chapter 4

Chapter 4

Body Composition Assessment

ChapterOutline

Essential andStorage Fat

Techniques for Assessing Body

Composition

Determining Recommended Body Weight

Importance of Regular Body

Comp Assessment

Hoeger & Hoeger. All slides © Wadsworth Publishing.

Key termsBody composition: The fat and nonfat components of the human body; important in assessing recommended body weight

Percent body fat: Proportional amount of fat in the body based on the person’s total weight; includes both essential and storage fat

Lean body mass: Body weight without body fat

Recommended body weight: Body weight at which there seems to be no harm to human health (healthy weight)



Composition



Comp Assessment


Key termsOverweight: Excess body weight against a given standard such as height or recommended percent body fat; less than obese

Obesity: A chronic disease characterized by excessive body fat in relation to lean body mass; usually at least 30% above recommended body weight

Essential fat: Minimal amount of body fat needed for normal physiological functions; constitutes about 3% of total weight in men and 12% in women

Storage fat: Body fat in excess of essential fat; stored in adipose tissue



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Figure 4.1

Essential fat constitutes about 3% of the total weight in men and 12% in women

Typical body composition of an adult man and woman


Critical thinkingJessica is a gymnast whose coach has asked her to decrease her total body fat to 7%. Can Jessica’s performance increase at this lower percent body fat?

How would you respond to this coach?



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Assessing body composition

Research/medical facility techniquesDual energy X-ray absorptiometry (DEXA)

Magnetic resonance imaging (MRI)

Computed tomography (CT)

Total body electrical conductivity (TOBEC)



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Assessing body composition

More common techniquesHydrostatic weighing

Air displacement

Skinfold thickness

Girth measurements

Bioelectrical impedance



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Comp Assessment


DEXA Dual energy X-ray absorptiometry (DEXA)

Frequently used by research and medical facilities

Considered by many as the standard technique for body composition assessment

Uses low-dose beams of X-ray energy

Measures fat mass, fat distribution pattern, and bone density

Procedure is simple; takes only 15 minutes to administer

Not readily available to most fitness participants



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Hydrostatic weighingUnderwater weighing

Most common technique used for decades

A person’s “regular” weight is compared with underwater weight

Fat is more buoyant than lean tissue

Almost all other indirect techniques have been validated against hydrostatic weighing



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Hydrostatic weighing drawbacks

Time consuming

Not feasible to test large number of people

Requires measurement of residual lung volume

Difficult to perform on the aquaphobic



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Comp Assessment


Air displacementIndividual sits inside small chamber

Computerized pressure sensors determine the amount of air displaced by the person

Body volume is calculated by subtracting the air volume with the person inside the chamber from the volume of the empty chamber (air in the lungs is taken into consideration)

Body density and percent body fat are then calculated

Less cumbersome to administer

Takes only about 5 minutes



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Comp Assessment


Skinfold thicknessBased on the principle that approximately half of the body’s fatty tissue is directly beneath skin

Reliable measurements of this tissue give a good indication of percent body fat

Skinfold test is done with pressure calipers

Several sites are measured

All measurements should be taken on the right side of the body



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Figure 4.2

Chest

Abdomen

TricepsSuprailium

Thigh


Skinfold thickness



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Table 4.1


Table 4.2


Girth measurementsRequires a standard measuring tape

Women: Upper arm, hip, and wrist measurements (cm)

Men: Waist and wrist measurements (inches)



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Table 4.4


Table 4.5


Bioelectrical impedanceSimpler to administer, but accuracy is questionable

Sensors are applied to the skin and a weak electrical current is run through the body to estimate body fat, lean body mass, and body water

Based on the principle that fatty tissue is a less-efficient conductor of an electrical current

The easier the conductance, the leaner the individual

Body weight scales with special sensors on the surface may also be used to perform this procedure



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Table 4.9


Figure 4.6

Because of the typical reduction in physical activity, each year the average person gains 1.5 lbs of body fat and loses a half a pound of lean tissue

Body composition changes for adults in the U.S.


Waist-to-hip ratioPredicts disease risk according to “apple” or “pear” shape



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Body mass index (BMI)Incorporates height and weight to estimate critical fat values at which disease risk increases

BMI = Body Weight (lbs) x 705 ÷ (height in inches)2



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Figure 4.5

Overweight and obesity trends starting in 1960 according to body mass index (BMI)


Table 4.8


Figure 4.4

Even though the risk for premature illness and death is greater for those who are overweight, the risk also increases for individuals who are underweight

Disease and mortality risk based on BMI


Recommended body weight determination

Determine pounds of body weight that are fat (FW):multiply body weight (BW) by current percent fat (%F)(FW = BW x %F)

Determine lean body mass (LBM):subtract weight in fat from total body weight(LBM = BW – FW)

Select a desired body fat percentage (DFP) based on health or high fitness standards given in Table 4.9

Compute recommended body weight (RBW) according to the formulaRBW = LBM ÷ (1.0 – DFP)



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Recommended body weight determination: Example

Sex: female

Age: 19

BW: 160 lbs

%F: 30% (.30 in decimal form)

FW = BW x %FFW =160 x .30 = 48 lbs

LBM = BW – FWLBM =160 – 48 = 112 lbs

DFP: 22% (.22 in decimal form)

RBW = LBM ÷ (1.0 – DFP)RBW =112 ÷ (1.0 – .22)RBW =112 ÷ .78 = 143.6 lbs



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Critical thinkingHow do you feel about your current body weight and what influence does society have on the way you perceive yourself in terms of your weight?

Do your body composition results make you feel any different about the way you see your current body weight and image?



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Figure 4.7

Loss of lean body mass can be offset or eliminated by combining a sensible diet with physical exercise


End of Chapter

chapter 4

Documents

body compositiondetermining

total body fat

excessive body fat

excess body weight

recommended percent

womentypical body composition

human body important

lower percent body fat