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chapter

10Nutritional Factorsin Health and Performance

Chapter Objectives• Identify the protein, carbohydrate, and fat recom-

mendations for athletes.• Discern between dietary recommendations for disease

prevention and recommendations for performance.• Identify & apply appropriate hydration practices for

athletes.• Apply precompetition & posttraining eating strategies

and advise athletes on guidelines for weight gain and weight loss.

• Recognize signs and symptoms of eating disorders.• Understand the importance of having an intervention

and referral system in place for athletes suspected of having an eating disorder.

• Recognize the prevalence and etiologies of obesity.• Assist in the assessment process for obese individuals.

Role of the Nutritionist

• Responsibilities of the nutritionist include the following:– Personalized nutritional counseling: weight loss and

weight gain, strategies to improve performance, menu planning, dietary supplements

– Dietary analysis of food records

– Nutritional education: presentations and handouts

– Referral and treatment of eating disorders

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How to Evaluate the Adequacy of the Diet

• Standard Nutrition Guidelines– Most athletes have two basic dietary goals:

• Eating to maximize performance

• Eating for optimal body composition

Figure 10.1

Standard Nutrition

Guidelineswww.mypyramid.gov

Key Point

• MyPyramid is an excellent starting point from which to evaluate the adequacy of an athlete’s diet. If a diet provides a variety of foods from each group (grains, vegetables, fruits, milk, meat & beans), it is likely adequate for vitamins and minerals. However, if the diet excludes an entire food group, specific nutrients may be lacking.

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Table 10.1

How to Evaluate the Adequacy of the Diet

• Dietary Reference Intakes (DRI)– In 2005, the DRIs replaced the “Recommended

Dietary Allowances.”– The DRI for each nutrient includes the following:

• Estimated average requirement and its standard deviation by age and gender

• Recommended dietary consumption based on the estimated average requirement

• An adequate intake level when a recommended intake cannot be based on an estimated average requirement

• Tolerable upper intake levels above which risk of toxicity increases

Macronutrients

• A macronutrient is a nutrient that is required in significant amounts in the diet.

• Three important classes of macronutrients are protein, carbohydrates, and lipids.

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Macronutrients

• Protein– Structure and Function of Proteins

• More than half of the amino acids can be synthesized by the human body and are commonly called “nonessential” amino acids because they do not need to be consumed in the diet.

• Nine of the amino acids are “essential” because the body cannot manufacture them and therefore they must be obtained through the diet.

• Proteins provide 4 kcal/g.

Table 10.2

Macronutrients • Protein

– Dietary Protein• high-quality (complete) protein: contains all essential

amino acids in adequate quantities to support tissue growth (anabolism) and maintenance. Usually of animal origin (e.g., meat, fish, poultry, eggs, dairy products).

• low-quality (incomplete) protein: deficient in one or more essential amino acids (usually of plant origin, such as grains, beans, vegetables) such that tissue growth and maintenance is not supported. Consuming a variety of incomplete proteins (e.g., vegetarian diet) provide complementary proteins, which can result in a complete protein (e.g., combining beans and rice).

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Macronutrients

• Protein Requirements – General Population

• Assuming that caloric intake is adequate and that 2/3 or more of the protein is from animal sources, the recommended intake for protein for adults is 0.8 g/kg (0.36 g/pound) of body weight for both men and women.

• Expressed as a percent of daily caloric intake, a common protein intake recommendation is 10-15%.

Macronutrients

• Protein Requirements – Athletic Population

• Based on current research, protein requirements for athletes, especially strength/power athletes, are between 1.5 and 2.0 g/kg of body weight, assuming that caloric intake and protein quality are adequate.

• Even aerobic athletes, especially for endurance events lasting greater than 1.5 - 2 hrs, require more protein (1 - 1.5 g/kg) than the general population, because an increasing amount of protein is used as an energy substrate in these long duration events.

• Typically, 15-20% of an athletes total kcal should come from protein, especially strength/power athletes.

Key Point

• Recommendations to increase or decrease protein intake should be made on an indi-vidual basis after the normal diet has been analyzed and caloric intake considered. A mixed diet is the best source of high-quality protein. Strict vegetarians must plan their diet carefully to ensure an adequate intake of all essential amino acids.

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Macronutrients

• Carbohydrates– The primary role of carbohydrate in human

physiology is to serve as an energy source.– Carbohydrates provide 4 kcal/g.– Structure and Sources of Carbohydrates

• Monosaccharides (glucose, fructose, and galactose) are single-sugar molecules.

• Disaccharides (sucrose, lactose, and maltose) are composed of two simple sugar units joined together.

