Evidence-based Fundamentals of Sports Nutrition by Chase Overpeck

[This is a guest post by Chase Overpeck. Chase is a senior at the University of North Carolina at Chapel Hill and undergraduate researcher in the Exercise Oncology Research Lab. He holds a USA Weightlifting L-1 and is a certified sports nutritionist through the ISSN. He is currently taking part in the Athletic Lab Coaching Mentorship Program. Chase enjoys competing in weightlifting and coaching baseball in his free time.]

All too often, individuals change their habits to become more fit by beginning a new exercise program, but fail to realize or be informed about the nutritional implications of their lifestyle. Imagine buying a new car that requires premium grade gasoline. Filling the vehicle with lower quality fuel than recommended will increase the chances that your engine becomes damaged. This analogy holds true for any level of athlete; insufficient nutrition can inhibit performance and recovery while elevating injury risk (Ray & Fowler 2004). In this blog, we will discuss the role of macronutrients, nutrient timing, and the development of weight-related goals. Additionally, we aim to simplify the process of calculating specific values such as basal metabolic rate (BMR) and activity adjusted energy expenditure as well as provide rationale when developing a meal plan so that you can easily implement this model for yourself and/or clients.

DISCLAIMER: The contents of this article should only be applied to athletic populations. Members of clinical populations may need considerations outside the scope of this discussion and should consult a professional that understands these differences.

MACRONUTRIENT BASICS

CARBOHYDRATE

Carbohydrates serve as the human body’s primary source of energy and are categorized based on molecular complexity. For example, glucose, often referred to as blood sugar in the human body, is a simple carbohydrate and readily provides energy for physiological processes. Glucose can also be stored as a complex carbohydrate in both skeletal muscle and the liver. The storage form of glucose is called glycogen and allows energy to be used later. This is important as glycogen can be used for the increased metabolic demands created by exercise.

Glycogen depletion is a significant inhibitor of exercise performance and is increased as the intensity and/or duration of exercise increases. Therefore, you may see individuals performing intense or prolonged bouts consuming intrasession carbohydrates. Nutrient timing (discussed later) and adequate carbohydrate consumption are essential for combatting glycogen depletion and enhancing performance.

From Table 1, we can see carbohydrate intake recommendations occur within a wide range for athletes due to the varying demands of activity. If we examine the case of a marathoner versus a weightlifter, we see two differing energy systems being stressed. A marathon takes multiple hours and primarily relies upon aerobic pathways to supply necessary energy. A maximal snatch or clean and jerk is performed in a matter of seconds and places the most demand upon the phosphocreatine system, an anaerobic pathway. While doing multiple snatches and clean and jerks along with other higher intensity, repetitive, short bouts is typical, the amount of glycogen used within a weightlifting session is significantly less than that of a marathon. With this rationale in mind, we can better understand Table 1 (Kreider et al. 2010). Because the endurance athlete will need to replenish more glycogen than the strength athlete, they have an increased demand for carbohydrate. We may recommend, for matched/similar activity levels, that endurance athletes opt for the higher value and strength athletes remain on the lower to average values.

PROTEIN

Protein serves the purpose of growth and repair as amino acids (the molecules that form protein) are building blocks for tissue. Proteins also serve as enzymes which regulate physiological reactions within the body. This macronutrient is particularly relevant for active populations due to the muscle damage incurred through exercise.

Muscle protein synthesis (MPS) describes the process by which amino acids form the proteins contained in skeletal muscle such as actin, myosin, and tropomyosin as well as the energy-specific mitochondrial proteins. This is the underlying factor of exercise-related adaptations. To enhance performance, we want to preserve or increase lean mass (depending on our goals). From this standpoint, we want to see MPS occur at an equal or greater rate than muscle protein breakdown (MPB). Examining Phillips et al. 2005, we see that resistance training and amino acid consumption synergistically increased the favorability of MPS to MPB.

