PRESENTED BY: B.KARTHIK

MODERATOR: MR.A.D.GOPALSWAMI

BODY COMPOSITION AND MEASUREMENT-OBESITY/WEIGHT MEASUREMENT

OBJECTIVES• To have a better understanding of the different models

of body composition

• To differentiate FAT MASS and FAT FREE MASS

• To know about the Essential fat

• To be familiar with the different methods of body size and composition measurement

• To know about the different types of obesity and classification

BODY COMPOSITION• The relative % of body weight that is fat and fat-

free tissue

MODELS OF BODY COMPOSITION

BEHNKE’S REFERENCE MANAND WOMAN MODEL

FAT MASS VS. FAT-FREE MASS

• Fat-free mass is composed of all of the body's nonfat tissue including bone, muscle, organs, and connective tissue.

• Fat mass includes all the body’s fat along with essential fat.

ESSENTIAL FAT

• All fat is not bad!!

• We need fat for padding of organs, insulation, energy source

• There is a minimum amount that we need to function daily = essential fat

• Gender specific

• males ~ 3%

• females ~ 7%

ASSUMPTIONS OF TWO-COMPONENT MODELS

• The density of fat is 0.900 g/ml• The density of FFM is 1.100 g/ml• The densities of fat and FFM are the same

for all individuals• The individual being measured differs from a

reference body (73.8% water, 19.4% protein, 6.8% mineral) only in the amount of fat

• We can’t distinguish between fat that is essential and fat

that is not so in order to have more components in a model:

• we break the fat-free mass down further (referred to as a

multi-component model)

• ie., 3-component model (fat, water, solids)

• ie., 4-component model (fat, water, mineral, protein)

METHODS TO ASSESS BODY SIZEAND COMPOSITION

Two general approaches determine the fat and fat-free components of the human body:

• 1. Direct measurement by chemical analysis or dissection

• 2. Indirect estimation by hydrostatic weighing; anthropometric measurements; and other simple procedures, including body stature and mass

DIRECT ASSESSMENT

Two methods directly assess body composition.

• In one technique, a chemical solution literally dissolves the body into its fat and nonfat (fat-free) components.

• The other direct assessment approach involves physical dissection of fat, fat-free adipose tissue, muscle, and bone. Such analyses require extensive time, meticulous attention to detail, and specialized laboratory equipment and pose ethical questions and legal problems in obtaining cadavers for research purposes.

INDIRECT ASSESSMENT• Many indirect procedures assess body composition. Archimedes’ principle

applied to hydrostatic weighing, also known as underwater weighing and

hydrodensitometry, computes percentage body fat from body density.

• Other indirect procedures to predict body fat use skinfold thickness and girth

measurements, x-ray, total-body electrical conductivity or impedance, near-

infrared interactance (NIR), ultrasonography, computed tomography (CT), air

plethysmography, magnetic resonance imaging (MRI), and dual-energy x-ray

absorptiometry (DXA).

HYDRODENSITOMETRY

• Used to be considered the most accurate (up for debate now

that DEXA is used)

• Considered a lab technique (can’t carry your tank with you out

into the field)

• Fat Component - Fat (adipose)+Neural+ Essential Fat, density

of 0.9 g/ml

• Fat-Free Component - muscle+bones+ tendons+organs, density

of 1.10 g/ml

• Water Density ~ 1.0 g/ml (temperature of the water affects the

density)

• Thus, if more fat - will float (fat is less dense than water)

• If more muscle - will sink (muscle is more dense than water)

• BD = BW/BV

• Body weight = measured on a regular scale

• Body volume = measured using hydrostatic (underwater) weighing

accounting for water density and air trapped in lungs

HYDRODENSITOMETRY

• Body Density = BW÷((BW-UWW)/H20 Density) - RV-0.1

• Determine BV Calculate BD Calculate %fat

• If have high BV low BD more fat

• If low BV high BD less fat

• More simply - fill a bathtub with water - submerge - if catch all

the water that spills over and weight it = BV

RESIDUAL VOLUME

• Cannot blow all of the air out of your lungs (that would be bad!!)

• We need to account for the air that is left in the lungs (RV) + the air in the GI (~0.1L)

• Prediction equations based on height and/or Vital Capacity

• Male = 0.24 x VC

• Female = 0.28 x VC

• Male = 0.019(Ht cm)+0.0115(age)-2.24

• Female = 0.023(Ht cm)+0.021(age)-2.978

• Nitrogen Analysis (rebreathing apparatus)

• Inaccuracies in hydrodensitometry are due to variation in the density of the fat-free mass from one individual to another. Age, sex, and race affect the density of fat-free mass.

