Introduction to Body Composition

1
Introduction to Body Composition

• Chapter 1

2
Exercise and Body Composition

• Body composition refers to the substances that
  make up the body.
• This includes more than just fat.

3
Exercise and Body Composition

• The major components of the body for this class
  are
• Muscle mass (protein)
• Bone mass (mineral)
• Fat mass
• Water volume
• Known as the 4-C molecular level model

4
Why do we measure body composition?

• Health
• Performance
• Insurance

5
Reasons for Assessing Body Composition

• To identify a clients health risk associated
  with excessively low or high levels of total body
  fat.
• To promote a clients understanding of health
  risks associated with too little or too much body
  fat.

6
Reasons for Assessing Body Composition

• To monitor changes in body composition that are
  associated with certain diseases.
• To assess the effectiveness of nutrition and
  exercise interventions in altering body
  composition.

7
Reasons for Assessing Body Composition

• To estimate a healthy body weight for a client.
• To formulate dietary recommendations and exercise
  programs.

8
Reasons for Assessing Body Composition

• To monitor growth, development, maturation, and
  age-related changes in body composition.
• (Heyward and Wagner, 2004)

9
Why we do not measure BC?

• Grading purposes
• Stereotyping
• Labeling
• Criticism

10
Key Terms

• Adipose tissue
• Body density
• Body mass
• Body volume
• Densitometry
• Dual-energy X-ray absorptiometry
• Essential lipids

• Fat-free body density
• Fat-free mass
• Fat mass
• Healthy body weight
• Hydrometry
• Lean body mass
• Nonessential lipids

11
Key Terms

• Reference method
• Percent body fat
• Total body bone mineral

• Total body mineral
• Total body water

12
Exercise and Body Composition

• Key terms related to fatness
• Overweight and underweight
• Weight loss and fat loss
• Overfat and underfat
• Obese

13
Key Terms

• Obesity may be defined as an excessive amount of
  body fat relative to body weight.

14
Assessment of Body Composition

• Mirror
• Fit of Clothes
• Social Feedback
• Weight

15
Anthropometric Techniques

• Height vs Weight
• Body mass index (BMI) kg/m2
• Girth and breadth - circumferences
• Skinfold measurements

16
Body Comp Assessment

• Hydrostatic (underwater) weighing.
• Bioelectrical Impedance Analysis
• Air-Displacement Plythesmography (Bod Pod).

17
Body Comp Assessment

• Computer assisted tomography

18
Body Composition

• Most methods estimate percent body fat from body
  density.
• Most body density estimations are drawn from a
  relatively small population of cadavers.

19
Exercise and Body Composition

• Metropolitan Life Insurance Tables
• Used to establish insurance premium
• Based on relationship between height and weight.

20
Body Composition Models

• See Fig 1.1

21
Exercise and Body Composition

• The traditional two-component model of body
  composition defines the body in terms of its
  adipose tissue (AT) and lean body mass (LBM).

22
Exercise and Body Composition

• The LBM includes essential lipids associated with
  the brain, nerves, membranes, etc.

23
Exercise and Body Composition

• This model was refined into another two-component
  model based on fat mass (FM) and fat free mass
  (FFM).
• Referred to as 2-C molecular level model

24
Exercise and Body Composition

• The fat includes all extractable lipids contained
  in both adipose tissue and the other tissues, and
  the residual is the fat free mass.

25
Exercise and Body Composition

• A three-component model was then developed with
  the added component being total body water.
• Referred to as the 3-C water molecular level
  model.

26
Exercise and Body Composition

• A problem with all of these models was that one
  had to make assumptions about bone mineral and
  protein stores in the body.

27
Exercise and Body Composition

• These assumptions included that bone has a
  density of about 3.0 gm/ml, compared with about
  1.0 gm/ml for body water, about 1.34 for body
  protein, and about 0.9 for fat.

28
Exercise and Body Composition

• Potential problems?

29
Models

• This has led to the 4-C molecular level model
  being the desired model for research purposes
• Fat
• Mineral (Bone)
• Protein (Muscle)
• Water

30
Models

• However, most assessment still rely on the 2-C
  molecular level model because it is difficult to
  measure the components of the 4-C model.

31
2-C Model

• The two most common 2-C models rely on estimating
  percent fat from body density.

32
2-C Models

• The 1963 Brozek model uses
• BF (4.57/Db - 4.142) x 100

33
2-C Models

• The 1956 Siri model uses
• BF (4.95/Db - 4.50) x 100

34
2-C Models

• The major difference between the models is
• In the Brozek model, any variation in measured Db
  from the reference body density is assumed to be
  due to a difference in obesity (adipose tissue).

35
2-C Models

• In the Siri model, any variation in measured Db
  from the reference body is due to a difference in
  triglyceride content instead of adipose tissue.

36
2-C Models

• However, they both yield nearly identical BF
  estimates (varying by only 0.5-1.0 BF) for
  densities ranging from 1.0300 to 1.0900 g/cc.

37
2-C Models

• For individuals with more than 30 BF, the Siri
  equation gives relatively higher body fat
  estimates than the Brozek equation.

38
2-C Models

• Both rely on the following assumptions
• The densities of the fat and the fat-free body
  components (water, mineral, and protein) are
  additive and are the same for all individuals
• The proportions of water, mineral, and protein in
  the LBM or reference body are constant within and
  between individuals

39
Assumptions

• The individual being measured differs from the
  reference body only in the amount of body fat
  (triglyceride) or obesity (adipose) tissue.

40
Fat-Free Body Composition

• Component Density Fat-free body Reference
  body (g/cc) () ()
• Water 0.9937 73.8
• Mineral 3.038 6.8
• Protein 1.34 19.4
• Fat-free body 1.1 100 84.7
• Fat 0.9007 15.3
• Reference 1.064 100
• body
• From Table 1.3

41
Body Density

• Density has traditionally been defined as 1.10
  gm/ml.
• In young African American males, some studies
  have shown it to be 1.113 gm/ml.
• 8-10 yr old 1.085 gm/ml.

42
2-C Model Problems

• If you deviated from the reference cadaver, the
  ability to predict your percent body fat
  diminished.
• See Table 1.4 (p. 9) for specific equations

43
Which technique should be used?

• Purpose of assessment.
• Accuracy required.
• Time required.
• Availability of equipment.
• Training of personnel.
• Expense.

44
Which technique should be used?

• At present, experts agree that a multi-component
  approach should be used whenever possible,
  especially for development and validation of body
  composition methods and prediction equations.

45
Standards for Comparison

• Vary greatly depending on the source
• See Table 1.2 for percent body fat standards for
  adults, children, and physically active adults.

46
Overweight and Obesity (BMI)
WHO 1998
47
Standards of Fatness

• Men Women
• Underfatness lt3 lt12
• Essential Fat 3 12
• Optimal Health 3-20 12-30
• Overfatness 20-25 30-35
• Obesity gt25 gt35

48
1
minus
Computing Target Wt assuming all wt. Loss is
fat Fill in boxes with double lines and compute
others
Goal Fat
Current Fat
Goal LBM
?by
X
Current Body Wt
Current Fat Wt
Current LBM
Target Body Wt
minus
is expressed as a decimal. Divide by 100
before entering the data.