The current Recommended Dietary Allowance for protein consumption indicates individuals should consume 0.8g/kg daily (Institute of Medicine 2005). In active individuals, strong evidence suggests that this value is too low and recommends 1.4-2.0g/kg daily (Jäger et al. 2017). Additionally, MPS (nutrient-driven) is a time sensitive process lasting up to two hours. Having a consistently equal or greater rate of MPS to MPB will lead to the most anabolic environment which favors maintenance or accretion of lean mass. The typical human can utilize no more than 0.55g/kg of protein in one serving (Schoenfeld & Aragon 2018). For an 80kg individual, this would translate to 44g of protein in a meal. Due to this lack of carryover, trying to compensate by overloading one meal relative to others creates a less favorable environment of MPS to MPB over the course of the day. Therefore, it is important to have multiple, distributed, adequately stimulating (20-25g of complete protein, specifically 3g leucine) boluses of protein each day.

FAT

When viewing carbohydrates as our primary energy source and protein as critical for growth and recovery, it may be useful to think of fat as the macronutrient that fills out the remainder of the equation for active populations. These are areas such as hormonal regulation, vitamin absorption, cellular membrane structure, and organ protection.

*Fat is also a provider of energy as well as energy storage; however, for exercise at greater intensities, fat takes a secondary role to carbohydrate. If you are interested in this topic, please read the following which discusses this phenomenon called the crossover concept.

The recommended amount of dietary fat as a percentage of daily caloric intake ranges from 20-35% (Institute of Medicine 2005); however, it is important to understand that this macronutrient is of greater energy density than protein and carbohydrate. Fat yields 9kcal/g while carbohydrate and protein yield 4kcal/g (*due to the thermic effect of feeding, the values are not exactly equivalent for carbohydrate and protein). For an isocaloric diet (total calories are equivalent), we should see individuals who participate in greater endurance activity consume a lower percentage of calories from fat compared to a strength athlete. As a guiding principle, the amount of dietary fat consumed by an athlete should be around 1g/kg. Falling below this threshold could lead to issues related to hormonal maintenance. As we will discuss later, exceeding this value can be beneficial for individuals looking to gain weight.

NUTRIENT TIMING

To best examine nutrient timing and provide as broad a template as possible, we will divide the day into the following segments: pre-training meals, intra-workout nutrition, and post-training meals.

PRE-TRAINING MEALS

The first period of this section refers to meals consumed 3-4hrs before exercise. These meals would be most representative of a mixed diet concerning a balance of complete proteins (ex: poultry, fish, eggs, tofu), complex, low glycemic index carbohydrates (ex: brown rice, pasta, oat bran, most fruit, vegetables, yogurt, milk), and dietary fat. Complete proteins feature all nine essential amino acids and are often consumed in an omnivorous diet. Individuals who do not consume meat may need to use multiple foods to form meals with complete protein sources. Most carbohydrates appropriate at this meal time will be higher in fiber, less processed, and contain less added sugar. This combination of macronutrients allows individuals to maintain a consistent blood glucose level, create a favorable environment for MPS, and consume dietary fat that would otherwise be limited close before or after training.

This second period refers to meals consumed 15-45min prior to exercise. These meals should lack excessive amounts of fat and fiber as this could cause issues related to digestibility that could inhibit performance. As we are looking to raise energy availability which will have a glycogen sparing effect, we want to consume 50-100g of moderate glycemic index carbohydrate (ex: banana, grapes, crackers, whole grain PB&J+milk). It is important that we do not consume excessive high glycemic index carbohydrates (ex: candy, sugary breakfast cereal, Pop-Tarts®) as this could lead to rebound hypoglycemia. This is the phenomenon by which we have a rise in blood glucose accompanied by a subsequent spike in insulin causing the athlete to feel poorly with symptoms of light-headedness and nausea. Finally, a stimulating (20-25g of protein with three grams of leucine) amount of protein will help promote MPS as we are entering a state where MPB will occur.

INTRA-WORKOUT NUTRITION

This period concerns what we consume throughout our training session. For many individuals, the duration of a training session will not result in enough glycogen depletion that an intra-workout carbohydrate is necessary. This would only be seen in individuals playing a lengthy game (ex: soccer) or performing a long, endurance workout. In this case, athletes should be consuming carbohydrates along with essential amino acids (EAAs) to provide a glycogen sparing effect as well as enhance MPS. This can be done with a small snack (ex: protein bar) or adding EAAs to a sports drink (ex: Gatorade® with mixed in EAA supplement). Branched-chain amino acids (BCAAs) are a popularly advertised supplement, but are often only needed in excess to EAAs for long endurance performance when substrate depletion is so large that protein is used for gluconeogenesis. For the typical training session, hydration will likely play a larger role than glycogen depletion. Maintaining proper hydration concerns both water consumption as well as electrolyte balance. During activities, athletes should aim to replace 16oz of fluid per 1lb of bodyweight lost. Liquid sources containing both carbohydrate and electrolytes can be valuable to athletes; however, the amount of carbohydrate should be considered for issues related to gastric emptying and absorption. A 6% carbohydrate solution (30g of carbs/500mL or 30g of carbs/16.9 fl oz) has similar qualities to water for the aforementioned traits while increasing this to 8% results in a less favorable solution. For example, a typical Gatorade® is 16.9 fl oz and contains 32g of sugar, making it a 6.4% carbohydrate solution.

