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Mesurment of body composition
- 1. Presentation on : Measurement of body composition
- 2. Assessing Body Composition The different types of methods used in the determination of body composition may be discussed under the following •Chemical analysis of whole body •Physical measurement or nutritional anthropometry •Advance methods The search for valid methods of measuring body composition that are practical and inexpensive is an ongoing process for exercise scientists and nutritionists.
- 3. •Total body potassium using 40k: Potassium in intracellular fluid index for fat free mass in healthy subjects assuming that free mass has a constant amount of k. A constant fraction (0.02gama)of k in body as isotope 40k- units gama rays or 1.46mev. allowing (measures radiation) by spectrometer. •The measurement of k in body •Calculation of total body k(gms) from 40k •Conversion of total body k to mmol k Mmol k= total body k (gms)/atomic count of k (39.098) •Calculation of fat free mass (kg) from TB k assuming average fat free mass = 69.4mmol/kg •Calculation of TB F (kg)= body weight. (kg) – ffm (kg) •Calculation of % body fat =TBf/body weight * 100
- 4. Body composition from conductivity Another method is bioelectrical impedance analysis (BIA), which uses the resistance of electrical flow through the body to estimate body fat. Unfortunately, BIA is highly sensitive to hydration status and water intake. Drinking water dilutes the electrolytes in the body making it less conductive as does increasing body fat.
- 5. It is based on change in electrical conductivity when subject is placed in an electromagnetic field. Fat free mass is composed of electrolyte- containing H2O & fat is a poor conductor. 1.Subject lies supine in a long coil to 5MHz current is passed for few seconds inducing a magnetic . 2. measurement is taken when it is empty. And the difference re present the measurement
- 6. Isotope dilution (hygrometry) Deuterium dilution can be used to measure total body water TBW, allowing estimation of FFM. A dose of water labelled with deuterium is given and, following equilibration, enrichment of the body water pool measured using samples of either saliva, urine, or blood. Samples are generally analysed by isotope ratio mass spectrometry; however, clinical services could be based on a substantially cheaper but more labour intensive spectrophotometric technique.
- 7. Other body fluid compartments using isotope dilution Estimate the volume of various body fluid compartments, to in turn can be used to derive estimates of the two components of fat free mass (ffm) , extracellular mass(ECM) and body cellular mass(BCM). A dilution technique involving the intravenon injection of 22Na & titrated H2O- to measure ECM and BF. BCM is derived from total exchangeable potassium to in turn determine Ke(kg)=TBW(kg)* R- Na e (kg) R= sum of Na & K content of sample of whole blood , divided by its water content (R is a dimensionless constant less than quantity) and Na e = exchangeable sodium (kg) Ke is not directly determined from 42k because of short life span of this isotop. BCM is estimated by Moore et al (1963) BCM (kg)= 8.33* Ke Na e measures fluid not mass There fore, ECM(kg)= FFM(kg)- BCM(kg) There fore, body fat = body weight – FFM (kg)
- 8. Total body nitrogen Measures body protein mass of nitrogen bears a fixed ratio to mass of protein (1g N= 6.25g protein) patients are laid down in sup rive portion then bomb are lid the patient with cyclotron or neutron generator. Units X-rays at 10.83Mq n- are counted by Na I sodium Iodide detectors from the whole body. the detected gama –rays counts are proportional to the absolute mass of total body N2.
- 9. Dual energy x ray absorptiometry Dual energy x ray absorptiometry (DEXA) was developed to measure bone mineral mass, which is calculated from the differential absorption of x rays of two different energies. The body is scanned by 2-x ray beams of high densities & undisclosed computer programs can be used to estimate bone minerals, soft tissues , mineral content and density of pelvic region. It have difficulty in estimating visceral fat and soft tissues of head. DXA is quick and acceptable for children down to about 4 years, and can also be used in small infants.
- 10. Physical measurement or nutritional anthropometry Skinfold Method Skin fold technicians can be trained rather easily, but must practice on at least 50-100 clients before the skin fold technique is mastered The skinfold method of measuring body fat is a practical, economical, and administratively feasible field technique for body composition analysis. It involves measuring the skinfold (subcutaneous fat) thickness at specific sites of the body. Most equations use the sum of at least three skinfolds to estimate body density from which body fat may be calculated.
