as little as 24 hours with carbohydrate-rich diet and exercise reduction. Athletes competing in events that last longer than about 90 minutes can benefit from a 'carb load' a few days before the competition (Maughan et al., 2012)This strategy involves meeting the highest targets for carbohydrate intake (9-12 g/kg/day) for 24-48 hours, while exercise is easily reduced and supercompensate muscle glycogen stores above normal levels (Maughan et al., 2012) As a result, the athlete must have the fuel to exercise longer at their optimal output before encountering performance degradation.
When the strategies for fluid consumption in athletes are examined, the need to drink before, during and after exercise and sometimes the use of beverages containing added carbohydrates and salt is very important. Just as general training and competition strategies should be tailored to the unique needs and preferences of individual athletes, so should their drinking and eating preferences during exercise. Fluids consumed during exercise can play a number of roles. These include providing a means to make the athlete feel more comfortable, to compensate for the lack of body fluid, and to consume other materials (Maughan et al., 2012). It's rarely necessary to drink during exercise that lasts less than about 40 minutes, but some athletes feel better after rinsing their mouth with cold drinks, and that shouldn't do any harm. Meanwhile, during training or competition sessions that last longer than this, there may be opportunities and advantages to drinking during the session. When it is not possible to drink during “heavy sweating” type exercise lasting longer than 30 minutes, it is an alternative to hydrate well just before starting the session. The athlete should practice drinking during the 15 minutes before the exercise and find out how full he is at the beginning but how comfortable he is when the exercise starts (for example, 300-800 ml) (Maughan et al., 2012). Sweating causes loss of water and salt from the body, but although these losses are not significant, water is lost continuously in the breath and through the skin. Small water losses have no effect on performance, but severe dehydration is detrimental to performance. There is no clear evidence at what point performance begins to be affected, and this is almost certainly dependent on the type and duration of exercise and environmental conditions, as well as between individuals.
Figure 6: The quantified self. (Chankova, 2022)
Dehydration resulting from sweat loss or insufficient fluid intake may impair performance during prolonged exercise. Therefore, proper fluid intake before, during, and after exercise is crucial for health and optimal performance. Proper hydration is important for the prevention of metabolic stress and thermoregulation during exercise (Herring et al., 2013). Athletes can lose 0.3 to 2.4 L of sweat per hour, and rates can vary widely with environment, gender, body size, and duration of activity (Thomas et al., 2016). According to Friedman and Elliot, consuming sports drinks during exercise causes endurance performance to be sustained longer. It is recommended that the fluids taken by endurance athletes during training or competition should contain 4-8% carbohydrates and electrolytes (Duvillard et al., 2004; Friedman and Elliot, 2008). Athletes are generally advised to drink only when they are thirsty, but this may not always be reliable. In addition, the rules and possibilities of drinking liquids in many sports may not coincide with the moments of thirst. A more targeted option is to develop a fluid plan tailored to sport, individual, and other nutritional needs. Replacing water and salts lost through sweat is an important part of the healing process. Since sweat and urine losses continue to occur during recovery, the athlete will need to drink approximately 1.2-1.5 liters of fluid for each kilogram of weight loss in training or competition to compensate and fully regain fluid losses (Maughan et al., 2012). Sodium, the main salt lost through sweat, also needs to be replaced. Sodium replacement can be achieved with sodium-containing fluids such as sports drinks and pharmacy oral rehydration solutions. High salt losses may be a contributing factor in some cases of muscle cramps. Sports drinks with higher salt (sodium) levels (e.g., 300-500mg sodium per 500ml of liquid) may help reduce the risk of cramps (Maughan et al., 2012).
Iron plays an important role in the transport of oxygen in the blood (as hemoglobin) and muscle (as myoglobin), and insufficient iron status can clearly impair performance and recovery. There is some evidence that an athlete's iron requirements may be elevated due to increased loss levels due to training load. However, most athletes with iron deficiency or anemia do so because of poor iron intake (Maughan et al., 2012). Iron deficiency, with or without anemia, can impair muscle function and limit working capacity, creating a risky situation for training adaptation and athletic performance (Lukaski, 2004; Wolinsky and Driskell, 2005). Athletes at high risk for such problems are those who restrict their energy intake and diet variety. Because meats, including fish and poultry, are the main sources of well-absorbed iron, vegetarians should plan their meals carefully to find alternative sources of iron. Female athletes are also at risk for increased iron requirements due to menstrual blood losses corresponding to a smaller food intake. An iron-rich diet will help reduce this risk. Athletes at risk for poor iron status should be monitored periodically. Routine use of iron supplements is not recommended. Too much iron is just as harmful as too little iron. Calcium is important for healthy bones, especially in adolescents and female athletes, so it's important to ensure adequate calcium intake. The best sources of calcium are dairy products, including low-fat varieties (Maughan et al., 2012). Calcium is very important for the growth, maintenance, and repair of bone tissue, regulation of muscle contraction, neural transmission, and normal blood coagulation. Low bone mineral density and risk of stress fractures increase with low energy availability, and for female athletes, menstrual dysfunction, low dietary calcium intake may increase the risk (Lukaski, 2004; Nickols-Richardson, 2006; Nattiv et al.; 2007). According to some studies, Vitamin D regulates calcium and phosphorus absorption and metabolism and plays an important role in maintaining bone health (Pojednic and Ceglia, 2014). Vitamin D may have effects on supporting athletic performance by mediating muscle metabolic function (Sinha et al.; 2013). In addition, it may be effective in injury prevention, rehabilitation, improved neuromuscular function, increased type II muscle fiber size, decreased inflammation, and reduced stress fracture risk (Ruohola et al., 2006; Larson-Meyer et al., 2010; Cannell et al.; 2009; Halliday et al., 2011).
The effects that may arise if the energy needs of the athletes cannot be met have been mentioned. In addition, information about which type of food should be used at which stage and the effects of athlete performance if used are given. Based on information, the main differences between sports branches are due to the energy systems used and the contribution of the required nutrients to the total energy, however, the most important nutritional element for all athletes is carbohydrates. It is known that the protein requirement increases in sports branches that require strength/power and in athletes with high muscle mass, but other nutrients (vitamins, minerals, fats) should be consumed adequately. Ensuring adequate hydration is important for all athletes. Fluid loss should be compensated by monitoring the weight lost before and after the athlete's training. Even in the same sports branch, nutrition should be individual for each athlete.
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Figure 1: Unknown (2020). Human metabolism vector banner. [photo]. Retrieved from https://www.istockphoto.com/tr/vekt%C3%B6r/insan-metabolizmas%C4%B1-vekt%C3%B6r-afi%C5%9Fi-gm1290890754-386161046?phrase=energy%20metabolism
Figure 2: Mouly and Kaneko, (2011). Cover Story: Dining Out. The New Yorker. [photo]. Retrieved from https://www.newyorker.com/culture/culture-desk/cover-story-dining-out
Figure 3: Pascual M., (2022).How health care is turning into a consumer product. The Economist. [photo]. Retrieved from https://www.economist.com/business/how-health-care-is-turning-into-a-consumer-product/21807114 Figure 4: Unknown, (2018). Netflix: The tech giant everyone is watching. The Economist. [photo]. Retrieved from https://www.economist.com/weeklyedition/2018-06-30
Figure 5: Food. Unknown (2021). The Economist. [Photos]. Retrieved from https://www.economist.com/technology-quarterly/2021-10-02
Figure 6: Chankova S., (2022). The quantified self. The Economist. [photo]. Retrieved from https://www.economist.com/technology-quarterly/2022-05-07