• % fat = 4.57÷BD - 4.142 * 100

• ACSM guidelines:

• %fat = 457÷BD - 414.2

WHOLE BODY PETHYSMOGRAPHY

• Measures body volume by air displacement actually measures

pressure changes with injection of known volume of air into

closed chamber

• Large body volume displaces air volume in chamber results in

bigger increase in pressure with injection of known volume of air

• Body plethysmograph or body box.

• Based on Boyle’s Law:

• Pressure of a gas varies inversely with its volume.

• Air volume in the box can be measured.

• When person enters box, pressure changes and can measure new

volume in box.

• Very high correlation with underwater weighing.

• Easier than underwater weighing for people uncomfortable in

water.

SKINFOLD TECHNIQUE

• 1. Triceps: Vertical fold at the posterior midline of the upper arm, halfway between the tip of the shoulder and tip of the elbow; elbow remains in an extended, relaxed position

• 2. Subscapular: Oblique fold just below the bottom tip of the scapula

• 3. Suprailiac (iliac crest): Slightly oblique fold just above the hip bone (crest of ileum); the fold follows the natural diagonal line

• 4. Abdomen: Vertical fold 1 inch to the right of the umbilicus

• 5. Thigh: Vertical fold at the midline of the thigh, two-thirds of the distance from the middle of the patella (knee cap) to the hip

• Two other sites include:

• Chest (males): Diagonal fold (with its long axis directed toward the nipple) on the anterior axillary fold as high as possible

• Biceps: Vertical fold at the posterior midline of the upper arm

JACKSON-POLLOCK 3-SITE SKINFOLD EQUATIONS

GIRTH MEASUREMENTS

• The following five-step example shows how to compute percentage fat, fat mass, and FFM for a 21-year-old man who weighs 79.1 kg:

• Step 1. Measure the upper arm, abdomen, and right forearm girths with a cloth tape to the nearest 0.25 in (0.6 cm): Upper arm =11.5 in (29.21 cm); abdomen =31.0 in (78.74 cm); right forearm =10.75 in (27.30 cm).

• Step 2. Determine the three constants A, B, and C corresponding to the three girths, Constant A corresponding to 11.5 in =42.56; constant B corresponding to 31.0 in = 40.68; and constant C corresponding to 10.75 in = 58.37.

• Step 3. Compute percentage body fat by substituting the appropriate constants in the formula for young men

Girth Measurement: Conversion Constants to Calculate Body Density for Women

BIOELECTRICAL IMPEDANCE ANALYSIS

• BIA measures impedance by body tissues to the flow of a small

(<1mA) alternating electrical current (50kHz)

• Impedance is a function of:

• electrical resistance of tissue

• electrical capacitance (storage) of tissue (reactance)

BIA: BASIC THEORY

• The body can be considered to be a series of cylinders.

• Resistance is proportional to the length of the cylinder

• Resistance is inversely proportional to the cross-sectional area

• Volume is equal to length of the cylinder times its area

• Therefore, knowing the resistance and the length, one can calculate volume.

• Assuming that the current flows thru the path of least resistance (water) , then the volume determined is that of body water.

BIA ASSESSMENT GUIDELINES

• No diuretic medications with a week of test

• Avoid alcohol within 2 days of test

• Avoid exercise within 12 hours of test

• Avoid eating or drinking within 4 hours of test

• Urinate within 30 minutes of test

• Assume fat free mass has a constant proportion of water (about

73%)

• Then calculate fat free mass from body water

• Assume BW = FFM + FM

• Then calculate fat mass and %body fat

• %fat = 4.57 ÷ (1.1411 - ((BW * Resistance) ÷ Ht2)) - 4.142 * 100

ht = length of the conductor

Males

FFM = -10.68 + 0.65H2/R + 0.26W + 0.02R

Females

FFM = -9.53 + 0.69H2/R + 0.17W + 0.02R

Where

FFM = fat free mass (kg)

H = height (cm)

W = body weight (kg)

R – resistance (ohms)

% BF = 100 x (BW-FFM)/BW

DATA

R = 520 ohms

BW = 170 lbs = 77.3 kg

H = 70” = 178 cm

CALCULATIONS

FFM = -10.68+(0.65H2/R)+0.26W+0.02R

FFM = -10.68+(0.65x1782/520)+0.26(77.3)+0.02(520)

FFM = -10.6 + 39.6 + 20.1 + 10.4 = 59.5 kg

FM = W – FFM = 77.3 – 59.5 = 17.8 kg

%BF = (17.8/77.3)x100 = 23%

DUAL-ENERGY X-RAY ABSORPTIOMETRY

DUAL-ENERGY X-RAY ABSORPTIOMETRY

• Two different energy level X-rays

• Lean, fat, and bone mass each reduce (attenuate) the X-ray signal in unique ways

• Computer analyzes scan point by point to determine body composition

Method

• Low dose radiation

• 20-30 minutes

• Applicable to young and old

HEIGHT - WEIGHT TABLES• Body composition is a better indicator of fitness than

body weight/height. Being overfat (not necessarily overweight) has a negative impact on exercise/athletic performance. Standard height-weight tables do not provide accurate estimates of what you should weigh because they do not take into account the composition of the weight. A subject can be overweight according to these tables yet have very little body fat.

