Sports Performance and Nutrition - A Comprehensive Guide

Energy Requirements for Athletes

If you are serious about athletics, or know someone who is, you already know that athletes are a slightly different breed of human. They flirt with the extreme limits of human physiology, and feed off the adrenaline it produces. Their success often hinges on the most seemingly nominal criteria: seconds, ounces, and inches. Athletes rarely stay content with their progress for long, as a benchmark reached ultimately gives rise to another. They are in a constant strive to become stronger and faster, using the old adage “practice makes perfect” as a motivator to press forward. But no matter where a person falls on the athletic spectrum of recreational to elite, practice will only ever be half the battle. Poor or inadequate nutrition is often implicated in declining physical performance in athletes.^[1]

Science demonstrates how athletic performance changes based on nutritional intake. Athletes who reach and maintain peak performance are consistently the ones who best provide the requisite energy to fuel activity.^[2] These people are able to efficiently convert stored energy in to the power and endurance necessary for athletic success. In order to achieve this, athletes must be vigilant to not only consume the best types of calories, but also the correct amounts. At its simplest physical level, the human form is basically a massive lump of stored energy. We eat energy, in the form of calories to fuel all of the functions that are necessary to live: respiration, circulation, movement, etc. This caloric demand increases proportionally with the number of calories expended in physical activity. Hence, athletes who tend to be very active, have a higher caloric need than the average person. To fully understand what is going on only requires a simple understanding of mathematics: Calories eaten – calories required = net calories.

When more calories are eaten than are required, net calories are positive, the extra calories are stored for future use as fat, and we gain weight. When fewer calories are eaten than are required, net calories are negative, our energy stores shrink, and we lose weight. Any severe imbalance, surplus or deficit, has metabolic implications that diminish athletic performance.^[3] The key to optimal athletic fuelling thus comes down to balance, where the net calories are effectively zero—that is, in a neutral state, where the number of calories eaten roughly matches the number of calories required. Determination of the ideal caloric intake for individual athletes is very important, but unfortunately, outside the scope of this article. In general, a person is consuming the correct caloric intake if they have sufficient energy to compete in their sport without large fluctuations in weight. So long as a person avoids large magnitude deficits and surpluses in energy level, the metabolism appears to be able to self-regulate.^[4]

Existing in an energy neutral state may be ideal for an athlete at their desired body composition, but what about athletes who want to gain, or more commonly, lose weight? They must do so carefully, so to not impact athletic performance. Severe caloric restriction causes the metabolism to drop in order to preserve energy,^[5] which means that the body focuses on nutrient conservation and hinders energy usage in physical activity. When caloric restriction ends, the body reacts by storing calories, which ultimately results in rebound weight gain.^[5] Hence, severe calorie restriction not only impedes athletic performance, but also yields only temporary weight loss. Conversely, athletes who seek to gain weight by grossly over-consuming calories, no matter how rigorous their training schedule, risk decline in athletic performance by storing excess nutrients as fat rather than desired muscle.^[6] The key to modifying weight and body composition is to do so with no more than a 10-20% increase or decrease from their pre-determined energy neutral intake.^[7]

Dietary Guidelines For Athletes

An athlete’s capacity to perform is determined by his or her ability to mobilize energy substrates stored in the body, and shunting them to power muscle contractions. In terms of efficiency, it is highly favourable for adequate energy in the correct form to be readily available at the onset of physical activity. Failure to provide this requisite energy ultimately yields premature fatigue and poor performance. A day-to-day sports nutrition regime seeks to provide the individual athlete with the ideal fuel to power their sport. In order to grasp why a specific nutritional intake is recommended for athletes, one must first understand how energy is utilized in the body. The three major macromolecules are all potential fuel sources for muscle: carbohydrate, fat, and protein. At any given time, a sugar called glucose is coursing through the bloodstream and concentrating in skeletal muscle. At the onset of physical activity, this freely circulating sugar directly powers the muscle until it is exhausted in a period lasting 60-120 seconds,^[8] depending on the level of fitness of the athlete. From this point forward, the body must manufacture its energy by liberating its stored reserves of carbohydrate, fat, and protein, and burning them to create energy, in the presence of oxygen. The substrate the body uses for energy changes depending on the intensity of exercise^[9] with a heavier reliance on glucose with increasing exercise intensity.^[10] By the time an athlete reaches 85% of their maximal output, more than two-thirds of energy is supplied by glucose, with the remainder provided by the long-term fat stores.^[11]

