Lecture 15 - Body Composition Flashcards

1
Q

what is body composition

A

body’s chemical and molecular composition

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2
Q

what are the different body composition models

A
  • chemical model (fat vs protein vs CHO vs H2O vs minerals)
  • anatomical model (adipose tissue vs muscle vs organs vs bon vs other)
  • two-compartment model (fat mass vs fat free mass)
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3
Q

can we measure body fat

A

No, can only estimate

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4
Q

why do we measure body comp

A

provides more information
- heigh and weight not enough to know fitness status
- incre body fat leads to decrease performance
- a bit more precise then BMI

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5
Q

what are the different ways we measure body comp

A
  • densitometry/hydrostatic weighing
  • DEXA
  • air plethysmography
  • skinfold
  • bioelectric impedance
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6
Q

what is densitometry

A

densitometry measures body density
- hydrostatic (underwater) weighing
- muscle is heavier than water, fat lighter than water
- gold standard until DEXA developed

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7
Q

limitations of hydrostatic weighing

A
  • lung air volume confounding
  • conversion of body density to percent fat
  • fat free density varies among ppl
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8
Q

Dexa

A

dual-energy X-ray absorptiometry
- quantifies bone and soft tissue composition
- precise and reliable but expensive and technical

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9
Q

air plethysmography (bod pod)

A
  • another densitometry technique
  • air displacement instead of water
  • easy for subject, difficult for operator, expensive
  • can’t have hair
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10
Q

skinfold technique

A
  • most widely used field technique
  • measures thickness at a minimum of three sites
  • uses quadratic equations, reasonably accurate
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11
Q

bioelectric impedence

A
  • electrodes on ankle, foot ,wrist and hand
  • current passes from proximal to distal sites
  • fat free mass good conductor, fat poor conductor
  • reasonably accurate, could be better (affected by menstrual cycle)
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12
Q

fat free mass

A

includes muscle
- important variable for athletes to know
- greater FFM is good for power, strength and muscle endurance but bad for aerobic endurance (more mass to carry)

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13
Q

relative body fat (percent body fat)

A
  • fat: dead weight but useful energy store
  • less fat usually better = better performance
  • exceptions: sumo wrestlers, swimmer (more body fat make them float better and spend less time keeping themselves up), weight lifter
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14
Q

essential fat for men vs women (cant function if its lower)

A

Male is 3% and women is 12%. Breasts are fat

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15
Q

why can’t we have a ideal body size/weight standard for elite athletes

A
  • elite athletes define optimal performance; they are the standard
  • they define performance by not necessarily optimal body (someones body comp might not exactly make sense for the sport but they surprisingly perform very well)
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16
Q

why is it inappropriate to use weight standards in sport

A
  • its seriously abused by coaches and player, spend to much time to have a certain body type instead of performance
  • misconception that small weight loss good, large weight loss better
  • can lead to decrease performance, eating disorders
17
Q

why is making weight bad for sport

A

i.e. wrestling, boxing
- weight classes can force extreme weight loss
- trying to compete in class that is too low leads to injury and poor health

18
Q

severe weight loss by dehydration

A
  • fasting, extreme caloric restriction leads to water loss (water mass loss)
  • 2-4% weight loss as water leads to impaired performance
  • risk of kidney, cardiovascular dysfunction, death
19
Q

how can extreme WL lead to chronic fatigue

A

under weight - >fatigue - > decreased performance and injury
- mimics overtraining and chronic fatigue syndrome
- underweight leads to substrate depletion

20
Q

how can severe WL lead to eating disorders

A
  • weight standards can lead to disordered eating
  • anorexia nervosa, bulimia nervosa
  • more prevalent with women in lean sports
21
Q

how can severe WL lead to menstrual dysfunction

A
  • delated menarch (first period), ogliomenorrhea, or amenorrhea (altered or irregular menstrual cycle)
  • prevalent in low body weight sports
  • due to caloric intake < caloric expenditure we don’t have enough energy to have a period
22
Q

how can WL lead to bone mineral loss

A
  • bone mineral loss is a serious consequence f athletic amenorrhea
  • anorexia leads to a fracture rate 7x normal
23
Q

female athlete triad

A

eating + menstrual + bone mineral disorders
- seen with women in lean-physique, low BW, or endurance sports
- skating dance, gymnastics, running or swimming

24
Q

what must we consider when evaluating appropriate weight standards

A
  • an inapproriate standard risks athletes health
  • body composition, not total body weight
  • optimal range of percent body fat
  • account for sex differences
    weight standards are not always appropriate
  • technique measurement error
  • not all athlete perform best at ideal composition
25
Q

what must we avoid when trying to achieve optimal weight

A

avoid fasting and crash diets
- causes more water and muscle loss, less fat loss
- ketosis accelerates water loss
Optimal WL: decrease in fat mass and increase FFM
- moderate caloric restriction + exercise
- calorix deficit ~200 to 500kcal/day (3500kcall = -1lb of fat)
- lose no more than 0.5 to one kg a week (consider anorexia)
- when near goal, slow weight loss further (slow WL)