Sports Medicine: All You Wanted to Know About Sports Nutrition and Energy Production – Part 2

NeuroDocDuck FishWrap, FishWrap Archive


Figure 1. Making good diagnoses.


Figure 2. A Balanced diet is the best way to eat for energy and good health.


In Part 1 of this article, we discussed energy production, storage and expenditure.  Part 2 explores how we eat in order to the fuel energy process. We will look at the major constituents that lead to energy for all of our activities, and how this applies to athletes, both sports athletes and weekend warriors. In fact, all of both articles applies to those who exercise a lot to those who are couch potatoes, and especially those with medical disorders of all kinds.

Fuel Requirements


Fuel for Training:

  • Dietary carbohydrate, a macronutrient that supplies 4 calories/gram, is the preferred energy source for the working muscles.
  • Carbohydrate is the predominant fuel for exercise performed at an intensity of 65% of maximal oxygen consumption (VO2max) or more m- the level at which most athletes train and compete.
    • Therefore, consuming daily carbohydrates is imperative to maintain and replenish muscle and liver glycogen stores between bouts of training and competition.


  • Nutrition recommendations for the public are commonly expressed as a percentage of total energy intake – approximately 45-65%. For athletes, it is best to express recommendations in an absolute quantity or relative to body weight (see Figure 2).

FAT NEEDS: 1.0-1.2 grams/kilogram (g/kg)

Preferred Sources: fatty fish, oil-based dressings, nuts, nut butters, avocado, flaxseed oil, olive oil, canola oil (still in question as to ‘healthy or not’)

PROTEIN NEEDS – 1.2-1.8 g/kg

Preferred Sources: lean meats, fish, turkey, poultry, eggs, low fat dairy products, nuts, nut butters, beans and lentils, soy, whole grain cereals and breads



General Training – 5-7 g/kg

Endurance Athletes – 7-10g/kg

Ultraendurance – >11 g/kg

Preferred Sources: whole grain breads and cereal products, corn, peas, sweet potatoes, rice, pasta, fruits, vegetables


Figure 3. Daily macronutrient recommendation for Athletes.


  • Athletes speak more in the language of food versus grams and percentages, so it is important to educate them about (1) the preferred food sources of carbohydrates, and (2) carbohydrate goals per eating occasion. Generally, two-thirds of an athlete’s plate should be composed that supply nutrient dense, carbohydrate-rich foods (more whole foods than processed foods). Often, lack of cooking skills or lack of time to prepare meals causes many athletes to derive a majority of their dietary carbohydrates from more convenience foods (e.g., chips, crackers, candy bars, macaroni and cheese, pizza, beverages with sugar, etc.). These are often higher in fat and lower in fiber, magnesium, selenium, and other micronutrients and health-benefitting phytochemicals.


Complex Carbohydrates:

  • Balancing the diet with carbohydrate sources that are rich in vitamins, minerals, phytochemicals, and fiber is an important strategy to ensure optimal metabolic processes. A variety of fruits, vegetables, and whole grains would be most advantageous at each of the athlete’s primary daily meals (see Figure 2).

Simple Carbohydrates:

  • Because of an athlete’s typically high-energy expenditure, foods that contain simple sugars (honey, maple syrup, juices, sport drinks) can easily fit into a sound training diet; this way, foods high in processed sugars (e.g., high-fructose corn, syrup) are not displacing more nutrient-dense complex sources.

Carbohydrate Replacement Supplements:

  • Athletes who have difficulty eating enough food to consume adequate overall energy and carbohydrate to meet raining demands sometimes consider incorporating commercially available nutritional supplementation that helps boost overall energy and carbohydrate intake. Taken as a whole, these products (e.g., sports drinks, recovery beverages, bars, and gels) can be more practical and convenient pre-, during, and post-training or competition, but should only be used to supplement a well-balanced diet that contains plenty of whole foods.


  • Fuel for Training:
    • If carbohydrate and overall energy intake are adequate to support training, amino acids should account for less than 5% of total energy expenditure. Unlike carbohydrate and fat, no ‘reservoir’ for protein exists. Protein contributes to tissue repair and acts as a component of metabolic, transport, and hormonal systems. Essentially, amino acids are the building blocks for synthesizing tissue. However, protein does supply4 kcal/g and can become a significant energy source under certain circumstances, such as in a low-carbohydrate condition or during prolonged exercise.