Within the athletic world an almost unfair emphasis is put on protein for its role in muscle building. In reality, protein is the least important nutritional substrate for energy production, providing an almost negligible 3-5% of total energy during high intensity outputs.^[12] The consensus on daily protein need for athletes is 1.5 grams per kilogram of body weight,^[13] meaning that people who regularly consume a high protein diet that includes protein shakes are likely grossly over-consuming. Extra protein does not feed in to muscle building pathways as commonly believed, but instead is either stored as fat for future use, or excreted by the kidneys with a high metabolic burden.^[13] Either way, extreme protein excess is a hindrance, not a benefit, to athletic performance. An athlete should seek to consume approximately 1.0-1.5 g/kg of protein each day, which is 10-15% of total daily calories.^[13]

The real superstar in sports nutrition is carbohydrate. It is the predominant substrate used for energy production in athletes, and therefore it should be the predominant nutritional component fed to the well-conditioned athlete. The daily carbohydrate requirement for the individual athlete varies depending on the sport, with its demand growing with endurance intensity. Since sports nutrition optimization seeks to closely match energy inputs to energy outputs, an athlete’s carbohydrate intake needs to be carefully planned. Low to medium intensity sports require a daily intake of 5-7 g/kg, whereas high intensity endurance sports require 7-10 g/kg,^[14] making up 55-70% of total daily calories. Ensuring adequate carbohydrate availability prior to competition is the single biggest factor in sustaining peak athletic output. Consider that athletes fed a high fat diet were able to sustain peak performance for 57 minutes, those fed a mixed fat and carbohydrate diet climbed to 114 minutes, and those fed a high carbohydrate diet reigned supreme at 167 minutes.^[15] An athlete ‘hits the wall’ when all available carbohydrate has run out, meaning there is no more energy available to fuel muscle and brain function, making continuation of activity both mentally and physically impossible.

Fatty tissue represents our bodies’ long term energy reserve. Even the leanest athlete has a massive reserve of 50,000-100,000 calories of fat, enough to theoretically sustain a person for nearly 2000 km without refuelling.^[16] On paper, it appears to be the perfect fuel source for activity, but unfortunately, it is metabolised far too slowly to keep up with the high metabolic demands of exercise, and there is no evidence to suggest that a high fat diet will have any positive effect on sports performance.^[16] However, as physical fitness improves, an athlete’s body will adapt to better utilize free fats as an energy substrate.^[17] An intake of 20-25% of total calories from fat is sufficient to fuel optimal performance.

Nutritional Timings and Food Choices for Athletes

Once an athlete has a good grasp of the quantity and proportions of energy necessary to optimally fuel their activity, they must implement a strategy to fulfill these requirements. While there is sufficient evidence to show that eating the correct amount of calories is the most important factor in achieving peak performance ^[18]eating the best types of calories at the correct timings certainly plays a large role in the optimization of performance. The daily eating pattern aims to satisfy the energetic toll of exercise, but requires careful augmentation lead up to, during, and shortly after exercise.

As previously discussed, on a daily basis, and according to their specific level of activity, an athlete should feed him/herself the correct number of total calories to achieve an energy neutral state, in roughly the following proportions: 55-70% carbohydrate, 20-25% fat, and 10-15% protein. First and foremost, athletes should spread these calories out evenly, in small frequent feedings throughout the day. One study showed that people who spread their calories evenly experience dramatic performance improvements over those who consume the exact same number of total calories, only in larger and less frequent meals.^[19] Noted improvements include higher power and endurance, a rise in lean body mass, and a drop in body fat.^[20]

There is still little consensus on what constitutes the ‘ideal’ dietary intake of foodstuffs. Asking ten different experts will most certainly yield ten different opinions. However, since athletics take a very high toll on the body, fuelling with the healthiest possible nutrients should be a major priority. A whole foods anti-inflammatory diet, similar to the ‘Mediterranean Diet,’ has been shown to provide a solid nutritional foundation,^[21] while protecting against short-term injury and long-term development of chronic disease.^[22] Inflammatory muscle soreness and joint pain universally affects athletes,^[23] so feeding the body in a way that reduces the inflammatory response can only be of benefit. Vast literature exists on implementing an anti-inflammatory diet. In general it avoids processed foods, red meat, potatoes and dairy, and promotes brightly coloured fruits and vegetables, lean meats and fish, whole grains, olive and coconut oil, nuts, seeds, legumes, and culinary spices.^[21]

