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

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

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

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

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

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

4.3 Anatomical Landmarks for Skinfold Measurements Chest Abdomen Triceps Suprailium Thigh

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

4.1 Skinfold Technique: Percent Fat Estimates for Women

4.2 Skinfold Technique: Percent Fat Estimates for Men under 40

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

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

4.5 Girth Measurement: Estimated Percent Body Fat for Men

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

4.10 Body Composition Classification according to Percent Body Fat

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

4.7 Disease Risk according to BMI

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 4.6 Disease and Mortality Risk Based on BMI

4.7 Overweight and Obesity Trends in the United States

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

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 15.8 Body Composition Changes for Adults in the U.S

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

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

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