• Polysaccharides, also known as complex carbohydrates, contain up to thousands of glucose units.

Macronutrients

• Carbohydrates – Dietary Carbohydrate

• All types of dietary carbohydrate—sugars as well as starches—are effective in supplying the athlete with glucose and glycogen.

• Consumption of a mix of sugars and starches is desirable.

– Fiber• The DRI for fiber is 38 and 25 g/day for young men

and women, respectively. • This level of fiber may be excessive for some aerobic

endurance athletes.

Macronutrients

• Carbohydrates– Glycemic Index

• The GI classifies a food by how high and for how long it raises blood glucose.

• Foods that are digested quickly and raise blood glucose (and insulin) rapidly have a high GI.

• Foods that take longer to digest and thus slowly increase blood glucose (and therefore stimulate less insulin) have a low GI.

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Table 10.3

Adapted, by permission, from Foster-Powell, Holt, and Brand-Miller, 2002.

Table 10.3Glycemic Index (GI)

of Various Foods

• The table uses white bread (GI = 100) as a standard.

• When variations exist in a food item, the mean is reported.

Macronutrients • Carbohydrates

– Carbohydrate Requirements• The general recommendation is to consume 50 - 55%

of total daily calories as carbohydrate (many athletes need a higher percentage, such as 60-70%, especially during high intensity training).

• Aerobic endurance athletes who train for long durations (90 minutes or more daily) should replenish glycogen levels by consuming maximal levels of carbohydrate, with is approximately 8 to 10 g/kg.

– Calculation Problem: A CSCS prescribes a daily carbohydrate intake of 10 g/kg for an 75 kg triathalon athlete, who is currently training for the ironman competition and has a daily caloric intake of 4500 kcal. What percent of his daily caloric intake is from carbohydrates? A) 57%; B) 60%; C) 67%; D) 70%

Macronutrients

• CHO during exercise– Unlike preexercise CHO, does not trigger

hypoglycemia

– Improved muscle permeability to glucose?

– Insulin-binding sites altered during exercise?

• CHO intake after exercise essential– Glycogen resynthesis high <2 h after exercise

– Protein + CHO intake enhances glycogen stores

– Stimulates muscle tissue repair

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Key Points

• Some aerobic endurance athletes have maximal carbohydrate requirements, up to 10 g/kg per day. During high intensity exercise muscle can use 2-3 g of glucose per min.

• Most athletes do not deplete muscle glycogen on a daily basis, and therefore have lower carbohydrate requirements

(5-6 g/kg per day).

Macronutrients• Lipids

– Structure and Function• Saturated fatty acids, common in animal fats, dairy

products, hydrogenated shortenings, and tropical oils (eg, palm & coconut oil), contain all the hydrogen they can carry. These fats increase LDL “bad” cholesterol, and increase the risk of heart disease.

• Unsaturated fatty acids are missing hydrogen atoms, and carbon atoms are joined together by double bonds. These fats tend to lower LDL cholesterol, decreasing the risk of heart disease.

• Mono-unsaturated fats, common in olive and canola oils, contain one double bond.

• Poly-unsaturated fats, common in sunflower, soy, and safflower oils, contain two or more double bond.

• Fats provide approximately 9 kcal/g.

Table 10.4• Fat, cholesterol, and

Disease– High levels of LDL’s may

contribute to heart disease.

– High levels of HDL’s and decreasing the ratio between total cholesterol and HDL’s protect against heart disease.

– HDLs can be increased by exercise, weight loss, and a diet low in fats (especially saturated fats) and cholesterol.

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Macronutrients

• Lipids– Fat Requirements and Recommendations

• The recommendation for the general public from health organizations such as the American Heart Association is that fat should constitute 30% or less of the total calories consumed.

• It is recommended that 20% of the total calories (or two-thirds of the total fat intake) come from monounsaturated or polyunsaturated sources and 10% from saturated fats (one-third of total fat intake).

• Cholesterol should not exceed 300 mg/day.

Macronutrients

• Lipids– Fat Requirements and Recommendations

• The Sub-Committee on Nutrition of the United Nations recommends an upper limit for fat intake of 35% of total calories for active people.

• The American Heart Association and the Sub-Committee on Nutrition of the United Nations recommend that fat provide at least 15% of the total calories in the diets of adults and at least 20% of total calories in the diets of women of reproductive age.

Key Point

• Fat phobia, or fear of eating fat, can leadto nutrient deficiencies, which harm performance. Athletes who eat very littleor no fat should receive nutritional coun-seling and information.

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Macronutrients

• When Should Athletes Decrease Dietary Fat?– Need to increase carbohydrate intake to support

training type• In this case, to ensure adequate protein provision, fat

is the nutrient of choice to decrease so that that caloric intake can remain similar while carbohydrate is increased.

