© 2010 Cengage-Wadsworth 1234 Key Terms Overweight: An excess amount of weight against a given...

© 2010 Cengage-Wadsworth

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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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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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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


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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)

© 2010 Cengage-Wadsworth 1234 Key Terms Overweight: An excess amount of weight against a given...

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