lecture #2 from elijahs notes

human body comprised of 4 main tissues:

  • nervous tissue

  • muscle tissue

  • epithelial tissue

  • connective tissue

organs are comprised of several tissue types working together

body made up of three structural components

  • muscle

  • skeleton

  • fat

distribution of structural components varies depending on an individuals

  • sex

  • genetics

  • age

  • lifestyle

body mass = fat mass + lean body mass

“two-component model”

fat and fat-free components

“four-component model”

chemical components

anthropometry

quantitative measurement of body size and proportions (body composition)

why assess body composition

  • helps monitor changes in body composition associated with growth, able to compare this with diseased states of growth

  • distinguish optimal ranges for health and performance of athletes

  • track goals for weight loss muscle growth etc.

  • healthy body comp. is optimal for health typeshiiiiiii

“correlation ≠ causation”

eg. obesity itself does not cause diabetes, obesity causes changes in other areas which then cause diabetes

essential fat & storage fat

essential fat | required for normal physiological function

  • structural components

  • synthesis of certain hormones

  • transport of fat-soluble vitamins

storage fat | stored in adipose tissue for energy

  • located under the skin, (subcutatneous fat) abdominal cavity, and arond certain organs

fat storage works differently in males as oppposed to females

  • males on average have less fat than females

  • different patterns of fat storage depending on sex

    • apple shape “male type”

      • upper torso, abdomen

    • pear shape “female type”

      • thighs, hips, buttocks

      • after menopause fat tends to distribute more in the abdominal region

obesitiy epidemic

obesity rates are increasing every year

causes

  • caloric surplus

    • avg us citizen consumes on avg 445 more calories than maintenance

  • decreased physical activity

    • cars, crowding, automation, technological advances

    • entertainment many hours spent watching tv, video games, sitting at computer

  • increaesed consumption of calories

    • high calorie diets (processed foods w/ high sugar and fat)

    • high sugar intake (pop, juice, etc.)

    • consumption of large portion sizes

  • social environment

    • advertisements, pressure to eat

    • infuence of family and friends

  • biology - epigenetics

body composition and aging

changes associated with aging in an prosperous, industrialized society

  • increaseed fat mass

  • decreaed muscle mass (sarcopenia)

  • decreased bone mass

can be slowed down by regular exercise program and proper die

skeletal fragility in elderly women is related to failure to obtain optimal level of bone mass during childhood.

requires good nutrition, good body comp., and regular exercise

common methods for assessing body comp.

  • direct methods

    • chemical analysis of cadavers

  • indirect methods

    • noninvasive methods used on living people

      • (SEE SLIDES FOR METHODS TOO LAZY TO TYPE RN)

body density and volume measurements (d = m/v)

  • density will vary with amount of body fat

  • greater proportion of fat = lower density

  • underwater weighing or volumetry

    • measure amount of water displaced due to body

after body density is determined, equations can be used to determine %body fat

*BASED ON TWO-COMPONENT MODEL

weight - height indices

  • BMI = mass/height^2

  • used as an indicator of obesity

  • mortality rate increases with “overweightness”

  • BMI does not consider

    • body comp.

    • fat distrib.

    • amount of visceral fat

waist circumference

  • waist circumference is an effective way to assess for central obesity

  • waist circumference and/or waist-hip ratio

skinfold measurements

*read pages 4-1 to 4-3 in laboratory manual

  • RATIONALE - a relationship exists between fat located in depots directly beneath the skin and internal body fat and body density

  • assumptions in using skinfold measurements

    1. constant densities in a two-compartment model

    2. proper identification of measurement site and proper measurement technique

    3. constant compressibility of skin fold

    4. fixed adipose tissue patterning

    5. fixed proportion of internal to external fat

  • two types of body comp. prediction equations

    • population specific equations

    • general equations

  • prediction of % fat from skinfold measurements has error of approx. 3-4% even when all done correctly

o-scale system

  • developed to combat error of skinfold measurements

  • requires eight skin-folds, ten girths, four skinfold-corrected girths and two bone breadths

  • provides adiposity rating and proportional weight rating

  • uses stanine scale

bioelectrical impedance analysis (BIA)

  • uses measure of resistance to flow of electricity in body

  • resistance is greater in adipose tissue than in bone and muscle

  • higher the resistance, the fatter the subject

  • water content in individual needs to be standardized to obtain good results

  • pretest guidelines exist for individuals to get good estimates

  • presdiction equation estimates are validated using underwater weighing

  • equations tend to overesitmate fat in lean and underestimate fat in obese

  • must use population-specific equations

  • % error = 3-5% body fat

other procedures

  • DEXA, CT and MRI

    • downsides

      • u need a lot of money bru

    • these became the gold standard

    • good at distinguishing subcutaneous adipose tissue from visceral adipose tissue

      • waist cirumference is a good predictor of abdominal adiposity but cannot distinguish beteen SAT and VAT

CONCLUSION

results of estimation of body comp. should be interpreted with caution

quiz answer

criterion validity