Contents Levels of Body composition Methodology for assessing

Περιεχόμενα ενότητας - Contents • Levels of Body composition • Methodology for assessing body composition – Invasive – Non invasive – Direct assessment – Indirect assessment • Conclusions 5

Body Composition Research There are three interconnecting areas: 1. body-composition levels and their organizational rules 2. measurement techniques 3. biological factors that influence body composition 6

Levels of Body Composition 7

Measurement Techniques 1. Total body water (TBW) as measured by double labeled water and Extracellular Water (ECW) as measured by Sodium Bromide (Na. Br) 2. Total body potassium (TBK) by whole-body 40 K counting 3. Body volume by underwater weighing (UWW) 4. Total body fat, Bone density and Lean body mass by dual-energy Xray absorptiometry (DXA or DEXA) 5. Air Displacement Plethysmography for body composition 6. Skinfolds/circumferences by anthropometry (Anth) 7. Body resistance by single or multi-frequency bioelectrical impedance analysis (BIA) 8. MRI and CT for body composition 9. MRS for metabolites and fat infiltration 8

1. Total body water – Συνολική Ποσότητα Νερού (TBW) Body Composition (fat free mass and fat mass) can be calculated from body mass (weight) and TBW with an assumption that Fat-Free Mass (skeletal muscle) contains all the body water which comprises 730 gr/Kg fat free mass Pros: • This technique can be performed in any place • Accuracy & repeatability are very high • No side effects Cons: • The cost and the technical difficulties associated with isotope analyses and • The requirement for an isotope ratio mass spectrometer (φασματογράφο μάζας) and sample preparation systems often limit the use of this method 9

Protocol - Total body water (TBW) • Double Labeled Water 2 H 2 O (Διπλά Συμασμένο Νερό) • The procedure begins with a bolus administration of labeled water (diluted in 1 -2 liters of tap water). • Within two to three hours, the double water equilibrates with body water and provides a measure of the volume of the TBW pool. • The labeled water is then excreted from the body through all routes of water loss. Samples from • Blood, saliva or urine (24 -hour urine collection) • The amount of water NOT excreted is called Intracellular and the amount of water excreted is called extracellular 10

1. 2 Extracellular water – Εξωκυτταρικό Νερό (ECW) with Sodium Bromide (Na. Br) Extracellular water is physiologically important because it provides: 1. Environment for oxygen and nutrients transport 2. A route for clearance of cell metabolism Why is important to know the amount of ECW? 1. Calculate the “Intracellular water” (ICW) from Total Body Water 2. Assess the level of edema 11

Extracellular water (ECW) with Sodium Bromide (Na. Br) Why Bromide ? – Distributed in the extracellular space – Advantage of good absorption – Slow excretion – Low membrane penetration • Na. Br is distributed in the human body by intravenous injections • Within two hours Bromide penetrates Red Blood Cells • ECW can be calculated from the increase in Bromide concentration between baseline and post-dose blood samples. • The amount of Na. Br remains in the blood serum represents the ECW 12

2. Total body potassium (Συνολική Ποσότητα Καλίου) (TBK) • Whole-body (40)K counting is a valuable tool for assessing cellular changes in body composition • A fairly new approach to assess body composition as body cell mass (BCM) (Συνολική Κυτταρική Μάζα) • BCM is defined as the total mass of ‘oxygen-exchanging, potassium-rich, glucose-oxidizing, work-performing’ cells of the body…which is… 13

Total body potassium (TBK) • BCM is considered the actively metabolizing portion of the body, which is known as MUSCLE • Potassium is almost exclusively in intracellular space (95%) found chiefly in muscle (hence, essentially not found in fat, bone or extracellular water) • Total body potassium (TBK) concentration is linearly correlated with the size of the BCM • An accurate measure of BCM would prove extremely useful for establishing an individual’s state of health or disease over time, possibly assisting to the prevention of sarcopenia 14

3. Body volume – Under Water Weighting – Υποβρύχια Ζύγιση (UWW) • Used to be the “Gold Standard” for measuring body composition • A technician submerges a person underwater • The person exhales fully while underwater • The technician measures the person’s weight under water 15

Body volume – Σωματικό Όγκος Example: Dry weight = 93 Kg, Underwater weight 6. 5 Kg 1. Dbody = body mass / body volume So…. . volume body = 93 – 6. 5 = 86. 5 Dbody= body density, Liters Density body = 93 / 86. 5 = 1. 075 g ml-1 body mass= weight, % Body Fat = (495/1. 075)-450= 10. 5% Fat weight = 93*(10. 5/100)= 9. 7 Kg body volume = weight – underwater Fat Free Mass = 93 – 9. 7 = 83. 3 Kg weight % Body Fat calculation 2. % Body Fat = (495 / Dbody)-450 (Siri equation) 16