  • In general, athletes’ protein requirements are greater than those of their sedentary counterparts are, and most accurately determined relative to body weight rather than as a percentage of total energy intake. Daily protein requirements range from 1.2-1.7 grams/kilograms), for strength-trained (1.6-1.7 g/kg) and endurance-trained athletes (1.2-1.4 g/kg), with no benefit beyond 2 g/kg of body weight.
Specific Athlete GroupRecommendation in g/kg of Body Weight
Endurance Athletes


Strength Athletes


Vegetarian Athletes


Energy-restricted Athletes


Table 1. Recommendations of carbohydrates for different types of athlete.


  • Athletes are encouraged to obtain protein in their diets from a wide variety of plant and animal sources in order to acquire all the essential amino acids along with essential vitamins, minerals, and antioxidants. (See Figure 2. above). Athletes are advised to choose leaner animal sources to avoid a high intake of saturated fat. Preferably, one-third of an athlete’s plate should provide protein-rich foods. There is no benefit to ‘bolusing’ or eating large quantities of protein per meal – generally, 20-40 grams of protein spread over three meals and a couple of protein-containing snacks will easily meet an athlete’s daily protein needs.

Considerations for Vegetarian and Vegan Athletes:

  • Whether vegetarian diets can adequately meet the nutritional needs of athletes and support athletic performance continues to be questioned. (NOTE: I do not recommend such diets to athletes or patients under my care, although exceptions occur for some diseases where such intake is necessary. However, if someone feels compelled by their own reasons to choose such a regimen, I do try to help them use it optimally. Meats provide more than amino acids. They also contain nutritional components that vegetables do not provide. A balanced diet that includes both meats and vegetables, in proper proportion, is a more rounded way to get all the nutrients, not just amino acids that our bodies require.) Although long-term studies are lacking, some observations can be made now:
  • Well-planned vegetarian diets can provide sufficient energy, and an appropriate range of the micronutrients to support performance and health.
    • Vegetarian athletes can meet protein needs from plant sources, with both plant and animal protein appearing to provide equivalent support for athletic performance. Vegetarian athletes should consume at the higher end of current recommended ranges because of the lower digestibility and essential amino acid profile of plant protein.
    • Female vegetarians are particularly at risk for nonanemic iron deficiency, given the lower bioavailability of iron from plant foods.
    • Health professionals should be aware that disordered eating can be masked or perpetuated by the adoption of a vegetarian diet, because it gives a ‘reason’ to be restrictive and eliminate food groups. Especially, if unwarranted weight loss occurs, the athlete should be assessed for a potential eating disorder.
    • Other nutrients of concern, depending on the degree of vegetarianism, may include zinc, vitamin B12, vitamin D, calcium, and other micronutrients.

Protein Supplements and Timing of Intake:


            Figure 4. Dark-Chocolate ‘Protein Shake’.

  • In general, there is no compelling scientific evidence to suggest that athletes need to supplement their habitual diets with protein powder or amino acid supplements. However, there is benefit to consuming a protein-containing snack or beverage after a muscle-damaging workout.
  • Because commercially available ‘protein shakes’ are convenient, palatable, and portable, many athletes may prefer a drink right after a workout. In these circumstances, a drink that provides supplemental protein may be appropriate and beneficial.
  • However, athletes should be advised of what would be a proper amount of protein in a recovery beverage.



