Body Composition Chapter 4 Body Composition The relative

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Body Composition Chapter 4 .

Body Composition Chapter 4 .

Body Composition • The relative proportion of fat and fat-free tissue in the body

Body Composition • The relative proportion of fat and fat-free tissue in the body • Body composition is not determined by body weight per se, but what the weight is composed of • Most commonly uses the 2 -compartment model

Confusing Terminology • Overweight- deviation in body weight from some standard in relation to

Confusing Terminology • Overweight- deviation in body weight from some standard in relation to height • Overfat- body fat greater than some standard (BMI ≥ 25) • Obesity- higher amounts of fat that detrimentally affects health (BMI ≥ 30)

Health Consequences of Obesity • • Coronary Heart Disease Hypertension Type II Diabetes Hyperlipidemia

Health Consequences of Obesity • • Coronary Heart Disease Hypertension Type II Diabetes Hyperlipidemia Cancers Orthopedic problems Poor self-image

Body Composition Terminology • Fat weight (FW)- total fat amount in pounds • %

Body Composition Terminology • Fat weight (FW)- total fat amount in pounds • % fat- percentage of total body weight that is fat weight • Fat-free weight (FFW) – total fat-free tissue in pounds • % fat-free- percentage of total body weight that is fat-free tissue

Fat Weight + Fat-Free Weight = Body Weight % Fat + % Fat Free

Fat Weight + Fat-Free Weight = Body Weight % Fat + % Fat Free = 100%

Computational Example • Weight = 200 lbs; % fat = 20%; • Fat Weight

Computational Example • Weight = 200 lbs; % fat = 20%; • Fat Weight = 200 x. 20 = 40 lbs • Fat-Free Weight = 200 - 40 = 160 lbs

Computing Ideal Weight • Ideal Weight = FFW / Ideal % FFW • Example

Computing Ideal Weight • Ideal Weight = FFW / Ideal % FFW • Example – Body Wt = 180; %fat = 20%; What is ideal body weight at 10% fat? – FW = 180 lbs x. 20 = 36 lbs – FFW = 180 - 36 = 144 lbs – IBW = 144 /. 90 = 160 lbs

Components of Fat-Free Weight • Muscle • Bone • Organ Systems

Components of Fat-Free Weight • Muscle • Bone • Organ Systems

Components of Fat Weight • Essential Fat – most is non-visible – associated with

Components of Fat Weight • Essential Fat – most is non-visible – associated with deeper body structures • Non-essential or Storage Fat – Beneath the skin and visible – Adipose tissue fat

Gender Differences In Body Fatness Gender Differences in Body Composition Male Body Weight 170

Gender Differences In Body Fatness Gender Differences in Body Composition Male Body Weight 170 % Fat 15 Essential Fat 3% Non –Essential 12% Fat Female 130 25 12% 13%

Gender Differences • Females are proportionately fatter than males (as % of body mass)

Gender Differences • Females are proportionately fatter than males (as % of body mass) – Female sex hormones promote fat deposition – Male sex hormones promote muscle growth • Most of the female’s increase in fatness is due to an increase in the essential fat stores • Males and females have similar levels of nonessential fat

Quantification of Body Composition • • Height/Weight Ratio Body Mass Index (BMI), Quetelet Index

Quantification of Body Composition • • Height/Weight Ratio Body Mass Index (BMI), Quetelet Index Body density or % fat Waist to Hip Ratio

Height/Weight Ratio • Subjective measure • Assumes an average proportion of weight is fat

Height/Weight Ratio • Subjective measure • Assumes an average proportion of weight is fat • May incorporate frame size • Not a very desirable method

Body Mass Index • Weight/Height 2 ; kg/meters 2 • Extensively used in epidemiology

Body Mass Index • Weight/Height 2 ; kg/meters 2 • Extensively used in epidemiology studies • Most commonly used measure to define obesity • Does not measure fatness

Problems With BMI • • Weight = 280 lbs Height = 77 inches %fat

Problems With BMI • • Weight = 280 lbs Height = 77 inches %fat = 30% (obese) BMI = 33 (obese) • • Weight = 280 lbs Height = 77 inches %fat = 15% (healthy) BMI = 33 (obese)

Waist/Hip Ratio • Waist circumference/Hip circumference • Waist- smallest circumference between the umbilicus and

Waist/Hip Ratio • Waist circumference/Hip circumference • Waist- smallest circumference between the umbilicus and xiphoid process • Hip – largest circumference around the buttocks • Implication is that as waist get bigger there is more abdominal storage fat