Athletes tend to focus more intently on their nutrition immediately leading up to physical activity, and are less vigilant in their day-to-day eating behaviour. This can prove costly, since the nutritional stores that power activity operates most efficiently when filled between physical activity sessions, not immediately before or during.^[24] Many athletes will participate in a purposeful ‘carbohydrate loading’ program to maximize the availability of glucose to power activity, which has been found to be a performance booster for many people.^[25] Nevertheless, nutritional tweaks in the hours leading up to training or competition do have a bearing on performance. A pre-event meal should be eaten 1.5-2 hours before competition that consists of 200-300 grams of easily digestible carbohydrates, in order to saturate sugar stores. Foods with high fibre content, fat, and protein all delay gastric emptying, and should be avoided until after competition to avoid cramping, acid reflux, nausea, and vomiting during competition. Foods that tend to sit well during athletics include pasta, fruit, vegetable juice, and bread. It should go without saying, but never consume foods on competition day that have not been rigorously tested in training.

During competition is an athlete’s time to reap the benefits of all their hard work. For short duration sports, the pre-event nutritional strategy is sufficient for most athletes to sustain optimal energetic output. However, in exhaustive exercise, additional fuelling of carbohydrate and electrolyte, in the form of gel or sports drinks, may be necessary to sustain athletic output. After exercise, athletes are depleted of sugar, and require replenishment. However, due to poor appetite, most athletes delay adequate post-event recovery by 2.5 hours,^[26] worsening next day soreness. The ideal post-exercise meal contains both carbohydrates and proteins, and serves to refill exhausted sugar stores and improve muscle recovery.^[27] A meal consisting of 1.0 g/kg of carbohydrate and 0.1 g/kg of protein should be sought as soon after exercise as the appetite will tolerate.^[28]

Hydration and Ergogenic Aids

Everybody knows that water is a necessity of life. Water is fundamental to nearly every physiologic process in the body that makes physical activity even possible. It maintains blood volume to allow oxygen and nutrient delivery to the muscle, lubricates our joints and lungs, and keeps us from overheating. Yet, the majority of athletes are not getting enough of it before, during, or after exercise.^[29] It is so vital to physical activity that even a seemingly insignificant drop in water volume can seriously hamper performance. With as little as a 2% reduction in water, our physiologic capacity to exercise is impeded, as cardiovascular output and body temperature regulation systems weaken.^[30] Obviously, the level of decline intensifies with the magnitude of dehydration.

The issue with dehydration in athletics stems from our lack of a long-term water storage system, and a misunderstanding of the thirst sensation. Feeling thirsty is not a sign of pending dehydration, as commonly believed, but rather a sign of actual dehydration. Receptors gather bodily information, such as a drop in blood pressure from a declining blood volume, which is interpreted as dehydration, and triggers the brain to release a ‘thirsty signal.’ Since athletes expend water stores at a much higher rate than at rest, by the time they feel thirsty, they may not be able to fully rehydrate themselves without stopping. Athletes need to practice their water intake such that they never have too much or too little water during competition. Actual water requirements depend largely on the needs of the individual and the sport they are participating in, making it difficult to establish general hydration guidelines. However, all athletes should consume a large fluid volume about 1.5 hours prior to competition to fully hydrate, consume fluids at the same rate as water loss during play, then rehydrate with 500-600 ml of water for every pound lost during exercise.^[31]

The most contentious subject in sports nutrition is surely the use of supplements, or ergogenic aids, to increase performance capacity in athletes. A lot of money is spent by the supplement industry to convince athletes to use their product. The actual level of evidence for supplementation in sport is much poorer than the industry would have us believe, with a lot of the benefit attributed to the fact that athletes under consume calories,^[32] and supplements simply allow them to operate at an energy level closer to ideal. Needless to say, there are much cheaper options to fulfill energy requirements than expensive supplement regimes.