Chapter 15 - Body Composition and Nutrition for Sport

body composition

• chemical and molecular

• estimation from a measurement

• fat mass vs. fat free mass

general models of body composition (ways to do it)

• chemical

• anatomical

• two - compartment

Ways that body composition is measured

• densitometry, hydrostatic weighing

• DEXA

• air plethysmography

• skinfold

• bioelectric impedeance

densitometry

• measures body density

• hydrostatic (underwater) weighing

• muscle heavier than water, fat lighter than water

• most commonly used method

limitations of hydrostatic weighing

• lung air volume confounding - must only have residual volume in lungs

• conversion of body density to percent fat

• fat-free density variable among people

DEXA

• dual-energy X-ray absorptiometry

• quantification of bone and soft-tissue composition

• precise and reliable byt expensive and technical

air plethysmography (Bod Pod)

• another densitometry technique

• air displacement (instead of water)

• easy for subject, expensive

skinfold

• most widely used field technique

• thickness measure at a minimum of three sites

• reasonably accurate (quadratic equations)

• the better you are the more accurate the measurements

three sites for female skinfold

• triceps

• suprailliac

• thigh

three sites for male skinfold

• chest

• abdomen

• thigh

bioelectric impedance

• electrode on ankle, foot, wrist, and hand

• current passing from proximal to distal sites

• fat-free mass good conductor, fat poor conductor

• reasonably accurate (room for improvemet)

fat-free mass (including muscle)

• important variable for athletes to know

• good forr power, strength, and muscle endurance

• bad for aerobic endurance (more mass to carry. ex: runners)

relative body fat (percent body fat)

• fat

• less fat usually = better performance

• exceptions: sumo wrestler, swimmer, weightlifter

fat

dead weight, but useful energy stores

weight standards

• guide for optimal body size and composition for a given sport

• possibly misleading

  • athletes define optimal performance

  • but do they define the optimal body?

  • not always

inapproprite use of weight standards

• seriosuly abused by coach, players

• misconception that small weight loss good, large weight loss is better

• possible decrease in performance = eating disorders

making weight

• severe weigh loss

• ex: wrestlers, boxing

• weight classes → extreme weight loss

• competing in class too low → injury, poor health

Risks with severe weight loss

• dehyrdation

• chronic fatigue

• Female Athlete Triad

• disordered nutrition

• menstrual dysfunction

• bone mineral loss

dehydration

• fasting, extreme caloric restriction → water loss

• 2% - 4% weight loss as water → impaired peformance

• risk of kidney/cardiovascular dysfunction, death

chronic fatigue

• underweight → fatigue → decrease in performance, injury

• mimics overtraining and chronis fatigue symptoms

• underweight → substrate depletion (especially carbs)

female athlete triad

• eating, menstrual, and bone disorders

• seen with women with lean-physique, low-body-weight, or endurance sports

• ex: skating, dance, gymnastics, running, swimming

disordered nutrition

• weight standards → disordered eating

• anorexia nervosa, bulimia nervosa

• more prevalent with women in lean sports

menstrual dysfunction

• delayed menarche, oligomenorrhea, or amenorrhea

• prevalent in low-body-weight sports

• due to caloric intake < caloric expenditure

bone mineral loss

• serious conequence of athletic amenorrhea

• anorexia → fracture rate 7x higher

appropriate weight standards

• inappropriate standard, risky for athlete health

• body composition, not total body weight

• optimal range of percent body fat

• recognition of sex differences

weight standards are not always appropriate

• technical measurement errors

• “ideal” composition not always best for performance

acheiving optimal weight

• avoid fasting and crash diets

• optimal weight loss: decrease in fat mass, increase in FFM

avoid fasting and crash diets

• cause more water and muscle loss, less fat loss

• ketosis accelerates water loss

optimal weight loss

• decrease in fat mass, increase in FFM

• moderate caloric restriction + exercise

• caloric deficit about 200-500 kcal/day

• loss less than or equal to 0.5 - 1 kg a week (1-2 pounds a week)

• slowing of weight loss when near goal

recommended carbohydrate

• 55% - 60% of daily calories

• cycled through the most

recommended fat

<35% (<10% satured)

recommended protein

10% - 15%

What are carbohydrates and protein intake based on?