Density and % Fat • Hydrodensitometry – (Underwater Weighing) – Hydrostatic Weighing • Air

Density and % Fat • Hydrodensitometry – (Underwater Weighing) – Hydrostatic Weighing • Air Displacement Plethysmography • Anthropometry – Skinfolds – Circumferences & Diameters • Bioelectrical Impedance

Hydrodensitometry (UWW) • Measures body volume using Archimedes' principle • Loss of weight in

Hydrodensitometry (UWW) • Measures body volume using Archimedes' principle • Loss of weight in water is equal to the weight of the volume of water displaced • Density = mass or weight/volume

 • Advantages of Hydrodensitometry – One of the most accurate methods • Disadvantages

• Advantages of Hydrodensitometry – One of the most accurate methods • Disadvantages of Hydrodensitometry – Very subject dependent – Takes 15 minutes – Requires the ability to submerge subject under water – High skill required of technician

Plethsmyography (Bod Pod) • Body volume is determined by using Boyle’s Law – volume

Plethsmyography (Bod Pod) • Body volume is determined by using Boyle’s Law – volume is inversely proportional to pressure. • Bod Pod measures pressure differences. • Density = mass or weight/volume

 • Advantages of Plethysmography – Good accuracy – Little requirement from subject so

• Advantages of Plethysmography – Good accuracy – Little requirement from subject so good for children and older adults – Takes 5 minutes – Low skill required of technicial • Disadvantages of Plethysmography – Cost of equipment is $30, 000

Skinfolds • Based on the principle that subcutaneous fat at various locations (ie. The

Skinfolds • Based on the principle that subcutaneous fat at various locations (ie. The skinfolds) is predictive of total body fatness • Most equations use at least 2 skinfolds • Generally, the more skinfolds the more accurate the prediction of body fatness

 • Advantages of Skinfolds – Subject has to do little – Many specific

• Advantages of Skinfolds – Subject has to do little – Many specific equations are available – Cost effective – Only takes 2 -3 minutes – Moderate accuracy • Disadvantages of Skinfolds – High technical skill required

Bioelectric Impedance Analysis (BIA) • Measures the resistance to a small electrical current introduced

Bioelectric Impedance Analysis (BIA) • Measures the resistance to a small electrical current introduced into the body (Impedance) • Once the impedance is determined then body water is determined. • Principle is that water is a good conductor and fat is a poor conductor of the electrical current. – More resistance = less body water = more fat – Less resistance = more body water = more muscle

 • Advantages of BIA – Subject has to do little – Only need

• Advantages of BIA – Subject has to do little – Only need access to hand foot – Equipment is relatively inexpensive- $2000 – Moderate accuracy • Disadvantages of BIA – Highly dependent on hydration status

Interpreting % Fat Values • All methods of measuring % fat have a certain

Interpreting % Fat Values • All methods of measuring % fat have a certain amount of inaccuracy! This inaccuracy is determined by the Standard Error of Estimate (SEE). • The SEE tells you the amount of deviation from the true % fat you can expect from a particular method.

 • There is a 67% probability that the true % fat is within

• There is a 67% probability that the true % fat is within + or - one SEE from the measured value. • Example: Measure % fat = 20%; SEE = 3 % units of body fat There is a 67% probability that the true % fat is between + or - one SEE or 3 % units of fat. or between 17 - 23 %.

 • There is a 95% probability that the true % fat is within

• There is a 95% probability that the true % fat is within + or - two SEE from the measured value. • Example: Measured %fat = 20% SEE = 3 % There is a 95% probability that the true %fat is within + or - two SEE or 6% of the measured value or 14 - 26 %.

SEE of Common Methods • • UWW – 1. 5 -2. 5% Plethysmography –

SEE of Common Methods • • UWW – 1. 5 -2. 5% Plethysmography – 2. 2 -3. 7% Skinfolds – 3 -4% Bioelectric Impedance – Whole Body – 3 -4% – Segmental – 4 -6%

Healthy Values for %Fat • Reasonable & Healthy %fat Range – Males: 10 -

Healthy Values for %Fat • Reasonable & Healthy %fat Range – Males: 10 - 20% – Females: 15 - 30%

Computing UWW WT in air (kg) BD = Wt in air – WT in

Computing UWW WT in air (kg) BD = Wt in air – WT in H 2 O Density H 2 O - RV (L) +0. 1

Converting Density to % Fat Siri Equation 495 %fat = Density - 450

Converting Density to % Fat Siri Equation 495 %fat = Density - 450