    • Dietary fat plays several important physiologic roles, including vital organ protection, thermal insulation, acting as a vitamin carrier, and hunger suppressor. Like carbohydrate, fatty acids provide an alternate energy source and reserve during low-intensity exercise.
      • Free fatty acids (FFAs), intramuscular triglycerides (IMTGs), and circulating plasma triglycerides can supply 30-80% of the energy for physical activity, depending on the training and nutritional status of the individual, as well as the intensity and duration of exercise.
      • Depletion of muscle glycogen stores, (NOTE: in general, insulin puts glucose into cells as fat, and glycogen removes the fat and turns it into glucose to feed energy needs), may limit an individual’s ability to maintain exercise at higher training intensities. As a result, the fuel will shift to the mobilization and oxidation of FFAs as the primary fuel source.
      • Aerobic training enhances the ability of muscle mitochondria to oxidize fatty acids as fuel. In addition, the enhanced responsiveness of adipocytes to lipolysis allows endurance athletes to exercise at higher absolute submaximal exercise levels before feeling the fatigue that results from glycogen depletion.
        •  According to the Dietary Guidelines for Americans, the recommendation for fat is in the range of 20-35% of total calorie intake. Usually, after carbohydrate and protein needs are determined relative to an athlete’s body weight, it is generally recommended that the remaining calories come from dietary fat – usually about 1-1.2 g/kg of body weight – and should be individualized based on the athlete’s physical activity level, energy expenditure, growth stage, nutritional needs, and food preferences.
        • In general, athletes are encouraged to choose food wisely in order to obtain ‘heart-healthy’ fats – the essential fatty acids (omega-3 fatty acids) and unsaturated fats rather than foods that are high in saturated and trans fatty acids that contribute to the onset of atherosclerosis and heart disease.
        • However, very low fat diets (<15%) may harm both performance and health and are discouraged.

Table 2. Pre-, during, and post workout carbohydrate, protein, and fluid recommendations.


  • Micronutrients play a specific role in facilitating energy transfer and tissue synthesis – two functions quite important to the overall performance and recovery of athletes.
  • Generally, if an athlete meets overall energy needs and incorporates a wide variety of nutrient-dense foods, vitamin and mineral recommendations can be made through the diet.
  • Additionally, athletes tend to eat many highly fortified ‘sport’ foods and drinks. However, athletes competing in ‘lean’ (e.g., distance running, gymnastics, diving) or weight-restricted sports (e.g., wrestling, lightweight crew) are often at risk for low or marginal intakes of the micronutrients because of low overall food intake.


  • Functions:
    • Iron is a component of hemoglobin, myoglobin, cytochromes of the electron transport system (see: Part 1 of this article), and some iron-dependent enzymes. Therefore, it greatly influences oxygen transport and energy metabolism.
    • Effects on Performance:
      • Iron deficiency anemia decreases the capacity of skeletal muscle to consume oxygen and produce ATP (see: Part 1 of this article). Low iron stores are a frequent finding in endurance athletes.
      • Important Interventions:
        • Screening: Endurance athletes and all female athletes should have their serum ferritin, hemoglobin, and hematocrit monitored to treat both iron depletion and iron-deficiency anemia.
        • Education About Iron-Rich Foods:
          • Athletes should be informed about types and sources of dietary iron to prevent or augment depletion or deficiency.
          • Supplementation:
            • Currently, decisions as regards iron supplementation are best made on an individual basis, and not as team policy. The treatment for adults with known iron-deficiency anemia often involves three months or less of 100 mg/day of elemental iron taken on an empty stomach. Additionally, supplementation may be warranted for athletes with low serum ferritin levels. For some, extra vitamin C taken at the same time as the iron increases the bioavailability of the iron.



IRON (mg)

