1. Body Composition Assessment
A description of assessment methods.

2. Learning Objectives
Differentiate among body build, body size, and body composition.
Discover how densitometry and several field techniques are used to assess body composition.
Find out what tissues of the body constitute fat-free mass

3. Learning Objectives
Calculate changes in FW and FFW with a weight loss program
Find out what guidelines best determine an subject's goal weight.

4. Body Composition
The relative % of body weight that is fat and fat-free tissue

5. Why measure body comp? Health Implications Make BW recommendations
there is an ideal % fat for health reasons (prevent onset of diabetes, CHD, BP, etc…)
Make BW recommendations
can use % fat values to determine an ideal BW
how much fat to lose versus how much muscle to gain

6. Why measure body comp? Describe Athletic Populations
swimmers are more fat (fat floats)
wrestlers/gymnasts want less fat
endurance runners don’t want massive amounts of muscle but power lifters do

7. Height - Weight Tables
Body composition is a better indicator of fitness than body weight/height. Being overfat (not necessarily overweight) has a negative impact on exercise/athletic performance. Standard height-weight tables do not provide accurate estimates of what you should weigh because they do not take into account the composition of the weight. A subject can be overweight according to these tables yet have very little body fat.

8. For example: Body Builder: 5’5” 200 pounds
overweight according to height/weight tables
4% body fat
ALL MUSCLE!!!

9. Fat Mass vs. Fat-free Mass
Two Component Model
Fat-free mass is composed of all of the body's nonfat tissue including bone, muscle, organs, and connective tissue. Fat mass includes all the body’s fat along with essential fat.

10. Assumptions of Two-Component Models
1. The density of fat is g/ml
2. The density of FFM is g/ml
3. The densities of fat and FFM are the same for all individuals

11. Assumptions
4. The densities of the various components of FFM are constant within an individual
5. The individual being measured differs from a reference body (73.8% water, 19.4% protein, 6.8% mineral) only in the amount of fat

12. Fat Depots 1. Subcutaneous 2. Intermuscular 3. Intramuscular
4. Abdominal and Thoracic Cavity

13. MODELS OF BODY COMPOSITION

14. Essential Fat All fat is not bad!!
We need fat for padding of organs, insulation, energy source
There is a minimum amount that we need to function daily = essential fat
Gender specific
males ~ 3%
females ~ 7%

15. Essential Fat Why the differences?
A male at 7% is like a female at 17%
Women are more complicated!!
Women have babies, menstrual cycles, etc… and need more fat for the survival of the species

16. Other Models
We can’t distinguish between fat that is essential and fat that is not so in order to have more components in a model:
we break the fat-free mass down further (referred to as a multi-component model)
ie., 3-component model (fat, water, solids)
ie., 4-component model (fat, water, mineral, protein)

17. Methods 1. Under Water Weighing (Hydrodensitometry)
2. Bioelectrical Impedance (BIA)
3. Dual-Energy X-ray Absorptiometry (DEXA)
4. Near-Infrared Interactance (NIR)

18. Methods
Anthropometric Measures (anthro=body; metric=measuresbody measurements)
5. Skinfolds
6. Circumference (WHR)
7. Diameters (body typing)
8. Height (BMI)
9. Others…..??

19. Hydrodensitometry
Used to be considered the most accurate (up for debate now that DEXA is used)
+2.5% if done with experienced subjects
Considered a lab technique (can’t carry your tank with you out into the field)
Two-component Model

20. UWW Fat Component - Fat (adipose)+Neural+Essential Fat
density of 0.9 g/ml
Fat-Free Component - muscle+bones+ tendons+organs
density of 1.10 g/ml

21. UWW
Water Density ~ 1.0 g/ml (temperature of the water affects the density)
Thus, if more fat  will float (fat is less dense than water)
If more muscle  will sink (muscle is more dense than water)

22. Hydrodensitometry BD = BW/BV Body weight = measured on a regular scale
Body volume = measured using hydrostatic (underwater) weighing accounting for water density and air trapped in lungs

23. UWW
Body Density = BW÷((BW-UWW)/H20 Density) - RV-0.1

24. UWW Determine BV  Calculate BD  Calculate %fat
If have high BV  low BD  more fat
If low BV  high BD  less fat

25. UWW
Archimedes principle - an object (or human) immersed in fluid, loses an amount of weight equivalent to the weight of the fluid that is displaced
More simply - fill a bathtub with water - submerge - if catch all the water that spills over and weight it = BV

26. Procedures 1. Wear light clothing (swimsuit)
2. Use bathroom prior to weighing
3. Calibrate scale
4. Weight the chair or seat and equipment
5. Measure water temp
6. Remove all air from clothing

27. Procedures 7. Sit in seat 8. Submerge
9. Blow all air out of lungs and remain still
trials; average of the highest three
11. Subtract weight of apparatus from average UWW

28. UNDERWATER WEIGHING TECHNIQUE

29. Residual Volume
Cannot blow all of the air out of your lungs (that would be bad!!)
We need to account for the air that is left in the lungs (RV) + the air in the GI (~0.1L)

30. Determining RV
Prediction equations based on height and/or Vital Capacity
Male = 0.24 x VC
Female = 0.28 x VC
Male = 0.019(Ht cm) (age)-2.24
Female = 0.023(Ht cm)+0.021(age)-2.978
Nitrogen Analysis (rebreathing apparatus)

