Illinois State University Introduction to Body Composition Chapter 1

Illinois State University

Introduction to Body Composition

Chapter 1


Exercise and Body Composition

Body composition refers to the substances that make up the body.

This includes more than just fat.



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


Why do we measure body composition?

Health Performance Insurance


Reasons for Assessing Body Composition*

To identify a client’s health risk associated with excessively low or high levels of total body fat.

To promote a client’s understanding of health risks associated with too little or too much body fat.


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.



To estimate a healthy body weight for a client.

To formulate dietary recommendations and exercise programs.



To monitor growth, development, maturation, and age-related changes in body composition.

• (Heyward and Wagner, 2004)


Why we do not measure BC?

Grading purposes Stereotyping Labeling Criticism


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


Key Terms

Reference method Percent body fat Total body bone

mineral

Total body mineral Total body water



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


Key Terms

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


Assessment of Body CompositionAssessment of Body Composition

Mirror Fit of Clothes Social Feedback Weight


Anthropometric TechniquesAnthropometric Techniques

Height vs Weight Body mass index (BMI) = kg/m2

Girth and breadth - circumferences Skinfold measurements


Body Comp AssessmentBody Comp Assessment

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

(Bod Pod).


Body Comp AssessmentBody Comp Assessment

Computer assisted tomography


Body Composition

Most methods estimate percent body fat from body density.

Most body density estimations are drawn from a relatively small population of cadavers.



Metropolitan Life Insurance Tables– Used to establish insurance premium– Based on relationship between height and

weight.


Body Composition Models

See Fig 1.1



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



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



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



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



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.



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



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.



Potential problems?


Models

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


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.


2-C Model

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


2-C Models

The 1963 Brozek model uses:

%BF = (4.57/Db - 4.142) x 100


2-C Models

The 1956 Siri model uses:

%BF = (4.95/Db - 4.50) x 100


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).


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.


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.


2-C Models

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


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


Assumptions

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


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


Body DensityBody 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.


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


Which technique should be used?Which technique should be used?

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


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.


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.


Overweight and Obesity (BMI)

III> 40

II35-39.9

I30-34.9Obesity

25-29.9Overweight

18.5-24.9Normal Weight

<18.5Underweight

Obesity ClassBMI (kg/m2)

WHO 1998


Standards of FatnessStandards of Fatness

Men Women

Underfatness <3 <12

Essential Fat 3 12

Optimal Health 3-20 12-30

Overfatness 20-25 30-35

Obesity >25 >35


Current Body Wt

Goal % Fat*

Goal % LBM*

Current % Fat*

Current Fat Wt

Current LBM

Target Body Wt

1

* % is expressed as a decimal. Divide by 100 before entering the data.

X byminus

minusComputing Target Wt assuming all wt. Loss is fat

Fill in boxes with double lines and compute others

Documents

Illinois State University Introduction to Body Composition Chapter 1