– Need to reduce total kcal intake to achieve wt loss• Because fat is dense in calories and is highly

palatable, decreasing dietary fat, if the diet has excess fat, can help reduce caloric intake.

– Need to decrease elevated blood cholesterol• Some young athletes are strongly predisposed to heart

disease, although this is uncommon.

Micronutrients

• A micronutrient is a nutrient that is required in small amounts (typically measured in milligram or even smaller quantities) in the diet.

• Two primary types of micronutrients are vitamins and minerals.

• Diets deficient in vitamins and minerals may produce decrements in physical performance.

• Taking a multi vitamin/mineral tablet may ensure that adequate doses of vitamins and minerals are being met.

• There is no scientific data to support the use of mega doses of vitamins and minerals in order to enhance performance

Table 10.5

(continued)

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Table 10.5 (continued)

Table 10.6

• A Key Mineral for Athletes: Calcium - athletes who consume low-calcium diets may be at risk for osteopenia and osteoporosis (deterioration of bone tissue leading to increased bone fragility and risk of fracture).

Table 10.6 (continued)

• A Key Mineral for Athletes (especially women): Iron - a constituent of hemoglobin & myoglobin; plays an important role in oxygen transport & utilization of energy.

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Fluid and Electrolytes• Water

– Water is the largest component of the body, representing from 50-70% of a person’s body weight.

– Total body water is determined largely by body composition; muscle tissue is approximately 75% water, whereas fat tissue is about 20% water.

– Fluid Balance• The average fluid requirement for adults is estimated to

be 2 to 2.7 quarts (1.9-2.6 L) per day.• Athletes sweating profusely for several hours per day

may need to consume an extra 3 to 4 gallons (11-15 L) of fluid to replace losses.

Balance Between Water Gain and Loss

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Dehydration & Exercise Performance

• Thirst– Osmoreceptors (high blood osmolality)

– Baroreceptors (low blood volume)

– Thirst not well calibrated to hydration levels

– 24 to 48 h to completely rehydrate

• Benefits of fluids during exercise– Minimize dehydration and water loss

– Performance and cardiovascular function maintained

Fluid and Electrolytes

• Water – Risks of Dehydration

• Fluid loss equal to as little as 1% of total body weight can be associated with an elevation in core temperature during exercise.

• Fluid loss of 3-5% of body weight results in cardio-vascular strain, impaired ability to dissipate heat, and possible a decrease in performance. At 7% loss, collapse may occur.

• Dehydration will adversely affect endurance training and performance to a greater extent than strength training and performance.

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Key Points

• Consuming adequate fluids before, during, and after training and competition is essential for optimal performance

• The ultimate goal is to start exercise in a hydrated state, avoid dehydration during exercise, and rehydrate before the next training session.

Fluid and Electrolytes

• Water– Monitoring Hydration Status

• Each pound (0.45 kg) lost during practice represents1 pint (0.5 L) of fluid loss.

• Signs of dehydration include the following:– Dark yellow, strong-smelling urine– Decreased frequency of urination– Rapid resting heart rate– Prolonged muscle soreness

• Electrolytes– The major electrolytes lost in sweat are sodium

chloride, and to a lesser extent, potassium.

Fluid and Electrolytes

• Fluid Replacement Guidelines– Before a Training Session

• Encourage athletes to hydrate properly before prolonged exercise in a hot environment.

• Intake should be approximately 16 fluid ounces (0.5 L) of a cool beverage 2 hours before a workout.

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Fluid and Electrolytes

• Fluid Replacement Guidelines– During a Training Session

• Provide cool beverages (about 50-70 °F [10-21 °C]).

• Have fluids readily available, since the thirst mechanism does not function adequately when large volumes of water are lost. Remind athletes to drink.

• Athletes should drink fluid frequently—for example, 4 to 8 fluid ounces (118-237 ml) every 15 minutes.

• For shorter duration exercise (< 1 hr), water is an adequate fluid replacement, but for longer duration exercise (> 1 hr) a carbohydrate drink is warranted (20-30 mEq Na+ & Cl-; 6-8% carbohydrate)

Fluid and Electrolytes

• Fluid Replacement Guidelines– After a Training Session

• Athletes should replenish fluids with at least 1 pint (0.5 L) of fluid for every pound (0.45 kg) of body weight lost.

• Weight should be regained before the next workout.• Water is an ideal fluid replacement, although

flavored beverages may be more effective at promoting drinking.

• The ideal fluid replacement beverage depends on the duration and intensity of exercise, environmental temperature, and the athlete.