Body volume – Under Water Weighting This equations assumes that • Fat mass density is constant at different sites (0. 007 g cm-3) which is correct • Fat free mass is constant throughout the body (1. 100 g cm-3) which is more problematic • Bones always represents the 17% of the fat free mass • Under the best circumstances, underwater weighting can estimate body fat within 2 – 3% margin of error e. g. meaning that if your UWW test shows a 20% fat, this value could be no lower than 17% nor higher than 23% 17

Body volume – Under Water Weighting Pros : • Fairly accurate • Inexpensive Cons : • Time and labor intensive • Often disliked by obese subjects • Discomfort about being tested in the water tank • Inability to perform maneuvers • Required pool or water tank 18

4. Total body fat, Bone density and Lean body mass by DEXA • Dual Energy X-ray Absorptiometry (DEXA) (μέθοδο της απορρόφησης διπλής ενέργειας δέσμης φωτονίων υψηλής ενέργειας ) 19

% Body Fat, Bone Density and Lean Body Mass by DEXA • Used as “Reference Technique” for whole body composition • Estimates • % body fat • lean body mass (LBM) • bone density • With compartmental analysis we can get information for parts of the body (ex. Left arm, right leg, trunk fat etc) 20

DEXA methodology • The concept of DEXA is that: – Photon attenuation (εξασθένηση) in vivo is a function of tissue composition – The body is scanned with two different energies at the supine position, pixel by pixel – The ratio of the energy attenuation is calculated (R value) – DEXA systems assumes that the body consists of three components (fat, bone mineral, lean-soft tissue) that are distinguishable by X-ray attenuation 21

Total body fat, Bone density and Lean body mass (DEXA) Pros: • • High accuracy Whole body measurements Compartmental analysis Low cost (per measurement) Cons: • X-ray emission (1/10 th of chest X-ray) • Limitation in very obese patients (weight limit 150 Kg) • Differences at values between different DEXA companies (Hologic vs GE-Lunar) 22

5. Air Displacement Plethysmography (BOD POD) (πληθυσμογράφος αέρα) • Plethysmography refers to the measurement of size, usually volume (όγκος) • In air-displacement plethysmography, the volume of an object is measured indirectly by measuring the volume of air it displaces inside an enclosed chamber (plethysmograph). 23

Air Displacement Plethysmography (BOD POD) • Air-displacement Plethysmography offers several advantages over established reference methods, including a quick, comfortable, automated, noninvasive, and safe measurement process • Accommodation of various subject types (eg, children, obese, elderly, and disabled persons) • It is still expensive • Accuracy is high only when it used multi dimensional measurements (more than one technique at the same time) 24

Air Displacement Plethysmography (BOD POD) • Human body volume is measured when a subject sits inside the chamber and displaces a volume of air equal to his or her body volume. • Body volume is calculated indirectly by subtracting the volume of air remaining inside the chamber when the subject is inside, from the volume of air in the chamber when it is empty. • The BOD-POD system includes the BOD POD plethysmograph, electronic weighing scale, calibration weights and cylinder, computer, and software. 25

6. Skinfolds (Δερματοπτυχές) / Circumferences (Περιφέρειες) • • Anthropometrical assessments Weight & Height (bare foot and light clothing) Skinfolds (1/2 of body fat is located as subcutaneous fat): Biceps, Triceps, Chest, Abdomen, Thigh, Calf, suprailium etc. Circumferences & Diameters Waist to hip ratio (WHR) Metabolic Index (MI) 26

Skinfolds • Calculation of Body Density from Skinfolds • Males: Body Density = 1. 1093800 – 0. 000826(x 2) + 0. 0000016(x 2)20. 0002574(x 3) • x 2= sum of chest, abdomen & thigh skinfolds (mm) • x 3= age in years • Females: Body Density = 1. 0994921 -0. 0009929(x 4) + 0. 0000023(x 4)20. 0001392(x 3) • x 3= age in years • x 4= sum of triceps, suprailium & thigh skinfolds (mm) • Calculation of % Body Fat • %BF = (457/Body Density) – 414. 2 27

Circumferences • Waist to hip ratio (Περιφέρεια Μέσης / Πυέλου) • Waist circumference measured at the level of umbilicus and hip circumference measured as the maximal circumference at the level of the buttocks • Difficulties to identify a waist line is severe obesity • Needs two trained personnel (one to spot the tape measure) • Metabolic Index = (body weight x waist area)/(body height 2 x hip area) 28

