Body Composition Assessment CHAPTER OUTLINE Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight Chapter 4 Body Composition Assessment

Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight 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)

Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight Key Terms Overweight: 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

Typical Body Composition of an Adult Man and Woman 4.1 Typical Body Composition of an Adult Man and Woman Essential fat constitutes about 3% of the total weight in men and 12% in women

Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight Critical Thinking Jessica 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?

Assessing Body Composition Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight Assessing Body Composition Research/medical facility techniques Dual energy X-ray absorptiometry (DEXA) Magnetic resonance imaging (MRI) Computed tomography (CT) Total body electrical conductivity (TOBEC)

Assessing Body Composition Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight Assessing Body Composition More common techniques Hydrostatic weighing Air displacement Skinfold thickness Girth measurements Bioelectrical impedance

DEXA Procedure is simple; takes only 15 minutes to administer Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight DEXA Procedure is simple; takes only 15 minutes to administer Not readily available to most fitness participants 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

Hydrostatic Weighing Underwater weighing Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight 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

Hydrostatic Weighing Drawbacks Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight Hydrostatic Weighing Drawbacks Time consuming Not feasible to test large number of people Requires measurement of residual lung volume (if unknown, can be estimated) Difficult to perform on the aquaphobic

Air Displacement Individual sits inside small chamber Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight Air Displacement Individual 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

Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight Skinfold Thickness Based 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 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

Anatomical Landmarks for Skinfold Measurements 4.3 Chest Abdomen Suprailium Triceps Thigh

Skinfold Thickness Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight Skinfold Thickness

Skinfold Technique: Percent Fat Estimates for Women 4.1

Skinfold Technique: Percent Fat Estimates for Men under 40 4.2

Girth Measurements Requires a standard measuring tape Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight Girth Measurements Requires a standard measuring tape Women: Upper arm, hip, and wrist measurements (cm) Look up constants on Table 4.4 based on measurements and determine body density and percent fat according to predicting equations Men: Waist and wrist measurements (inches) Use Table 4.5 for percent body fat estimate

Girth Measurement: Conversion Constants to Calculate Body Density for Women 4.4

Girth Measurement: Estimated Percent Body Fat for Men 4.5

Bioelectrical Impedance Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight 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 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

Body Composition Classification according to Percent Body Fat 4.10

Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight 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

Disease Risk according to BMI 4.7

Disease and Mortality Risk Based on BMI 4.6 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

Overweight and Obesity Trends in the United States 4.7

Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight Waist Circumference Predicts disease risk according to the way people store fat (waist versus other areas) Disease Risk according to WC 4.8

Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight Waist-to-Hip Ratio Predicts disease risk according to “apple” or “pear” shape Disease Risk according to Waist-to-Hip Ratio 4.9

Body Composition Changes for Adults in the U.S 15.8 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

Recommended Body Weight Determination Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight 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 formula RBW = LBM ÷ (1.0 – DFP)

Recommended Body Weight Determination: Example Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight Recommended Body Weight Determination: Example Sex: female Age: 19 BW: 160 lbs %F: 30% (.30 in decimal form) FW = BW x %F FW =160 x .30 = 48 lbs LBM = BW – FW LBM =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

Essential and Storage Fat Techniques to Assess Body Composition Determining Recommended Body Weight Critical Thinking How 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?

Effects of a 6-Week Aerobics Exercise Program on Body Composition 4.9 Loss of lean body mass can be offset or eliminated by combining a sensible diet with physical exercise

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