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course taught by Professor Dave Ng
what four main tissues compose the human body?
nervous, epithelial, muscle, connective
what are the three major structural components of the human body?
muscle, skeleton, fat
two-component (2C) model
total body mass is divided into two components; fat mass and fat-free mass
fat-free mass
primaily composed of bone, muscle, water, vital organs, and connective tissue
formula for body masss (two-component model)
fat mass + lean body mass
four-component (4C) model
dives the total body mass into four components; fat, protein, minerals, and water
anthropometry
quantitative measurement of body size and proportions
examples of anthropometric measurements
skinfold thickness, circumerfence, bony widths and lenghts, height, bodyweight
why assess body composition?
monitor changes in body composition; distinguish normal states from disesae states. establish optimal ranges for health and perfomance of athletes. tracking goals
eating disorder
a disturbance in eating behavior, has serious effects on a person’s physical or psychological health
essential fat
fat required for normal physiological functioning
what is essential fat used for?
structural components of cell membranes, synthesis of certain hormones, transport of fat-soluble vitamins
storage fat
fat stored in adipose tissue for energy storage
where is storage fat usually deposited?
underneath the skin (subcutaneous), in the abdominal cavity, and around certain organs
sex-specific differences in body-fat percentage
on average, females tend to have a higher body-fat percentage compared to the average male
‘male type’ or ‘apple shape’ fat deposition pattern
fat is stored more in the upper torso and abdomen
‘female type’ or ‘pear shape’ fat deposition pattern
fat is stored more in the thighs, hips, and buttocks
in females, post-menopause, fat is stored more in the ________ area
abdominal
obesity
an abnormal or excessive accumulation of fat that presents a risk to health
a person is considered obese when… (BMI and BF%)
a person’s body-mass index is greater than or equal to 30, or in men BF% is greater than or equal to 20%, 30% for women
obesity epidemic
obesity rates are increasing every year
causes of the obesity epidemic
caloric intake exceeds caloric expenditure (more intake than outake), decreased physical activity, increased consumption of calories, social environment, biology/epigenetics
epigenetics (in terms of increased risk of obesity)
genetic makeup can lower the threshold for the development of obsesity
changes associated with aging (in terms of body composition)
increased fat mass, decreased muscle mass (sarcopenia), decreased bone mass
how to slow down changes associated with aging
regular exercise and proper dietary habits
common techniques for assessing body composition
direct methods: chemical analysis of human cadavers
indirect methods: noninvasive techniques used on living people
height-weight tables
indirect method of measurement. desirable weight is found by comparing weight and height to death rates.
critisicms of height-weight tables
they estimate health risk. does not consider body composition. data does not considet other ethnicities, income, or age. no method for determining frame size
body density and volume measurement
determines body density by measuring how much a medium (water/air) is displaced when a human body is placed into it. density is then used in an equation to estimate body fat percentage.
weight - height indices (BMI)
used as an indicator of obesity. formula is weight/height²
criticisms of BMI
does not consider body composition, fat distribution, amount of visceral fat. (e.g., someone can be jacked with low BF% but still be classified as ‘overweight/obese’ if they have a lot of muscle)
waist circumference
simple, inexpensive, effective way to assess for central obesity.
skinfold measurements
can be used in equations or tables to predict body fat percentagee
the two types of body composition prediction equations
population specific, generalized
population specific equations (e.g., Yuhasz)
developed from small homogenous samples and application is limited to that subsample
generalized equations (e.g., jackson and pollock, durnin and womersly, peterson, wang)
developed from large heterogenous samples, wider application in terms of age and fatness. use with caution on ‘extreme populations’ (e.g., extremely obese individuals or football players)
o-scale system
developed to combat error of skinfold measurements. uses a stanine scale. provides adiposity rating and proportional weight rating
bioelectrical impedance analysis
measures the body’s resistance to the flow of electricity. impedance is greater in adpipose tissue (less water) than in bone and muscle (more water). i.e., more fat means more electrical impedance
some cons of bioelectrical impedance analysis
fluctions in water content from exercise, dehydration, eating and drinking must be standardized in order to obtain optimal results. clients must follow strict pretest guidelines to get a good estimate of their body composition.
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