Body Composition

 Refers to the relative amounts of the different compounds in the body. Fat mass Fat-free mass  Why Study Body Composition? Overweight vs. Over fat vs. Obesity Risk for various diseases Monitor change from an intervention Some job requirements involve body composition standards Athletic/sports prowess

 Fat-free mass is composed of all of the body's nonfat tissue including bone, muscle, organs, and connective tissue.  Lean body mass includes all fat-free mass along with essential fat. Lean body mass is difficult to measure so the fat mass/fat-free mass model is most often used.

Body composition is a better indicator of fitness than body size and weight. Being overfat (not necessarily overweight) has a negative impact on athletic performance. Standard height-weight tables do not provide accurate estimates of what an athlete should weigh because they do not take into account the composition of the weight. An athlete can be overweight according to these tables yet have very little body fat.

 Body build is the form or structure of the body. Muscularity (mesomorphy) Linearity (ectomorphy) Fatness (endomorphy)  Body size is determined by height and weight.

ENDOMORPHYMESOMORPHY ECTOMORPHY

Different Levels of BC Measurement

This is the historical/traditional system for body composition assessment and quantification. Lean Body Mass ( more accurately the FFBM) Fat Body Mass The two component system has the following assumptions: 1. Fat density = 0.90 g/mL at 37°C 2. LBM density = 1.10 g/mL at 37°C 3. All individuals have the above mass densities 4. LBM is 73.8% water, 19.4% protein, and 6.8% mineral

Hydrodensitometry Air-displacement plethysmography (BodPod™) Hydrodensitometry (underwater weighing or hydrostatic weighing) Has been termed the “gold standard” of body composition assessment. However, inadequacies of the assumptions can cause errors as large as ±4% fat. This method is based on Archimedes’ principle, where a person’s weight underwater is used to calculate body volume. Body density is then calculated, and specific equations are used that convert body density into %fat.

 More common techniques  Hydrostatic weighing  Air displacement – Bod Pod  Skinfold thickness  Girth measurements  Bioelectrical impedance

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Body Density (Db) = body mass (g) / body volume (mL) Db = Wa / {[(Wa - Ww) / Dw] - (RV mL)} where; Db = body density (g/mL) Wa = body mass out of water Ww = body mass underwater Dw = density of water (g/mL) RV = residual lung volume (mL) Siri Equation - % body fat = [(4.95 / Db) ] x 100 Brozek Equation - % body fat = [(4.57 / Db) ] x 100

 Research/medical facility techniques  Dual energy X-ray absorptiometry (DEXA)  Magnetic resonance imaging (MRI)  Computed tomography (CT)  Total body electrical conductivity (TOBEC)

 Dual energy X-ray absorptiometry (DEXA)  Frequently used by research and medical facilities  Considered by many as the standard technique for body composition assessment  Uses low-dose beams of X-ray energy  Measures fat mass, fat distribution pattern, and bone density  Procedure is simple; takes only 15 minutes to administer  Not readily available to most fitness participants _KuB-0&feature=related

 Individual sits inside small chamber  Computerized pressure sensors determine the amount of air displaced by the person  Body volume is calculated by subtracting the air volume with the person inside the chamber from the volume of the empty chamber (air in the lungs is taken into consideration)  Body density and percent body fat are then calculated  Less cumbersome to administer  Takes only about 5 minutes e.com/watch?v=el obnbT33yo

 Based on the principle that approximately half of the body’s fatty tissue is directly beneath skin  Reliable measurements of this tissue give a good indication of percent body fat  Skinfold test is done with pressure calipers  Several sites are measured and percent fat is estimated from the sum of the three sites using  All measurements should be taken on the right side of the body

Chest Abdomen Triceps Suprailium Thigh

Girth Measurements sites: Below are some common sites used for girth measurements.  head  neck  arm-relaxed  arm-flexed  forearm  wrist  chest  waist  hip  thigh (gluteal)  thigh (mid)  calf  ankle

 Simpler to administer, but accuracy is questionable  Sensors are applied to the skin and a weak electrical current is run through the body to estimate body fat, lean body mass, and body water  Based on the principle that fatty tissue is a less-efficient conductor of an electrical current  Fat – ______ current  Muscle – ______ current ch?v=FaczpaAxims

The ratio of mass to height 2 BMI = body mass (kg) / body height (m) 2 ; for example: BMI = 80 (kg) / (1.72) 2 (m) = kg/m2 1 inch = meters BMI < 20.0 is considered underweight A BMI > 30 is associated with greater prevalence of mortality from heart disease, cancer, and diabetes

 Even though the risk for premature illness and death is greater for those who are overweight, the risk also increases for individuals who are underweight

 Predicts disease risk according to the way people store fat (waist versus other areas) Disease Risk according to WC

 Predicts disease risk according to “apple” or “pear” shape Disease Risk according to Waist-to-Hip Ratio

 Disease risk increases with total waist measurement of more than  40 inches for men  35 inches for women  Disease risk increases with total waist-to-hip measurement above  0.94 for young men  0.82 for young women

Because of the typical reduction in physical activity, each year the average person gains 1.5 lbs of body fat and loses a half a pound of lean tissue

 Loss of lean body mass can be offset or eliminated by combining a sensible diet with physical exercise

The weight that would result from desired values for FBM and FFBM: for example: Fat weight = current weight (kg) x (% fat/100) Lean Body Mass = current weight (kg) - fat weight Ideal weight = LBM / [1 - (% fat desired / 100)] Desirable fat loss = current weight - ideal body weight

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