Precompetition and Postexercise Nutrition

• Precompetition Food Consumption– Purpose

• The primary purpose is to provide fluid and energy for the athlete during the performance.

– Timing• The most common recommendation is to eat 3 to 4

hours prior to the event to avoid becoming nauseated or uncomfortable during competition.

– Practical Considerations• It is important for athletes to consume food and

beverages that they like, that they tolerate well, that they are used to consuming, and that they believe result in a winning performance.

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Precompetition and Postexercise Nutrition

• Precompetition Food Consumption– Carbohydrate Loading

• Carbohydrate loading is a technique used to enhance muscle glycogen prior to long-term aerobic endurance exercise.

• Postexercise Food Consumption– Data suggest that high-GI foods consumed after exercise

replenish glycogen faster than low-GI foods. – Although emphasis is usually placed on carbohydrate, in

practical terms, consuming a balanced meal ensures the availability of all substrates for adequate recovery, including amino acids.

Weight and Body Composition

• Energy Requirements– Energy is commonly measured in kilocalories

(kcal or calories).• A kilocalorie is the work or energy required to raise

the temperature of 1 kg of water 1° C (or 2.2 pounds of water 1.8° F).

– Factors Influencing Energy Requirements• Resting metabolic rate• Thermic effect of food• Physical activity

Table 10.7

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• Gains in body mass and strength occur when the athlete consumes adequate calories and dietary protein and engages in a progressive resistance training program.

• If all the extra calories consumed are used for muscle growth during resistance training, thenabout 2,500 extra kilocalories are required foreach 1-pound (0.45 kg) increase in lean tissue.

Key Points

Weight and Body Composition

• Weight Loss– If all the expended or dietary-restricted kcal apply to

body fat loss, then a deficit of 3,500 kcal will result in a 1-pound (0.45 kg) fat loss.

– The maximal rate of fat loss appears to be approximately 1% of body mass per week.

– For most people, this is an average of 1.1 to 2.2 pounds (0.5-1.0 kg for 50-100 kg mass individuals) per week, and represents a daily caloric deficit of approximately 500 to 1,000 kcal.

– For athletes who desire to minimize lean tissue loss, small decreases in caloric intake to achieve gradual weight loss are indicated.

Key Point

• The most important goal for weight loss is to achieve a negative calorie balance. Therefore, the types of foods the individual consumes are less important than the portions of those foods. The focus is on calories.

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Eating Disorders: Anorexia Nervosa and Bulimia Nervosa

• Definitions and Criteria– Anorexia nervosa is self-imposed starvation in an

effort to lose weight and achieve thinness.

– Bulimia nervosa is characterized by recurrent consumption of food in amounts significantly greater than would customarily be consumed at one sitting.

Figure 10.2

Reprinted, by permission, from American Psychiatric Association, 1994.

Figure 10.3

Reprinted, by permission, from American Psychiatric Association, 1994.

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Eating Disorders: Anorexia Nervosa and Bulimia Nervosa

• Definitions and Criteria– Warning Signs for Anorexia Nervosa

• Commenting repeatedly about being or feeling fat

• Asking questions such as “Do you think I’m fat?” when weight is below average

• Dramatic weight loss for no medical reason

• Reaching a weight that is below the ideal competitive weight

• Continuing to lose weight even during the off-season

• Preoccupation with food, calories, and weight

Eating Disorders: Anorexia Nervosa and Bulimia Nervosa

• Definitions and Criteria– Warning Signs for Bulimia

• Eating secretively

• Disappearing repeatedly immediately after eating

• Appearing nervous if something prevents the person from being alone after eating

• Losing or gaining extreme amounts of weight

• Smell or remnants of vomit in the rest room or elsewhere

• Disappearance of large amounts of food

Eating Disorders: Anorexia Nervosa and Bulimia Nervosa

• Definitions and Criteria– Warning Signs for Both Disorders

• Complaining frequently of constipation or stomachaches

• Mood swings• Social withdrawal• Relentless, excessive exercise• Excessive concern about weight• Strict dieting followed by binges• Increasing criticism of one’s body• Strong denial that a problem exists even when there is

hard evidence

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Eating Disorders: Anorexia Nervosa and Bulimia Nervosa

• Management and Care– Steps in the Management of Eating Disorders

• Fact finding

• Confronting

• Referring

• Following up

– What Not to Do• The strength and conditioning professional’s job is not

to treat an eating disorder; it is to be aware of warning signs and to refer when a problem is suspected.

Table 10.8

Key Point

• Obesity is not the same condition in each individual. Thorough assessment helps determine which treatment is appropriate and, more important, whether the individual is ready for treatment.