© 2010 Cengage-Wadsworth 1234 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

© 2010 Cengage-Wadsworth 1234 Typical body composition of an adult man & woman Essential fat constitutes about 3% of the total weight in men and 12% in women

© 2010 Cengage-Wadsworth 1234 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

© 2010 Cengage-Wadsworth 1234 Hydrostatic Weighing

© 2010 Cengage-Wadsworth 1234 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

© 2010 Cengage-Wadsworth 1234 The Bod Pod, used for assessment of body composition

© 2010 Cengage-Wadsworth 1234 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

© 2010 Cengage-Wadsworth 1234 Anatomical landmarks for skinfold measurement

© 2010 Cengage-Wadsworth 1234 Skinfold Thickness

© 2010 Cengage-Wadsworth 1234 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

© 2010 Cengage-Wadsworth 1234 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 lbsHeight = 67 inches – BMI = 172 x 705 ÷ (67) 2 – BMI = 27

© 2010 Cengage-Wadsworth 1234 Determination of Body Mass Index (BMI)

© 2010 Cengage-Wadsworth 1234 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)