Optimizing You: Everyday Athletes’ Guide to Body Composition and Peak Performance. Part 2

Understanding Energy Systems and Nutrient Timing for Optimal Athletic Performance

Athletes who want to improve their performance must think about how they fuel their bodies as well as the mechanics of their training. The timing and amount of nutrients consumed interact with training to influence energy systems, substrate availability, and, ultimately, training adaptations.

The body’s energy systems are broadly classified into two types: non-oxidative (which includes the phosphagen and glycolytic pathways) and aerobic (which includes the fat and carbohydrate oxidation pathways). The non-oxidative systems provide immediate energy for short bursts of high-intensity activity, with the phosphagen system lasting up to 10 seconds and the glycolytic pathway lasting 10 to 180 seconds. After these times, the body must rely more on oxidative pathways to meet the energy demands of prolonged activities.

This shift between energy systems is not abrupt or exclusive. Several factors influence which pathways are used most frequently, including exercise intensity and duration, frequency and type of training, the individual’s sex and training level, and, most importantly, prior nutrient intake and substrate availability. A complex interplay of these variables is required to achieve a balance that allows for maximum efficiency and performance.
The remarkable plasticity of skeletal muscle is at the heart of this balancing act. It quickly adapts to mechanical loading and nutrient availability, undergoing changes that can have a significant impact on an athlete’s performance. These include increased transport molecule numbers, improved enzymes to regulate metabolic pathways, increased tolerance to metabolic byproducts, and increased muscle fuel stores.

Given the varying requirements of muscle substrates, some of which are abundant, such as body fat, and others, such as carbohydrates, which may require deliberate manipulation, the timing and composition of an athlete’s diet become critical. Carbohydrate supplementation, for example, can be critical for replenishing muscle glycogen stores, which are a critical substrate for long-term performance.
Understanding these energy systems and their interactions with nutrients is essential for developing nutrition strategies that complement training. The goal is not only to ensure that the body has enough fuel for the event but also to develop metabolic flexibility — the body’s ability to switch between fuels efficiently based on the demands placed on it.

In the broader context of athletic training and performance nutrition, these principles emphasise the importance of a well-planned diet that is in sync with the athlete’s training regimen. This ensures optimal substrate availability, supports the metabolic demands of various types of exercise, and contributes to the overall goal of improving athletic performance.

Carbohydrate’s Pivotal Role in Athletic Training and Adaptation

Carbohydrates are important in sports nutrition for a variety of reasons, including their unique properties that affect both performance and adaptation to training. The body’s carbohydrate stores are limited and highly dynamic, making diet and exercise routines easily influenced. This alone calls for a strategic approach to carbohydrate management in an athlete’s diet.

Carbohydrates are essential for fueling the brain and central nervous system, as well as serving as a versatile energy source for muscle work of varying intensities. This is because carbohydrates are utilised in both anaerobic and aerobic energy pathways. Carbohydrates are more efficient than fats for high-intensity activities that rely on oxidative phosphorylation, providing a higher yield of adenosine triphosphate (ATP) for the oxygen delivered to the mitochondria and thus improving overall exercise efficiency.

Furthermore, maintaining high carbohydrate availability has been shown to improve performance during prolonged, high-intensity exercises. Depletion of carbohydrate stores, on the other hand, is associated with fatigue, manifesting as decreased work rates, impaired skill and concentration, and an increased perception of effort. This emphasises the significance of carbohydrate loading before, during, and after events to ensure optimal availability and performance.

Glycogen, the carbohydrate stored in muscles, not only serves as a fuel but also plays an important role in regulating muscle adaptation to training. Low glycogen levels can amplify exercise-induced transcriptional and post-translational responses, enhancing cellular outcomes such as increased mitochondrial content and fatty acid oxidation rates. The “train low” strategy, which involves exercising with less exogenous carbohydrate availability, is a developing practice in sports nutrition, but it requires careful periodization to avoid compromising training intensity and quality.

The athlete’s training or competition schedule should be aligned with personalised carbohydrate intake recommendations, balancing the need for high-quality exercise performance and the enhancement of the training stimulus. However, due to a lack of precise information on substrate requirements during training, sports nutrition must frequently rely on educated guesses using technology such as activity trackers, power metres, and GPS.

General carbohydrate intake guidelines can be prescribed based on the athlete’s body size and the specifics of the session, adjusting intake timing throughout the day and around training sessions to modulate carbohydrate availability. Improving carbohydrate availability is essential for high-quality training sessions within a periodized programme, as well as perfecting competition eating strategies. Furthermore, there is merit in performing certain sessions with low carbohydrate availability to enhance the training stimulus or adaptation. Fasting training sessions or back-to-back workouts without refuelling are examples of how to put this strategy into action.