31. Equations
Inaccuracies in hydrodensitometry are due to variation in the density of the fat-free mass from one individual to another. Age, sex, and race affect the density of fat-free mass.
Thus, we have age/gender/race/fat specific equations - Table 4-1 Guidelines

32. Equations % fat = 4.57÷BD - 4.142 * 100 ACSM guidelines:

33. Advantages Accurate if done correctly
Many equations that are specific to each group

34. Disadvantages Most subjects not comfortable blowing all their air out
especially hard for children to understand
methods to compensate for this
Ambulatory problems (ie., elderly) getting into a pool/tank
Some people just do not like water

35. Sources of Error Not getting all air out Reading scale wrong
Are not using the correct equation
Estimation of RV

36. BIA
Based on the premise that fat-free tissue is a better conductor of an electrical current (contains water and electrolytes) than fat tissue
The resistance to current flow is inversely related to FFM

37. Assumptions
1. The human body is a perfect cylinder with uniform length and cross-sectional area
2. The impedance to a current is directly related the length of the conductor and inversely related to its cross-sectional area

38. Assumptions
3. Biological tissues act as conductors or insulators, and the flow will follow the path of least resistance
4. Impedance is a function of resistance and reactance (opposition to flow caused by the capacitance of a cell membrane)

39. BIA Abstain from eating or drinking for 4 hours prior
No exercise 12 hours prior
No alcohol 48 hours prior
No diuretics (caffeine) prior to assessment

40. Equations
Each machine has its own equation (developed by the manufacturer and is proprietary)
%fat = 4.57 ÷ ( ((BW * Resistance) ÷ Ht2)) * 100
ht = length of the conductor

41. BIA Reseach Equations
Population-specific equations have been developed through research
Used for children, different races, different ages etc… (p. 161)
May have better accuracy than machine equations

42. Advantages Non-invasive Safe Easy to administer
Accurate on some populations
Field technique

43. Advantages More costly than SF calipers
Many studies have begun to cross-validate (just because the equation worked on the researchers population doesn’t mean it will work on others)
Beginning to develop specific equations
get resistance value from machine and enter into a specific equation

44. Disadvantage The accuracy has been questioned:
Skinfolds 2.4 % error
BIA 5% error
Visual 3.1% error
Race cannot be entered into the machine
Children distribute water differently than adults

45. DEXA 3 component model assesses total bone mineral content
bone, fat, fat-free mass
assesses total bone mineral content
usually found in a clinical setting

46. Advantages Accurate Measurement of bone content (osteoporosis) safe
rapid
minimal subject cooperation (just lay there)

47. Disadvantage
Costly
Limited Access

48. NIR
Based on the premise that the degree of infrared light absorption is related to the composition of the substance through which light passes
Fat and Fat-Free Mass absorb and reflect light differently

49. NIR
Emit infrared light at wavelengths of nm into a body part (ie., biceps) and measures the intensity of the re-emitted light
More specific equations/machines are necessary

50. Advantages
Non-invasive
Safe
Easy to administer
Field technique

51. Disadvantages Cost? Is it worth it? Few Age/Gender Specific Equations
Accurate?
Futrex %
Futrex 5000A 6.3%
Futrex %
Sum
BIA %

52. Skinfolds
Measurement of subcutaneous adipose tissue at specific anatomical sites
BD or %fat is obtained with the use of equations (either population specific or generalized)

53. SF Procedures Take all measurements on the right side of the body
Identify and mark site
Grasp skin and fat between thumb and index finger 1cm above marked site
Continue grasping at the site while taking the measurement

54. SF Procedures
Place the jaws of the caliper perpendicular to the fold and slowly release the pressure
Take the measurement 4 seconds after pressure is released
Read the dial of the nearest 0.1mm (Harpenden or Holtain), 0.5mm (Lange), or 1mm (plastic)

55. SF Procedures
Take at least 2 non-consecutive measurements - if values vary by +10% take additional measurements
No measurements directly after exercise
Reliability should be 0.95 or greater

56. Sites Chest Subscapular Midaxillary Suprailiac Abdominal Triceps
Biceps
Thigh
Calf

57. Equations Jackson’s 3-site
Males - BD= (sum3) (sum3) (age)
chest, abdomen, thigh
Females - BD= (sum3) (sum3) (age)
triceps, suprailiac, thigh

58. Waist to Hip Ratio Indication of the pattern of body fat distribution
Indicator of the health risks of obesity
excess trunk fat - increased risk of hypertension, type 2 diabetes, high cholesterol, CAD, premature death

59. Waist to Hip Ratio Risks increase with increasing ratios
very high risk >0.94 young men and 0.82 young women
very high risk >1.03 older (60-69 years) men and 0.90 for older women

60. Measurements Made with a tape measure
Waist - at the narrowest part of the waist between the umbilicus and xiphoid process
Hips - biggest part of the gluteals

61. Body Mass Index (BMI)
Ratio of a person’s weight (kg) to the height squared (m2)
Used to categorize people with respect to their degree of obesity
Not used to determine % fat

62. BMI 20-25 kg/m2 - desirable 25-29.9 kg/m2 - overweight
> obesity