Post on 31-Dec-2015
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Introduction to Body Composition
Chapter 1
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Exercise and Body Composition
Body composition refers to the substances that make up the body.
This includes more than just fat.
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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
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Why do we measure body composition?
Health Performance Insurance
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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.
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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.
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Reasons for Assessing Body Composition
To estimate a healthy body weight for a client.
To formulate dietary recommendations and exercise programs.
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Reasons for Assessing Body Composition
To monitor growth, development, maturation, and age-related changes in body composition.
• (Heyward and Wagner, 2004)
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Why we do not measure BC?
Grading purposes Stereotyping Labeling Criticism
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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
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Key Terms
Reference method Percent body fat Total body bone
mineral
Total body mineral Total body water
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Exercise and Body Composition
Key terms related to fatness:– Overweight and underweight– Weight loss and fat loss– Overfat and underfat– Obese
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Key Terms
Obesity may be defined as an excessive amount of body fat relative to body weight.
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Assessment of Body CompositionAssessment of Body Composition
Mirror Fit of Clothes Social Feedback Weight
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Anthropometric TechniquesAnthropometric Techniques
Height vs Weight Body mass index (BMI) = kg/m2
Girth and breadth - circumferences Skinfold measurements
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Body Comp AssessmentBody Comp Assessment
Hydrostatic (underwater) weighing. Bioelectrical Impedance Analysis Air-Displacement Plythesmography
(Bod Pod).
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Body Comp AssessmentBody Comp Assessment
Computer assisted tomography
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Body Composition
Most methods estimate percent body fat from body density.
Most body density estimations are drawn from a relatively small population of cadavers.
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Exercise and Body Composition
Metropolitan Life Insurance Tables– Used to establish insurance premium– Based on relationship between height and
weight.
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Body Composition Models
See Fig 1.1
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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).
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Exercise and Body Composition
The LBM includes essential lipids associated with the brain, nerves, membranes, etc.
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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
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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.
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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.
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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.
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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.
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Exercise and Body Composition
Potential problems?
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Models
This has led to the 4-C molecular level model being the desired model for research purposes– Fat– Mineral (Bone)– Protein (Muscle)– Water
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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.
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2-C Model
The two most common 2-C models rely on estimating percent fat from body density.
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2-C Models
The 1963 Brozek model uses:
%BF = (4.57/Db - 4.142) x 100
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2-C Models
The 1956 Siri model uses:
%BF = (4.95/Db - 4.50) x 100
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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).
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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.
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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.
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2-C Models
For individuals with more than 30% BF, the Siri equation gives relatively higher body fat estimates than the Brozek equation.
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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
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Assumptions
The individual being measured differs from the reference body only in the amount of body fat (triglyceride) or obesity (adipose) tissue.
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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
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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.
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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
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Which technique should be used?Which technique should be used?
Purpose of assessment. Accuracy required. Time required. Availability of equipment. Training of personnel. Expense.
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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.
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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.
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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
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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
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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