To summarise, carbohydrate intake must be balanced not only in terms of quantity but also in terms of timing about the athlete’s training demands. While the theory behind exercising with low carbohydrate availability is sound, translating this into improved performance outcomes remains a nuanced and complex process that necessitates a more sophisticated integration into the athlete’s overall training programme.

The Synergy of Protein and Exercise in Athletic Adaptation

Dietary protein interacts with exercise in ways that go beyond simple nutrition; it acts as both a catalyst and a building block in the development and repair of muscle and other tissues like tendons and bones. This complex dance of nutrient intake and physical activity results in structural and metabolic adaptations required for athletic progression.

The body’s response to the increase in amino acid levels — particularly leucine — after protein consumption is at the heart of these adaptations. This increase activates the body’s protein synthesis machinery, allowing muscle protein synthesis (MPS) in response to exercise. According to research, MPS worsens for at least 24 hours after a single bout of resistance training, with a heightened sensitivity to dietary protein during this time. This suggests that consuming protein after exercise and throughout the day has a cumulative benefit for muscle tissue.

Protein consumption benefits more than just resistance training. Aerobic, sprint, and concurrent exercise types all stimulate MPS, though the specific proteins synthesised may vary. Modern recommendations emphasise the importance of protein timing for all athletes, regardless of whether muscle hypertrophy is the goal. This suggests that daily protein intakes should be higher than the Recommended Dietary Allowance (RDA) to optimise metabolic adaptations to training.

Nitrogen balance studies have traditionally served as the foundation for determining the minimal protein requirements to prevent deficiency in inactive individuals. This approach, however, is insufficient for athletes, whose primary goal is to foster training adaptation and performance enhancement rather than simply maintain nitrogen balance. As a result, the modern approach to determining protein requirements for athletes goes beyond the Dietary Reference Intakes (DRIs). It focuses on providing enough protein at the right times to support rapid tissue turnover and enhance the metabolic adaptations induced by training.

As research advances, more refined recommendations are expected to navigate not only total daily protein amounts but also optimal timing, protein quality, and specific guidelines for protein supplements from various sources. This advancement in understanding highlights the nuanced and critical role of protein in sports nutrition and the pursuit of athletic excellence.

Optimizing Protein Intake for Athletes: A Dynamic Approach

Dietary protein and athletic performance have a dynamic relationship that is influenced by a variety of factors such as training intensity and type, the athlete’s energy status, and overall goals. According to current research, athletes need 1.2 to 2.0 grammes of protein per kilogramme of body weight per day (g/kg/d) to support the body’s numerous functions, which range from metabolic adaptations and muscle repair to protein turnover.

Key Points for Athletic Protein Consumption:

1. Quantity: Athletes may need to increase protein intake during periods of intense training or when calorie intake is reduced.
2. Distribution: Protein should be consumed in moderate amounts throughout the day, especially after strenuous workouts, to promote continuous muscle repair and synthesis.
3. Personalization: Protein recommendations should be tailored to the individual’s specific training and competition needs within their periodized programme, taking into account their athletic goals, nutrient requirements, energy balance, and food preferences.
4. Adaptability: Protein requirements can vary depending on an athlete’s level of experience (experienced athletes may require less), the nature of the training (higher frequency, intensity, or new stimuli may increase needs), and carbohydrate and overall energy availability.
5. Energy Availability: It is critical to consume enough energy, particularly carbohydrates, to ensure that amino acids are used for protein synthesis rather than being burned as fuel.
6. Special Circumstances: In special circumstances, such as calorie restriction or injury-induced inactivity, protein intakes may need to be higher (up to 2.0 g/kg/day or more) to prevent lean body mass loss.

It’s also worth noting that the type of protein consumed is important; high-quality proteins with all essential amino acids can be especially beneficial for stimulating muscle protein synthesis. Furthermore, the timing of protein consumption about training is critical; there is an ‘anabolic window’ post-exercise when the muscle is especially receptive to protein.
Finally, while these guidelines provide a structured approach to protein consumption, they should not be overly restrictive. Athletes and their nutritionists must be aware of their bodies reactions and be ready to modify dietary plans as needed. This adaptable, informed approach ensures that protein intake is in sync with the ever-changing demands of training cycles and individual needs, promoting peak performance and adaptation.

Strategic Protein Timing for Enhanced Metabolic Adaptation

Protein timing is an important concept in sports nutrition, especially when it comes to optimizing muscle protein synthesis (MPS) and overall recovery after exercise. The timing, amount, and quality of protein consumed can all have a significant impact on the body’s anabolic response to resistance training or any strenuous exercise regime.

