Body Composition & Weight Management Flashcards
Rationale for Body Comp Assessment
- Indicates many chronic diseases
- Detection of obesity
- Its development are of primary importance for many health and exercise science professionals
- Assessment of muscle mass
- Bone density
Chronic Diseases indicated by Body Comp Assessment
- Type 2 diabetes
- Hypertension
- Hyperlipidemia
- Metabolic syndrome
- CAD
- Certain types of cancer
Assessment of Muscle Mass (Rationale for Body Comp Assessment)
- LBM
- Muscle wasting (sarcopenia)
Bone density (Rationale for Body Comp Assessment)
Risk of osteoporosis
Selection of Methodology for Body Comp Assessment
- There are no direct in vivo methods
- Cost
- Availability
- Technician training
- Individual characteristics
- Performance requirements
Criticism of BMI (Health Risk Assessments)
- Poor predictor of % body fat
- Results in inaccurate classifications for some individuals
- SEE + 5% for predicting % body fat
For non-athletic population Health Risk Assessments are…
Reasonably accurate
Therefore, BMI meets the… (Health Risk Assessments)
Objectives of assessing health risk
Direct Body Comp Method
- Chemical analysis of the whole body or cadaver
- Not suitable for living human body comp assessment
Indirect Body Comp Method
- Derived from the direct method of chemical analysis
- Hydrodensitometry
Doubly Indirect Body Comp Method
- Derived from an indirect method
- Generally prone to greater error in measurement
- Skinfold analysis
Property-Based Methods (Indirect Methods)
- Measurement of body volume
- Decay properties of specific isotopes
- Electrical resistance
- Estimation of total body water (TBW) from tritium dilution (most common)
Component-Based Methods (Indirect Methods)
- The measured quantity is first assessed using a property-based method and
- The component is estimated by application of the model
- FFM can be estimated from body water by use of tritium dilution to measure TBW
Body Fat Prediction Equation Selection
- To whom is the specific % body fat equation used applicable?
- Was an appropriate compartment model used to develop the equation used?
- Was a representative sample of the population studied?
- How were the predictor variables measured?
- Was the equation cross-validated in another sample of the population?
- Does the equation give accurate estimates of % body fat?
General Error Concepts in Body Comp Assessment
No method is perfect; Error is expressed as the + SEE
+ 1 SEE refers to 68% of population
SEE is a measure of the variability of a population’s actual % BF values
Example of General Error Concepts in Body Comp Assessment
-68% of similar individuals (16.5 to 23.5%)
-32% have % BF values > + 3.5%
=< 16.5% or > 23.5%
Skinfold Analysis
- Considered a doubly indirect method
- Based on 2C model
- Based on the principle that amount of subcutaneous fat is directly proportional to the total amount of BF
- Specific skinfold regression equation used must match population measured
However, proportion of subcutaneous fat to total fat varies with… (Skinfold Analysis)
Gender, age, race and other factors
Limitations of Skinfold Analysis
- Technician training
- Skinfold site measurement accuracy
- Measurement technique
Bioelectrical Impedance Analysis (BIA)
Noninvasive and Easy-to-administer
Basic Premise of Bioelectrical Impedance Analysis (BIA)
Mass of FF tissue is proportional to the electrical conductivity of the body; LBM is good electrical conductor
Fat is poor conductor (Bioelectrical Impedance Analysis (BIA)
Impedes electrical current
Uses equations for % BF (3C model) using assumptions about
Bioelectrical Impedance Analysis (BIA
- Hydration levels
- Exact water content of various tissues
Factors affecting BIA (Bioelectrical Impedance Analysis (BIA)
-Fluid intake Meal timing Bladder fullness Diuretic or Caffeine use Recent exercise
Make sure person is of normal hydration (Bioelectrical Impedance Analysis (BIA)
-SEE is b/t + 3.5-5.0%
% BF consistently (Bioelectrical Impedance Analysis (BIA)
- Overestimated for lean people
- Underestimates obese people
Near-Infrared Interactance
- Based on principle of light absorption
- Reflection using near-infrared spectroscopy to provide info about the chemical composition of body
- A light wand device is positioned on a body part
- Absorption of the infrared beam is measured
- SEE reported > + 5.0%
Major limitation of Near-Infrared Interactance
Relatively small sampling area on body
Hydrostatic Weighing
- Considered criterion or gold standard
- Based on Archimede’s principle
- Can determine body density
How to determine body density from Hydrostatic Weighing
Db = mass/volume
-Db is then converted to % BF using 2C model equation
What must you know for Hydrostatic Weighing
- Residual volume
- Density of water
- Trapped gas in GI tract
- Dry body weight
- Body weight fully submerged in water
Density of lean tissue for Hydrostatic Weighing is assumed to be
- 1.10 g·cc-1 for all
- African Americans > 1.11 g·cc-1
- Youths <1.09 g·cc-1
- SEE about + 2.5%
Major limitations of Hydrostatic Weighing
- Space
- Plumbing
- Cost
- Specialized equipment
- Time
- Need for an accurate RV
- Inherent fear many adults have in staying fully submerged
Clinical Assessment Procedures
- Computed tomography (CT)
- Magnetic resonance imaging (MRI)
- Non-invasively quantify volume of body tissue (such as fat)
- Use multicompartment model
- Can analyze muscle & bone density too
- Can be high cost
- Not very practical
Plethysmography: Air Displacement
- Body volume measured by air displacement rather than water displacement
- Bod Pod uses a dual chamber plethysmograph that measures body volume
- Changes in air pressure with a closed 2C chamber
- SEE varies from + 2.2-3.7%
- Can be expensive
- Must wear tight fitting clothes
Dual-Energy X-ray Absorptiometry
- Based on 3C model
- Used to assess total bone mineral content and estimate bone, fat, and lean tissue
- Uses low-level radiation
- Is safe, fast & accurate
- Generally large and expensive
- Precision about 1% with an SEE of about 1.8% BF
3C model of Dual-Energy X-ray Absorptiometry
- Total body mineral stores
- Mineral-free lean mass
- Fat mass
Although national standards have been developed and accepted for BMI and WHR
None exist for estimates of % BF
All standards for BF differ by…
- Gender
- Most by age
Body fat % standards from research revisions (1994) evaluated college-educated men and women
- Average college-aged male: 12-15%
- Average college-aged female: 22-25%
Essential Fat: Women (Body fat % standards)
8-12%
Athletic: Women (Body fat % standards)
12-22%
Minimal: Women (Body fat % standards)
10-12%
Recommended (over 56yrs): Women (Body fat % standards)
25-38% (obese = anything greater)
Recommended (35-55yrs): Women (Body fat % standards)
23-38% (obese = anything greater)
Recommended (34yrs or less): Women (Body fat % standards)
20-35% (obese = anything greater)
Essential Fat: Men (Body fat % standards)
3-5%
Athletic: Men (Body fat % standards)
5-13%
Minimal: Men (Body fat % standards)
5%
Recommended (over 56yrs): Men (Body fat % standards)
10-25% (obese = anything greater)
Recommended (35-55yrs): Men (Body fat % standards)
10-25% (obese = anything greater)
Recommended (34yrs or less): Men (Body fat % standards)
8-22% (obese = anything greater)