Skinfolds /circumferences Pros: – – Correlates fairly with UWW Inexpensive Field test Suitable for massive test Cons: – – Experienced and skilled personnel Large error if perform incorrectly Difficult to perform in obese subjects More than 400 equation developed for different populations 29

Body Mass Index (BMI or Quetelet’s index (Δείκτης Μάζας Σώματος) • BMI represents the ratio of a person’s body weight to the square of his or height • BMI = weight (kg) / height (m)2 • Example: 75 kg/(1. 75 m*1. 75 m) = 24. 5 • Provides important clue to your overall health • BMI above 30 is correlated with type 2 diabetes, high blood pressure and heart diseases • BMI ranges from: 19 Low Weight (λιποβαρή), 19 -24 Normal (φυσιολογικό), 25 -29 Overweight (υπέρβαρο), 29 -35 Obese (παχύσαρκο), >35 Morbid Obese (παθολογικά παχύσαρκο ή νοσηρή παχυσαρκία) 30

BMI can not distinguish between different types of body shape 31

BMI can not distinguish between different types of body shape 32

Body Mass Index (BMI or Quetelet’s index ) • BMI can not distinguish between different shapes of fatness 33

7. Body resistance – Bioelectrical Impedance Analysis (BIA) (Αναλυτής Βιοηλεκτρικής Αγωγιμότητας) Waters and electrolytes permit the flow of an electrical current and BIA utilizes this simple principle to measure body water compartments and resistance! 34

Body resistance – Bioelectrical Impedance Analysis (BIA) • Single (1 -50 k. Hz) frequency • Multi (1 -50 & 200 -500 k. Hz) frequency 35

Body resistance – Bioelectrical Impedance Analysis (BIA) • BIA measures the body impedance (αγωγιμότητα) using electrodes that are connected from one leg to the other leg or to the arm to form a circuit for the current to pass through • BIA “predicts” total body water (TBW) and fat free mass (FFM) • BIA estimations are based on the assumption that: • The total body behaves as a cylindrical conductor with uniform cross-sectional area • Human body has a homogenous composition with a specific resistance that is constant thought out the body 36

Body resistance – Bioelectrical Impedance Analysis (BIA) Pros • • • Non invasive technique Portability Safety Low cost Correlates better with body fat rather than BMI Cons • Not reliable in very obese subjects • Prone to error due to water retention • Underestimates fat mass in obese subjects 37

8. Magnetic Resonance Imaging (MRI) 38

Magnetic Resonance Imaging (MRI) • Whole body analysis • % Subcutaneous Adipose Tissue (SAT) • % Visceral Adipose Tissue (VAT) • % Fat Infiltration (Λιπώδεις Διήθηση) • % Skeletal Muscle 39

MRI: Subcutaneous: Visceral Subcutaneous - υποδόριο λίπος (SAT) MRI slice L 4 -L 5 Visceral - ενδοκοιλιακό λίπος (VAT) 40

Central Obesity 41

Thigh Musculature vastus medialis rectus femoris sartorius vastus lateralis long adductor gracilis vastus intermedius great adductor semimembranosus biceps femoris semitendinosus 42

Magnetic Resonance Imaging (MRI) Pros: • Very safe (no X-ray use) • Very reliable • Separation between VAT and SAT Cons: • • • Very expensive Limited to patients without metal implants Claustrophobia Labor analysis and trained staff Limitation to waist size 43

8. 2 Computer Tomography (CT) 44

Computer Tomography (CT) • Very similar to what we can measure with MRI • Different technology but similar results • Different representation of the tissue (fat is dark, muscle is gray, bones are white) 45

Computer Tomography (CT) Pros: • Comparable results with the MRI • Cheaper than MRI Bone Muscle • No problem with metal implants Fat Cons: • X-ray (high values) CTimageanalysisfor CT quantifyingmusclearea quantifying andmusclecomposition. and 46

9. Magnetic Resonance Spectroscopy (MRS) Allows for more muscle information: 1. Intramyocellular lipids & extramyocellular lipids 2. Various amino acids & other biochemicals (carnosine, creatine, choline, lactate, etc. ) -metabolite peaks btwn water & lipid peaks Requires additional acquisitions 1. Time (subject & researcher) 2. Expense (magnet & additional coil) 47

Magnetic Resonance Spectroscopy (MRS) unsuppressed 48

Tissue sample size Voxel Size Muscle Biopsy 49

Summary • The evaluation of body composition is a very important task and needs skilled personnel • There are many ways for assessing body composition, however the selection of the appropriate approach is related to the studied population and the level of accuracy. 50