Fortified Ready to Eat Cerals

1 oz


Fortified Instant Cooked Cerals

1 packet

4.9 – 8.1

Soybeans, Mature, Cooked

½ cup


pumpkin and squash seed kernels, roasted

1 oz


lentils, cooked

½ cup


spinach, cooked from fresh

½ cup


beef, cooked

3 oz


kidney beans

½ cup


chickpeas, cooked

½ cup



3 oz


prune juice

¾ cup


refried beans

½ cup



Table 3. Common food sources of iron



  • Function: Calcium deserves attention because of the incidence of amenorrhea in female athletes, the role of calcium in bone density, the role in efficient nerve conduction (in this case, messages from the brain to the muscles), and the often low-to-marginal dietary intake of calcium seen in some athletes. Altogether, these factors place athletes at risk for compromised bone and/or increased risk for injury (If there is a dearth of calcium available, it leaches out of bones for use in the body and brain.) The dietary recommended intake (DRI) for calcium is 1000 mg/day for female athletes age 19 to 50, and 1300 for female athletes 9 to 18 years old.
  • Important Interventions:
    • Screening: Female athletes should be asked about current and past dairy product intake and calcium supplements, as well as menstrual history.
    • Education: Female athletes should be educated about the highly bioavailable dietary sources, in addition to the role than menstrual function and overall diet adequacy has on bone health.
    • Supplementation: For athletes with known compromised bone density (female and male), 1500 mg/day of calcium and 800 mg/day of vitamin D are recommended (vitamin D aids in improving absorption of calcium in bones). Calcium supplementation with calcium carbonate or citrate in doses of 500 mg or less taken between meals is recommended to optimize absorption.









8 OZ.



1.5 OZ.



8 OZ.



1.5 OZ.



1/2 CUP



2 OZ.



1.5 OZ.













non-dairy sources



foodserving sizecalcium (mg)
Fortified Cereals1 oz.236-1043

Tables 4 and 4a. Calcium contents of dairy and non-dairy foods.



  • Dehydration: the most common hindrance to performance, but is also the most preventable.
    • Fluid Loss: as little as 1-2% of total body weight can begin to elevate core temperature during exercise, resulting in a negative impact on performance. Dehydration greater than 3% of body weight further disturbs physiologic function and can increase risk for exertional heat illness.
    • Involuntary Dehydration: Humans do not maintain fluid balance during prolonged periods of physiologic or thermal stress when fluid is consumed as desired. Thirst is not an adequate indicator of fluid needs during exercise.
    • Acute and Chronic Dehydration: Acute dehydration can occur in a matter of 2-3 hours. This is most commonly seen in endurance athletes such as marathon runners and triathletes. However, chronic dehydration is less visible and potentially more dangerous, usually resulting from successive days of inadequate fluid replacement. This is often seen during early preseason training in football and soccer. Fevers can cause dehydration, and it is why individuals are advised to drink a lot of fluids when their temperature is elevated (prolonged dehydration can cause fainting, vertigo, and kidney damage which can usually be ameliorated by fluid intake).
    • Fluid Type:
      • Fluids from all foods and beverages contribute to one’s overall hydration status. Water can be an appropriate choice for some athletes, but others can greatly benefit from rehydration fluids that contain carbohydrate (6-8% concentration) and electrolytes. Carbohydrate-electrolyte replacements (‘sports drinks’) can help prompt better overall fluid intake, as well as maintain blood glucose and delay fatigue during intense activities lasting more than 45-60 minutes, and even longer endurance events lasting several hours (e.g., running marathons, etc.).
      • Practical Means to Maintain and Monitor Hydration Status:
        • The preferred strategy for maintain fluid balance at all times during training is to consume fluids before, during, and after training (see: Table 2).
          • Athletes should obtain a pre- and post-exercise body weight, and consume 24 ounces of fluid for each pound of weight lost.
          • Check for Signs of Dehydration:
            • Infrequent urination, dark yellow urine, headache, and weakness should be clear signs and symptoms of dehydration. The athlete should stop at that point and rehydrate with adequate fluids.


NUTRIENT TIMING: Precompetition or Workout Nutrition

  • Purpose:
    • Pre-exercise meals or snacks are geared to ‘top-off’ muscle glycogen stores prior to activity to prevent onset of hunger during exercise, and to optimize hydration status. Because dehydration and energy depletion are results of a cumulative effect of not recovering properly from training, athletes should be conscious of optimal food and fluid choices every day, not only during the few hours before a training session or competition. So, actually, should we all.
  • Timing:
    • Athletes may choose to eat a larger meal 3-4 hours prior to activity because this typically gives plenty of time for digestion. Some may ‘graze’ throughout the time prior to activity, and some may fear eating at all. Carbohydrates and fluids are critical in the time before exercise (see: Table
    • Physiologic Considerations:

Having an ’empty stomach’ prior to competition may be desirable for athletes in contact and high-intensity sports for the fear of vomiting or discomfort.

Athletes should know that the protein and fat content of a meal slows gastric emptying. Thus, higher carbohydrate foods at meals and snacks on the day of competition with more moderate amounts of fat and protein are warranted.

