1. 4
Body Composition

2. Body Composition
To determine recommended body weight, we need to assess body composition
Fat mass or percent body fat
Non-fat component or lean body mass
Percent body fat (fat mass)
Proportional amount of fat in the body based on the person’s total weight
Includes both essential fat and storage fat
Lean body mass: body weight without body fat

3. Body Composition (cont’d.)
Recommended body weight (healthy weight)
Body weight at which there seems to be no harm to human health
Body composition
Fat and non-fat components of the body
Used to assess recommended body weight

4. Recommended Body Weight
To determine whether people are truly overweight or falsely at recommended body weight, assess body composition
Obesity is an excess of body fat
Overweight vs. obese
Overweight: an excess amount of weight against a given standard
Obese: excessive accumulation of body fat, usually at least 30% above recommended body weight

5. Essential and Storage Fat
Essential fat is needed for normal physiological functions
3% of total weight in men; 12% in women
Storage fat is fat stored in adipose tissue
Insulator to retain body heat
Energy substrate for metabolism
Padding against physical trauma

6. Typical Body Composition
Figure 4.1. Typical body composition of an adult man and woman.

7. Techniques to Assess Body Composition
Dual energy x-ray absorptiometry (DXA)
Method to assess body composition that uses very low-dose beams of x-ray energy to measure total body fat mass, fat distribution pattern, and bone density
SEE ± 1.8%
Due to costs, DXA is not readily available to most fitness participants

8. Techniques to Assess Body Composition (cont’d.)
Hydrostatic weighing
Underwater technique to assess body composition; considered the most accurate of the body composition assessment techniques.
“Regular” weight vs. underwater weight (fat buoyancy)
SEE ± 2.5%
Some people are aquaphobic

9. Techniques to Assess Body Composition (cont’d.)
Air displacement
Technique to assess body composition by calculating the body volume from the air replaced by an individual sitting inside a small chamber (Bod Pod)
SEE ± 2.2%
Percent body fat is about 5% higher than hydrostatic weighing

10. Techniques to Assess Body Composition (cont’d.)
Skinfold thickness
Technique to assess body composition by measuring a double thickness of skin at specific body sites
Based on the principle that fat under the skin (subcutaneous fat) is proportional to total body fat
SEE ± 3.5 percent

11. Calipers Used to Assess Skinfold Thickness
Various types of calipers used to assess skinfold thickness

12. Procedure for Skinfold Measurements
Figure 4.2. Procedure and anatomical landmarks for skinfold measurements.

13. Techniques to Assess Body Composition (cont’d.)
Girth measurements
Assesses body composition by measuring circumferences at specific body sites
Women: upper arm, hip, and wrist
Men: waist and wrist
Requires little equipment
SEE ± 4%

14. Girth Measurements
Figure 4.3. Procedure for body fat assessment according to girth measurements.

15. Techniques to Assess Body Composition (cont’d.)
Bioelectrical impedance
Assesses body composition by running a weak electrical current through the body
Fat tissue is a less efficient conductor of electrical current than lean tissue
Simple to administer
Accuracy is questionable
Measurements may be off by as much as 10%

16. Techniques to Assess Body Composition (cont’d.)
Body mass index (BMI)
Technique to determine thinness and excessive fatness that incorporates height and weight to estimate critical fat values at which the risk for disease increases
BMI = [Body weight in pounds x 705 ÷ (height in inches)2]

17. Mortality Risk versus BMI
Figure 4.4. Mortality risk versus body mass index (BMI).

18. Disease Risk and BMI
Table 4.7. Disease Risk According to Body Mass Index (BMI)

19. Techniques to Assess Body Composition (cont’d.)
Location of fat is a better predictor of increased risk for disease than total body fat:
Android obesity (“apple” shape) is fat stored in the trunk or abdominal area
Gynoid obesity (“pear” shape) is fat stored around the hips and thighs
Waist-to-Height Ratio (WtHR): keep your waist circumference (WC) half of your height

20. Disease Risk and Waist Circumference
Table 4.8. Disease Risk According to Waist Circumference (WC)

21. Disease Risk by BMI and WC
Table 4.9. Disease Risk According to Body Mass Index (BMI) and Waist Circumference (WC)

22. Waist-to-Height Ratio
Table Health Categories According to Waist-to-Height Ration (WtHR)

23. Determining Recommended Body Weight
After finding your percent body fat, determine your body composition class
Health fitness standard
High physical fitness standard
Mortality rate is generally higher for obese people, and for underweight people

24. Critical Thinking Do you think you have a weight problem?
Do your body composition results make you feel any different about the way you perceive your current body weight and image?

25. Risk Factors: VSC, SBC, and RTP Fat
Figure 4.7. Visceral (VSC) fat is a greater risk factor for heart diseases, stroke, hypertension diabetes, and cancer than subcutaneous (SBC) or retroperitoneal (RTP) fats.

26. Body Weight and Aging
Your recommended body weight is based on your age and gender
Because lean tissue decreases with age, one extra percentage point is allowed for every additional decade of life

27. Importance of Regular Body Composition Assessment
Adults in the US tend to gain 1 to 2 pounds per year, and lose ½ pound lean tissue per year
These changes can only be detected by assessing body composition periodically
To make valid comparisons, use the same technique for both pre- and post-program assessments

28. Body Composition Changes
Figure 4.9. Typical body composition changes for adults in the United States.

29. Assess Yourself
Have you been able to maintain your body weight at a stable level during the past 12 months?
Do you understand the following concepts?
Body composition vs. body weight
Recommended body weight
Techniques for assessing body composition
Effects of BMI and waist circumference on risk for disease