POST-TRAINING MEALS

The first portion of this period concerns meals consumed up to two hours following a training session. Athletes should focus on consuming high glycemic index carbohydrates (ex: white bread, processed potatoes, rice cakes) and easily absorbable (ex: whey) proteins within 30 minutes of training to optimize the anabolic environment within their body. While not always the best practice, this point in the day would likely be the most optimal to consume a candy bar or sugary snack if one desires. These two measures serve to enhance MPS and replenish muscle glycogen stores (Antonio 2008). Delaying nutrient intake post-exercise beyond 30 minutes reduces these beneficial effects and at the point of two hours, we see a nearly catabolic state within the body.

The second portion of this concerns meals after this initial two hour window following a training session. Carbohydrates should still be consumed as replenishing muscle glycogen is a primary focus; although, it does not need to be as rapid. This means moderate to low glycemic index carbohydrates are sufficient. To maintain a favorable balance of MPS to MPB, it is important to consistently consume adequately stimulating (20-25g of complete protein, specifically 3g leucine) boluses of protein. As we increase further into this period (i.e. longer after the training session), we can begin to consume the mixed diet discussed in PRE-TRAINING MEALS and arrive at the beginning of the cycle.

WEIGHT-RELATED GOALS

While many factors contribute to the ability for one to gain or lose weight, the underlying principle revolves around energy intake and expenditure. For an individual to understand how to manipulate their weight, it is important to understand one’s baseline expenditure. Being alive results in the expenditure of energy, even if we feel like we are not doing anything, and this energy expenditure is called Basal Metabolic Rate (BMR). Strong evidence yields the following formulas to determine this for both males and females based upon age and size (Antonio 2008).

• Males: 66.5 + (13.75* weight in kg) + (5.003* height in cm) – (6.775 * age in yrs)
• Females: 655.1 + (9.5663* weight in kg) + (5.003* height in cm) – (4.676 * age in yrs)

BMR is important, but not representative of every day activity. For these reasons, we also calculate the activity adjusted energy expenditure of an individual to better illustrate their energy demands. Table 2 provides coefficients based upon activity status that can be used along with BMR to determine this value. A good method, although not always feasible, would be to have someone consume a diet at their calculated activity adjusted energy expenditure for seven days and see if there are fluctuations of more than +/-0.25 kg. This could confirm or allow you to adjust the value by 150-300 calories depending on the results yielded by their weight.

WEIGHT LOSS

The primary goal for an athlete looking to lose weight is to maintain as much lean mass as possible while lowering fat mass to a determined threshold. To avoid severe performance decrements related to decreased energy intake, individuals should only decrease consumption by 300-500 calories/day. This will result in weight loss of ~0.25-0.5kg/wk. Maintaining lean mass requires that we lose weight at a slower rate and ensure ample protein consumption. Lowering the ratio of carbohydrate to protein from the usual 3.5-4:1 to ~2-3:1 is a simple guideline that lowers our energy intake while maintaining lean mass and sufficient carbohydrate. Suggestions for weight loss would include increased protein intake (ex: 1.2g/kg to 1.4-1.6g/kg) and decreased carbohydrate and fat intake. Fat should stay near ~1g/kg as recommended; although, in strength athletes where fat is of greater consumption, fat can be manipulated to a greater extent than carbohydrate. The opposite holds true for endurance athletes that already consume less fat and many more carbohydrates; in these individuals, fat can likely not be adjusted to the same extent, so carbohydrates must be reduced. Adequate nutrient timing should be considered to enhance MPS and combat muscle glycogen depletion as these issues can be amplified while operating in an energy deficit.