• based on gram per kg of body weight

• individual amount for each person

gram to kilogram ratio for protein

1.2-1.7 g / kg

gram to kilogram ratio for carbohydrates

3- 12 g / kg

classification of nutrients

• Recommended Daily Allowance (RDA)

• Daily Recommended Intake

Recommended Daily Allowance (RDA)

• outdated - not bad, just insufficient

• estimated safe, adequate dietary intakes and minimum vitamin and mineral requirements

Daily Recommended Intake (DRI)

• current standards

• intakes grouped by nutrient function, classification

• Four reference values: EAR, RDA, UL, AI

Four reference values for DRI

1. EAR

2. RDA

3. UL (upper limit)

4. AI

5 Classifications of Nutrients

1. carbohydrates

2. fat (lipid)

3. protein

4. vitamin

5. mineral

molecular composition of carbohydrates (CHO)

• monosaccharides, disaccharides, polysaccharides

• monosaccharides: glucose, fructose, galactose

functions of carbohydrates in the body

• energy source (sole source for nervous system)

• regulation of fat and protein metabolism

composition and storage of carbohydrates

• excess CHO stored as glycogen

• glycogen stores determined by dietary CHO intake

determinants of glycogen replacement

• CHO intake

• exercise type (eccentric decrease in glycogen synthesis)

  • more time to refill tank

glycogen maintenance

• 3-12 g CHO / kg body weight per day

• in athletes, hunger often insufficient drive for CHO

• insufficient CHO intake → heavy, tired feeling

glycemic index

foot categorized by glycemic (blood sugar) response

high GI

• GI > 70

• huge insulin spike, “sugar rush”

• ex: sports drinks, jelly beans, baked/fried potatoes, corn flakes, pretzels

Moderate GI

• GI 56 - 70

• smalled spike, lasts longer

• Ex: pastry, pita bread, white rice, bananas, soda, ice cream

Low GI

• GI of less than of equal to 55

• smallest spike, longest fuel

• Ex: spaghetti, legumes, milk, apples, pears, peanuts, M&M’s, yogurt

GI not perfect

• individual GI reponse varies

• some complex CHOs have high GI

• fat + high GI = lower GI

• GI calculations differ depending on the reference food (glucose vs. white bread)

glycemic load (GL)

• how much carbohydrate you need for a specific amount of time

• improved CHO index

• GL = (GI x CHO, g)/100

CHO factors that increase exercise time

• normoglycemia, low-GI pre-exercise snack

• CHO loading (1-3 days prior)

• CHO feedings during exercise

  • stomach dependent

  • ex: sports drink

• best chance of carbs working for you during exercise

CHO factors that decrease exercise time

• hypoglycemia, high GI pre-exercise snack

  • massive spike

• No CHO loading (lower glycogen stores)

• No CHO feedings during exercise

CHO during exercise

• unlike pre-exercise CHO, does not trigger hypoglycemia

• improved muscle permeability to glycose

• insulin-binding sites altered during exercise

CHO intake after exercise essential

• glycogen resynthesis are high < 2 hours after execise

• protein + CHO intake enhances glycogen stores

• stimulate muscle tissue repair

fat

• essential for body function

• fuel substrate (triglycerides → FFAs + glycerol)

• component of cell membranes and nerve fibers

• required by steroid hormones and fat-soluble vitamins

total fat

<35% of total daily kilocalories (0 trans fat) - tf

saturated fat

< 10% total daily kilocalories

cholesterol

< 300 mg/day

FFA

• important fuel during exercise

• delay exhaustion after glycogen depletion

• body cannot metabolize triglycerides (dietary fat)

• must break down triglyercerides into FFAs

High-fat vs high-CHO diets

• high-fat intake → increased circulation of FFAs (good)

• high-fat intake → decreased glycogen storage (bad)

• no conclusive evidence on high-fat diets

functions of protein

• essential for body function

• cell structure, growth, repair, maintenance

• used to produce enzymes, hormones, and antibodies as a buffer

• control plasma volume via oncotic pressure

how many amino acids are there?