Practical Considerations:

Liquid meals can replace conventional foods for athletes who may report having trouble with solid foods prior to training or competition.

Athletes should be encouraged to try new or unfamiliar in a practice situation prior to using them on a competition/ gameday.

As athletes come in various sizes, shapes, and tastes in food, personal preference and toleration need to be considered in athletes should consume foods and fluids that are well-liked, well-tolerated, usually eaten, and believed to result in a winning performance.

·                                                                                                                                                                                                                                                                        Recovery Nutrition:

·                                                                                                                                                                                                                                        Recovery from strenuous exercise or competition is optimal when athletes are following a high-carbohydrate diet because glycogen stores are maximized.

·                                                                                                                                                                                                                                   Carbohydrate (1-1.5 g/kg) should be consumed immediately following exercise, with an additional 1 to 1.5 g/kg to be consumed every two hours thereafter (see: Table 2).

For muscle-damaging exercise, the addition of protein to a recovery snack or beverage has been shown to be beneficial to stimulate protein synthesis.

WEIGHT AND BODY COMPOSITION ISSUES:  Sports medicine doctors, trainers, and the like receive questions regarding both weight gain and weight loss. Because ‘fad’ dieting’, and muscle-building supplements ‘fat-burners’, and muscle-building supplements are mainstream, some athletes may have skewed and had unrealistic expectations about the amount and rate of body-fat loss and/or muscle gain that is both healthy, genetically feasible, and that may actually deliver enhanced physical performance.

Athletes who desire to lose weight fall into three categories:

Relatively Lean Group:

Members of this group may desire weight-loss for performance or appearance.

  • If the athlete is female and amenorrheic (suppression of normal menstrual flow for any reason other than pregnancy), she may already be restricting intake to a point beyond which further limitation is physiologically inappropriate. It is important to discuss the athlete why chronically maintaining a lower-than-natural weight is detrimental to both health and performance. Since most collegiate athletes will not play professionally, it is important for them to think about their health, both present and future. It is also imperative, however, for those planning to play professionally to think about their future health, as well. Achieving a state of energy balance and a level of body fat that allows normal menstrual function is warranted.

·                                                                                                                                                                                                            Body-fat and lean body mass levels are largely rules by genetics. An attempt to maintain a lower-than-natural weight can harm both health and performance (e.g., recurrent injury or illness, amenorrhea, diminished strength and endurance – except for the amenorrhea, these can also occur in male athletes who are otherwise in this group). Doctor’s, trainers, and coaches should be aware of pathogenic weight control measures (e.g., overexercise, purging, and use of diuretics or laxatives) that athletes might engage in to achieve a lower body weight or body-fat level.

·                                                                                                                                                                                                Please note: this problem does not involve all women athletes, by any measure, just some.




Figure 5. Jared Lorenzen played for Kentucky, the NY Giants, and finished in the National Indoor Football League (NIFL).

Athletes Who Carry Excess Body Weight:

Members of this group may need to lose weight both for health and performance. If training is already maximal, or further aerobic activity would compromise strength or anaerobic training, a modest (300-500 kcal) daily calorie reduction may be acceptable. However, this strategy should be supervised so that there will be no upset to the balances necessary for good health and athletic performance.

The Rapid Weight Loss Group:

This group includes athletes who have little or no excess boy fat, but wish to lose weight to compete in a weight-restricted sport (e.g., lightweight crew, wrestling, and boxing), etc.

The process of rapid weight loss is usually called ‘cutting’ and is typically accomplished by restricting and food and fluids, and increasing fluid loss, (e.g., sweating, spitting) for three to ten days before competition. Precompetition dieting and dehydration are followed by refeeding and rehydrating after weigh-in. This practice is repeated with each competition of the season.

Consequences: From a performance standpoint, even an acute negative energy balance and slight dehydration (1-2%) can negatively affect physiologic function and body composition. This includes decreased lean mass and diminished muscle and liver glycogen stores.

Guidelines for the Reduction of Excess Body Fat

Medical personnel and trainers should review the following with the athlete who needs to lose body fat.

Basic Bioenergetics:

Discuss the creation of an energy deficit.

Timing: Weight loss is best accomplished in the off-season.