WEIGHT GAIN

The primary goal for an athlete looking to gain weight is to increase lean mass to a determined threshold while gaining the least amount of fat mass possible. To aid the accretion of lean mass, individuals should be consuming an extra 300-400 calories/day. Increased protein consumption is necessary to support the increase in MPS required. This is a somewhat relative process as extra protein is needed to stimulate greater amounts of MPS. The expected range for most individuals would be between 1.6g/kg-2.2g/kg of protein. Fat should stay near the ~1g/kg suggestion with some exception. If the energy surplus is difficult to reach with more carbohydrates (ex: endurance athlete already consuming a very high amount of carbs), increased fat can be useful due to its relative energy density. A more typical scenario is that fat increases slightly and carbohydrates increase to make up most of the necessary energy surplus. Going off the theme of carbohydrate to protein ratio from weight loss, we may see individuals move from a 3-4:1 diet to 4.5-5.5:1 instead.

EXAMPLE CASE STUDY

Suppose we have a 30 year old male that weighs 100kg and is 180cm tall. The subject goes to fitness classes three times per week after work and he enjoys running once per week. His primary goal is to improve body composition.

Determine BMR:

66.5 + (13.75*100kg) + (5.003*180cm) – (6.775*30yrs) = 2139kcal

Account for Activity:

1.55*BMR=1.55*2139kcal = 3315kcal/day

Adjust Intake for Goal (weight loss):

3315kcal – 400kcal = 2915kcal

Calculate Macros:

PRO: 1.6g/kg * 85kg = 136g
CHO: 5g/kg * 85kg = 425g
Fat: 1g/kg * 85kg = 85kg

Do Macros = Calories?

PRO: 136g*4kcal/g = 544kcal
CHO: 510g*4kcal/g = 1700kcal
Fat: 85kg*9kcal/g = 765kcal Total calories = 3,009kcal ***need 94kcal less***

Adjust as needed:

1. Fat is most energy dense and other macros are within range so start there, but do not deviate too much (maintain ~1g/kg). Removing 5g of fat reduces energy intake by 45kcal and keeps at ~1g/kg (0.94g/kg)
2. Protein will aid retention of lean mass in deficit and appears to be within range whereas for the activity status, carbohydrate could go down slightly if needed (>4.8g/kg). Removing 12g of carbohydrate reduces energy intake by 48kcal and keeps at 4.85g/kg

CASE STUDY RESULTS

• PRO: 136g
• CHO: 413g
• Fat: 80g
• Total calories: 2916kcal

NUTRIENT TIMING FOR CASE STUDY

REFERENCES

1. Ray, T. R., & Fowler, R. (2004). Current issues in sports nutrition in athletes. Southern Medical Journal, 97(9), 863+. https://link.gale.com/apps/doc/A123332696/AONE?u=anon~b0186501&sid=googleScholar&xid=08e65825
2. Kreider, R.B., Wilborn, C.D., Taylor, L. et al. ISSN exercise & sport nutrition review: research & recommendations. J Int Soc Sports Nutr 7, 7 (2010). https://doi.org/10.1186/1550-2783-7-7
3. Phillips, S. M., Hartman, J. W., & Wilkinson, S. B. (2005). Dietary protein to support anabolism with resistance exercise in young men. Journal of the American College of Nutrition, 24(2), 134S–139S. https://doi.org/10.1080/07315724.2005.10719454
4. Jäger, R., Kerksick, C.M., Campbell, B.I. et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr 14, 20 (2017). https://doi.org/10.1186/s12970-017-0177-8
5. Schoenfeld, B. J., & Aragon, A. A. (2018). How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. Journal of the International Society of Sports Nutrition, 15, 10. https://doi.org/10.1186/s12970-018-0215-1
6. Institute of Medicine. (2005). Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press. https://doi.org/10.17226/10490.
7. Kerksick, C.M., Arent, S., Schoenfeld, B.J. et al. International society of sports nutrition position stand: nutrient timing. J Int Soc Sports Nutr 14, 33 (2017). https://doi.org/10.1186/s12970-017-0189-4
8. Antonio, J. (2008). Essentials of Sports Nutrition and Supplements. Humana Press. https://doi.org/10.1007/978-1-59745-302-8

Additional information provided by Abbie Smith-Ryan, Ph.D., CSCS*D, FISSN (University of North Carolina-Chapel Hill) and Khalil Lee, PhD, CSCS (Gatorade Sports Science Institute).