Understanding Protein Timing:

1. Early Recovery Phase: Consuming a high biological value protein in the immediate post-exercise window (0–2 hours after exercise) can significantly improve MPS. This entails consuming approximately 0.25–0.3 grams of protein per kilogram of body weight, which equates to approximately 15–25 grams of protein for most athletes.
2. Continued Intake: In addition to the immediate post-exercise phase, continued protein intake throughout the day contributes to long-term MPS. Regular protein feedings every 3–5 hours at the recommended dosage can help support this ongoing process and may result in chronic muscle protein accretion and functional improvements.
3. Higher Dose Effectiveness: Consuming more than 40 grams of dietary protein in a single sitting has not been shown to increase MPS beyond what is achieved with 15–25 grams. As a result, very high doses may be unnecessary for most athletes, unless they have very large body sizes or are on calorie restriction and weight loss.
4. Gains in Muscle Mass and Strength: Although immediate post-exercise protein consumption has been linked to gains in muscle mass and strength, the exact magnitude of these gains over time, as influenced solely by protein timing, is less certain. Longitudinal studies, on the other hand, appear to support the benefit of immediate protein supplementation after exercise for maximizing strength and hypertrophy gains.
5. Current Policies: Newer recommendations emphasize not only the total amount of protein consumed daily but also the importance of consuming it at strategic times — specifically, post-exercise and at regular intervals throughout the day — to maximize muscle adaptation to training.

Protein intake must be precisely optimized for individual athletes based on factors such as body size, exercise intensity, total daily energy expenditure, and specific training goals. Protein intake is meticulously timed and integrated with overall dietary patterns in personalized nutrition strategies, which can provide athletes with the competitive edge needed for muscle recovery, adaptation, and performance improvement.

High-Quality Protein Sources for Athletes

The choice of protein sources can have significant implications for athletes in terms of muscle protein synthesis (MPS), muscle recovery, and adaptation to training. Here’s a summary of the optimal protein sources based on current evidence:

1. Milk-Based Proteins:

• When consumed post-resistance exercise, milk-based proteins such as whey and casein have been shown to support increases in muscle strength and induce favorable body composition changes.
• Dairy proteins have a high bioavailability and a rich profile of essential amino acids, particularly leucine, which is known for its role in stimulating MPS.

2. Whole Foods:

• Types: In addition to milk, whole foods such as lean meats and eggs are high in protein. They not only provide a complete amino acid profile, but they also provide other nutrients necessary for overall health and recovery.
• MPS Response: Research indicates that whole milk, lean meats, and other foods can help with MPS and overall protein accretion in the body.

3. Plant-based Options:

• Plant-based proteins, while not as extensively studied as animal-based proteins, can also support MPS. Concentrated vegetable proteins, such as soy, are gaining popularity, particularly among athletes who follow vegetarian or vegan diets.
• Considerations: Due to differences in essential amino acid content and digestibility, plant-based proteins may need to be consumed in greater quantities to match the amino acid profile and MPS effects provided by animal-based proteins.

4. Dietary Supplements:

• Convenience: High-quality dietary supplements can be a practical solution for athletes who need convenience or have specific nutritional goals. Isolated protein powders such as whey isolate, casein, soy, and egg protein powders are examples of this.
• Quality Assurance: To avoid contaminants and banned substances, choose supplements that have been third-party tested for quality and purity.

5. Nutrient Timing and Quality:

• Timing: To maximize MPS, protein intake should be consumed as soon as possible after exercise.
• Protein quality, in terms of amino acid profile and digestibility, is critical for optimizing its effectiveness.

6. Personalized Recommendations:

• Before recommending protein supplements, it is critical to assess an athlete’s diet as a whole and consider their specific nutritional goals, energy needs, training and competition schedule, and dietary preferences.
• While supplements can help meet protein requirements, the primary focus should be on eating a well-balanced diet rich in high-quality whole foods to ensure a variety of nutrients that support overall health and performance.

7. Research and Future Directions:

• Ongoing Research: More research is needed to investigate the impact of other high-quality protein sources and mixed meals on MPS and overall training adaptation.

Conclusion: High-quality proteins, especially those high in essential amino acids and leucine, are essential for athletic performance. Milk-based proteins are currently the most studied, but a varied diet with multiple protein sources can be beneficial. When considering supplements, consider the quality as well as the context of the athlete’s overall diet and goals.