Rate: For lean and normal weight athletes, a loss of 0.5-1.0 pound per week is optimal. For an athlete with excess weight, a loss of up to 2 pounds/week may be attempted.

Realistic Schedule: Based on the above rates of weight loss, a significant loss of weight takes several weeks to months to achieve.

Two Methods for Achieving a Negative Calorie Balance:

Food choices and/or eating behaviors: Based on current intake, consider reducing foods that are not nutrient dense and high in saturated fat and processed sugars. Reduce meals eaten out; establish an eating schedule; increase fiber intake; and decrease use of caloric beverages. Often look to episodes of ‘mindless’ or emotional eating when an athlete may be eating for reasons other than physical hunger.

Exercise: Based on current training, determine whether aerobic activity is safe to increase. Is the athlete already at a maximum level of daily training? Will increased aerobic activity impair strength or sprint training? If not, recommend increased aerobic training.

Guidelines for Lean Tissue Gain:

Progressive resistance training and adequate calories are critical for weight gain. However, genetic predisposition, somatotype (body type), maturity level, and compliance determine progress.

Initially increase caloric intake by 500-700 kcal/day.

Meal and snack frequency usually must increase to five-9 times/day. Continuous availability of proper food allows an athlete to eat whenever hunger occurs or on a predetermined schedule.

Diet composition: If food volume is maximal, the next option is to concentrate calories without adding bulk. Strategies might include adding nut butters, nuts (remember that peanuts are legumes and not true nuts), dried fruit, chocolate milk, 100% fruit juices (not fruit punches!), cheese, and sports drinks. Athletes should still adhere to a high-carbohydrate, low-saturated-fat diet.

High caloric supplements: If an athlete is unable to increase calories to the needed level with traditional foods alone, supplements are an option. High-calorie shakes, meal replacement beverages, smoothies, or bars are useful to increase frequency of eating as adding calories. Exact supplement can be individualized according to the athlete’s personal preferences.

Evaluate NEAT: Sometimes athletes who have trouble gaining weight may have a greater NEAT (Non-exercise activity thermogenesis – basal metabolism). Such as fidgeting, or where hundreds of calories are being burned just during everyday activities can cause higher metabolic activity.

Increase protein intake: A positive nitrogen balance is necessary to achieve hypertrophy (abnormal enlargement of a body part or organ). See: previous section for protein requirements.

**It is important for readers to understand that all of the factors discussed here are applicable to all of us. Failure to manage properly these things is inimical to good health and a well-functioning immune system. Nutrition is a very important part of maintaining health, activity levels, and happiness!

All of our Duck athletes receive the very best in the way of nutritional and training advice and assistance!

Not all athletes are so fortunate, especially those who play weekend sports, and those in high school. Opportunities exist to assist these athletes and their non-athletic peers to better understand and utilize nutritional information that will help them optimize their performance and health.

Emphasizing this is a duty for all of us concerning our youth and ourselves.

Part 3 of this article will discuss vitamins, minerals, various supplemental substances; how they work, and what happens when they are reduced or missing.



Figure 6. Oregon Cheerleaders – GO DUCKS for a Fantastic and Healthy 2013 Campaign!


Print Friendly, PDF & Email

FishDuck Has New Off-Season Schedule and see the OUR BELOVED DUCKS Forum!

FishDuck articles will now be on Monday-Tuesday-Wednesday only during the off-season, and then we will go back to seven days a week during the football season beginning in August.

We will have some occasional guest articles later in the week, but the hottest Oregon football information will be posted in the OBD forum!

The Our Beloved Ducks Forum (OBD) is where we we discuss the article above and many more topics, as it is so much easier in a message board format over there.  At the free OBD forum we will be posting Oregon Sports article links, the daily Press Releases from the Athletic Department and the news coming out every day.

Be a part of the forum and stay caught up!  When you wish to post there, do know that you are protected just as you were on FishDuck. Join us on the free forum right here!

Our 33 rules at the free OBD Forum can be summarized to this: 1) be polite and respectful, 2) keep it clean, and 3) no reference of any kind to politics. Easy-peasy!

OBD Forum members….we got your back.  No Trolls Allowed!