© 2010 cengage-wadsworth chapter 4 body composition outline: 1.essential & storage fat...

© 2010 Cengage-Wadsworth

Chapter 4Body Composition

Outline:1.Essential & Storage Fat2.Techniques to Assess Body Composition3.Determining Recommended Body Weight4.Importance of Regular Body Composition Assessment


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Key Terms

• Body 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)


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Key Terms

• Overweight: An excess amount of weight against a given standard such as height or recommended percent body fat

• Obesity: An excessive accumulation of body fat usually at least 30% above recommended body weight


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Height/Weight Tables

• An individual might appear to be overweight according to height/weight tables but not have too much body fat

• Examples are football players, body builders, other athletes with large muscles

• Some people may look skinny or underweight when they actually are overweight because of their high body fat

• Physical inactivity and a constant negative caloric balance both cause a loss in lean body mass


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Essential and Storage Fat

• Total fat in the human body can be classified into two types

• 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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Typical body composition of an adult man & woman

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


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Body Composition

• Storage fat serves 3 basic functions:– As an insulator to retain body heat– As an energy substrate for metabolism– As padding against physical trauma to the body

• Men tend to store fat around the waist and women around the hips and thighs


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Techniques to Assess Body Composition: DEXA

• Research/medical facility technique– Dual energy X-ray absorptiometry (DEXA)

– Uses very low-dose beams of X-ray energy

– Measures total body fat, fat distribution, bone density


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Hydrostatic Weighing

• Underwater 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


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Air Displacement

• Individual sits inside small chamber (Bod Pod)

• 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 from the body volume

• Less cumbersome to administer• Takes only about 5 minutes


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The Bod Pod, used for assessment of body composition


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Skinfold Thickness

• Based on the principle that the amount of fat beneath the skin is proportional to total body fat

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

• Skinfold test is done with pressure calipers

• Several sites are measured and percent fat is estimated from the sum of the three sites using Tables 4.1 (women) and 4.2 or 4.3 (men)

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


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Anatomical landmarks for skinfold measurement


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Skinfold Thickness


1 2 3 4Procedure for body fat assessment using skinfold

thickness technique


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Bioelectrical Impedance

• Simpler 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 fat 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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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

• Example– Body Weight = 172 lbs Height = 67 inches

– BMI = 172 x 705 ÷ (67)2 – BMI = 27


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Determination of Body Mass Index (BMI)


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Mortality risk vs. BMI

• BMI is used almost exclusively to determine health risks and mortality rates associated with excessive body weight

• Data indicates that disease risk starts to increase when BMI exceeds 25

• The risk also increases for individuals who are underweight (below 18.5)


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Overweight & obesity trends in the United States, 1960-2000


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Disease Risk According to Body Mass Index (BMI)

• BMI does not differentiate fat from lean body mass or note where most of the fat is located

• Athletes with large amounts of muscle mass can fall into the moderate or high-risk categories


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Determining Recommended Body Weight

• Some evidence indicates the mortality rate for underweight people is high

• The body fat of a healthy thin person is near the high physical fitness standard

• Underweight people have extremely low body fat, compromising essential fat

• Normal physiological functions can be impaired if people fall below the essential fat standards of 3% for men and 12% for women


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Typical body composition changes for adults in the United States

• Because of the typical reduction in physical activity, each year the average person gains 1-2 lbs of body fat and loses a half a pound of lean tissue


1 2 3 4Effects of a 6-week aerobics exercise program on body

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

© 2010 cengage-wadsworth chapter 4 body composition outline: 1.essential & storage fat...

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