The Role of Fat in an Athlete’s Diet

Fat is an essential macronutrient in the diet of an athlete for several reasons:

1. Energy: Fat is a dense source of energy, containing 9 calories per gram, which is more than double the amount of energy found in carbohydrates or proteins. This is especially important for endurance athletes who may require a large amount of energy for extended periods.
2. Cell Structure: Fats are essential for the structure of cell membranes, which is necessary for cell function and tissue health.
3. Vitamin Absorption: Fat-soluble vitamins (A, D, E, and K) require fat to be present in the gut for absorption.
4. Essential Fatty Acids: Certain fatty acids, such as omega-3 and omega-6, are referred to as ‘essential’ because the body cannot produce them; they must be obtained through diet.

Public Health Guidelines on Fat Intake:

• The Dietary Guidelines for Americans recommend that saturated fats account for no more than 10% of daily energy intake and emphasize the importance of including essential fatty acids.

Fat as a Fuel Source:

• Endurance training improves the muscle’s ability to burn fat for fuel, which is advantageous because fat stores are more abundant than carbohydrate stores.

High-Fat, Low-Carbohydrate Diets:

• The benefits of high-fat diets for athletes are still being debated. According to some studies, while fat oxidation rates can be increased, this does not always translate to improved performance, particularly at higher intensities.
• Diets high in fat may also impair the ability to metabolize carbohydrates, which are a more efficient fuel source during high-intensity exercise.

Restricting Fat Intake:

• Excessive fat restriction can result in nutrient deficiencies and impair overall health and performance.
• Chronic low-fat diets (less than 20% of total energy intake) are not recommended for athletes because they may limit essential nutrient intake and lead to a lack of dietary variety.

Considerations for Athletes:

• Athletes’ fat intake should be tailored to their training demands, energy requirements, and body composition goals.
• While a high-fat or low-fat diet may be beneficial in the short term in certain circumstances, these should be carefully managed and not jeopardize overall nutritional balance.
• Most athletes benefit from a well-balanced diet that includes an appropriate amount of fat without going too far in either direction.

In conclusion, fat is essential in an athlete’s diet, not only as a source of energy but also for health maintenance. Dietary strategies involving fat should be tailored to the athlete’s specific sport, training, and competition demands, and overall nutritional needs. For most athletes, the current consensus favors a balanced approach that avoids the extremes of high-fat or low-fat diets in order to optimize performance and health.

Alcohol and Athletic Performance

Alcohol consumption can have several detrimental effects on athletes and their performance. Here are the key points regarding alcohol intake and athletic performance:

1. Caloric Load: Alcohol provides 7 calories per gram, which can contribute to excessive caloric intake without nutritional benefits.
2. Impaired Fat Oxidation: Alcohol can suppress the oxidation of lipids (fats), which is an important energy source, especially for endurance athletes.
3. Increased Unplanned Eating: Alcohol may lead to increased and unplanned consumption of food, which can disrupt an athlete’s diet and body composition goals.
4. Negative Acute Effects: Drinking alcohol before exercise can adversely affect metabolism, thermoregulation, and concentration, impairing performance.
5. Longer-Term Effects: Even after signs of intoxication have subsided, alcohol can affect strength and performance for several hours.
6. Recovery: Post-exercise recovery can be compromised by alcohol. It can impair glycogen replenishment, reduce muscle protein synthesis, and slow rehydration due to its diuretic effect.
7. Cold Environments: Alcohol increases peripheral blood flow, leading to a false sense of warmth while increasing the risk of hypothermia.
8. Other Physiological Impacts: Alcohol consumption can lead to acid-base imbalances, disrupt cytokine and prostaglandin pathways, and compromise glucose metabolism and cardiovascular function.
9. Behavioral Issues: Binge drinking is linked with high-risk behaviors, injuries, accidents, and antisocial activities, which can all be detrimental to an athlete’s career and well-being.

Recommendations for Athletes:

• Athletes are advised to adhere to public health guidelines, which generally recommend moderate alcohol consumption for those who choose to drink.
• Team rules regarding alcohol should also be respected, especially in professional settings.
• It is particularly important to avoid alcohol post-exercise to allow for proper recovery and to avoid the negative impacts on muscle protein synthesis and hydration.
• Minimizing or abstaining from alcohol can benefit athletes by avoiding the negative effects on performance, recovery, and overall health.

In conclusion, while alcohol might be a part of social life, athletes should consider the timing and amount of consumption carefully, especially about training and recovery periods. A cautious approach to alcohol aligns with maintaining optimal athletic performance and health.

Read more — Nutrition and Athletic Performance. Medicine & Science in Sports & Exercise 48(3):p 543–568, March 2016. | DOI: 10.1249/MSS.0000000000000852