WAIST TO HIP RATIO• Made with a tape measure

• Waist - at the narrowest part of the waist between the umbilicus and xiphoid process

• Hips - biggest part of the gluteals

• Divide the hip measurement into the waist measurement to obtain the WHR

• Risks increase with increasing ratios

• very high risk >0.94 young men and 0.82 young women

• very high risk >1.03 older (60-69 years) men and 0.90 for older women

BODY MASS INDEX (BMI)

• Ratio of a person’s weight (kg) to the height squared (m2)

• Used to categorize people with respect to their degree of obesity

• Not used to determine % fat

• 20-25 kg/m2 - desirable

• 25-29.9 kg/m2 - overweight

• >30.0 - obesity

NEAR INFRARED INTERACTANCE

• Based on the premise that the degree of infrared light absorption

is related to the composition of the substance through which light

passes

• Fat and Fat-Free Mass absorb and reflect light differently

• Emit infrared light at wavelengths of 940-950 nm into a body part

(ie., biceps) and measures the intensity of the re-emitted light

• More specific equations/machines are necessary, researchers

does not support NIR as a valid method to assess human body

composition.

ULTRASOUND• Based on reflection of sound

• Fat content increases the time is required for sound to reflect off of bone and muscle.

• Ultrasound exhibits high reliability for repeat measurements and subcutaneous fat thickness at multiple sites in the lying and standing positions on the same day and different days.

• It shows validity for assessing FFM of high school wrestlers which may prove useful as a field based body composition assessment method.

IMAGING TECHNIQUES

• Based on imaging of body tissues

• Based on cross sectional area measures calculated at different

levels of the body.

• Very precise measure of body composition

• Expensive and not practical measure for most uses

OBESITY

DEFINITIONS

• Overweight: Body mass index (BMI) 25 - 29.9 kg.m-2

• Obese: BMI > 30 kg.m-2

• Percent Body Fat: Proportion of total weight that is fat.

TYPES OF OBESITY

Android Obesity – central or upper body adiposity (apple-shaped).

Increased WHR indicative of android obesity

Android obesity = higher risk of heart attack

Gynoid Obesity – excess fat deposited in hips and thighs (pear-shaped).

Gynoid obesity = lower risk of heart attack

The accumulation of visceral body fat is typical of the android (male) fat pattern

males: visceral accounts for 10-35% of total fat

females: visceral accounts for 8-13%of total fat

WORLD HEALTH ORGANIZATION CRITERIA FOR OVERWEIGHT AND OBESITY BY BMI

• Category BMI

• Underweight < 18.5

• Normal Weight 18.5 – 24.9

• Overweight 25.0 – 29.9

• Obese Class I 30.0 – 34.9

• Obese Class II 35.0 – 39.9

• Obese Class III > 40

DETERMINING BODY FRAME SIZE AND STRATURE

• Body frame size becomes a useful measure for evaluating normalcy of body weight with standardized charts that categorize weight by frae size.

• A combination of stature and bony widths adequately defines BFS, because BFS relates to the fat free body mass and not body fat.

• MEASUREMENTS

• Stature(height [HT]) measured in cm

• Biacromial diameter (cm) measured as the distance between the most lateral projections of the acromial processes.

• Bitrochanteric diameter(cm) measured as the distance between the most lateral projection of the greater trochanters.

DETERMINING BODY FRAME SIZE AND STRATURE

• CALCULATIONS

FEMALE : BFS x Ht + 10.375 + (∑Bia + Bitroc)

MALE : BFS x Ht + 8.239 + (∑Bia + Bitroc)

BFS MALE= Ht ×8.239+ ∑Bia + Bitroc

BFS FEMALE= Ht ×10.357+ ∑Bia + Bitroc

Regression analyses determine BFS values for women and men from Ht and sum of the biacromial and bitrochanteric bone diameters (∑ Bia + Bitroc).

(∑ Bia + Bitroc) – sum the average biacromial and bitrochanteric diameter measurement

FRAME SIZE CATEGORY

THANK YOU