bpk 142 @ sfu | lecture two: anthropometry & body composition

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.