20

how many essential amino acids are there?

9

how many nonessential amino acids are there?

11

protein consumption

• 15% of total daily kilocalories (for normal people, more for athletes)

• about 0.8 protein per kg body weight per day

protein requirements for athletes

• higher

• 1.2-1.7 g protein per kg body weight per day

endurance training

protein possible fuel substrate

strength training

protein needed for building muscle

excessive protein leads to

health risks

CHO + protein intake leads to

improved glycogen and muscle protein synthesis

vitamins

• small but essential organization molecules

• fat soluble vs. water soluble

• unless vitamin deficiency exists, supplementation not helpful

small but essential organic molecules

• enable use of other ingested nutrients

• act as catalyst and cofactors in chemical reactions

fat soluble vitamins

stored, possible toxic accumulations

water soluble vitamins

excreted, toxicity difficult to reach

B-complex vitamins

• 12 total

• essential for cellular metabolism and ATP production

• needed for pyruvate → acetyl-CoA, formation of FAD and NADP, erthyropoiesis

Vitamin C

• important for collagen maintenance, antioxidant

• also for adrenal hormone synthesis, iron abosorption

Vitamin E

• stored in muscle and fat

• potent antioxidant

minerals

• inorganic substances needed for cellular function

• macrominerals vs. microminerals (trace elements)

calcium

• bone density, nerve, and muscle function

• concers: osteopenia, osteoporosis

phosphorus

• bound to calcium in bones

• important for metabolism, cell membranes, buffers, bioenergetics

iron

• critical for hemoglobin, myoglobin (O2 transport)

• deficiency → anemia

• excess → toxicity

sodium, potassium, chloride function

• needed for nerve impulses, cardiac rhythm, fluid, and pH balance

• excess intake dangerous

Where are sodium and chloride found?

intestinal fluid

Where is potassium found?

intracellluar fluid

water and electrolyte balance

• 50-60% of total body weight

• medium for transportation, diffusion

• temperature regulation

• blood pressure maintenance

fat free mass is ____ water

73%

how much body-weight loss happens for sweat in athletes?

1-6%

how much body weight loss through sweat can be fatal?

9-12%

how much of body water is intracellular?

2/3

how much body water is extracellular?

1/3

water gain at rest

• 60% from beverages

• 30% from food

• 10% from cellular respiration (not enough to survive off of)

water loss at rest

• evaporation from skin, respiratory tract (30%)

• excretioin from kidneys (60%)

• excretion from large intestine (5%)

• sweat (5%)

dehydration during exercise

• sweat increases due to higher body temperature

• water loss > water gain

factors in body temperature and sweating

• environmental temperature, radiant heat load

• humidity

• air velocity

• body size

• metabolic rate

the bigger the body…

the higher the resting metabolic rate

impairs aerobic performance

• increased temperature → increased sweat loss → decreased performance

• decrease in plasma → decrease in cardiovascular function (stroke volume gets lower)

• decrease in plasma volume → decrease in thermoregulatory function (can’t make more sweat due to not enough plasma)

effect of dehydratin on anaerobic and strength performance

• unclear

• possibly due to time, not doing these exercises for hours

• ex: sprinting, weight lifting

electrolyte loss in sweat

• sweat is similar to (and derived from) plasma

• include mostly sodium and chloride (concentrations vary), minimal potassium

• remaining ions in body must be redistributed

electrolytes loss in urine

• kidneys regulate electrolyte excretion

• decrease in urine production = decrease in electrolyte excretion

• aldosterone→ sodum retention → increase in thirst and drinking