- 11. This is done using a tool called a calliper •Take measurements on the right side of the body. •Mark client up. •Pinch skin (KM) above mark •Pull fat away from muscles •Place caliper halfway between top and bottom of mark •Allow caliper to settle (1–2 seconds) •Take reading — repeat 15 seconds •Add up total (4) — average Calculate body fat %
- 12. Body composition from body density The most accurate estimation of body composition is derived from body density by means of the equation of fractional densities which states that the overall density of a mixture containing more than one substance (each with a different density) can be calculated if the proportion and density of each component substance is known. For determination of body composition the body is often assumed to be composed of 4 basic substances ("four compartment model") with the general form of the equation as follows. 1/Db = w/Dw + f/Df + p/Dp + m/Dm Where: Db = overall body density, w = proportion of water, f = proportion of fat, p = proportion of protein, m = proportion of mineral, Dw = density of water, Df = density of fat, Dp = density of protein, Dm = density of mineral.
- 13. In a research laboratory setting the overall density of the body (Db) is calculated from its mass and volume (Db = mass/volume). The mass of the body is found by simply weighing a person on a scale. The volume of the body is most easily and accurately determined by completely immersing a person in water and calculating the volume of water from the weight of water that is displaced (via "underwater weighing").
- 14. Body composition measurement with Whole-Body Air Displacement Plethysmography (ADP) technology Another technique for measuring body composition has been developed for measuring body volume using a different method than underwater weighing. The technique uses air, as opposed to water and is known as Whole-Body Air Displacement Plethysmography (ADP). Subjects enter a sealed chamber that measures their body volume through the displacement of air in the chamber. Body volume is combined with body weight (mass) in order to determine body density. The technique then estimates the percentage of body fat and lean body mass (LBM) through empirically derived equations similar to those used with underwater weighing (for the density of fat and fat free mass).
- 15. Magnetic resonance imaging MRI is an imaging technique that estimates the volume rather than the mass of adipose tissue. By analysing the absorption and emission of energy in the radio frequency range of the electromagnetic spectrum, the technique produces images based on spatial variations in the phase and frequency of the energy absorbed and emitted. It primarily addresses hydrogen nuclei, located either in water or fat, and uses these data to discern tissue types in “imaging slices” which can then be summed to calculate regional tissue volumes. Advance methods
- 16. The main advantage of MRI over other techniques is its capacity for estimation of regional body composition, and it is currently the only accurate and viable approach for the estimation of intra‐abdominal adipose tissue. However, recent studies support the use of waist circumference as a robust index of abdominal fat, and a useful index of visceral fat.
- 17. Body composition from total body imaging Computerized tomography (CT) scan based on the relationship between the degree of attention of an X- ray beam & density of the tissues through the beam has passed. Patients are laid in supine position in scanner gantry , then X- ray beam is passed undergo alteration, the intensity of patient is recorded and stored in the scanner computer. It is used to asses change in visceral organs mass in underweight and obesity. And not used for pregnant women and children.
- 18. Body composition from ultrasound Ultrasound has also been used to measure subcutaneous fat thickness, and by using multiple points an estimation of body composition can be made. A high frequency sound waves are emitted from ultra sound meter which penetrate the skin and pass through the adipose tissue and they reach muscle tissue. At adipose tissue it interfaces some waves and are reflected back to meter and noted. Ultrasound has the advantage of being able to also directly measure muscle thickness and quantify intramuscular fat .
- 19. Bioelectrical Impedance Analysis Total body water constitutes the largest component (72%) of fat-free body weight. Bioelectrical impedance analysis (BIA) is based on the fact that the body contains intracellular and extracellular fluids capable of electrical conduction.
- 20. It measures the impedance of a weak electric current passed between right ankle to right wrist of the hand. Impedance is proportional to square of the length of the conductor/ subject divide by its volume. Two electrodes are placed on wrist and ankle and a thin layer of gel is applied to skin. The lowest resistance value is calculated and used to calculate conductivity and hence it predicts fat free mass.
- 21. Chemical method • Total body potassium using 40k • Body composition from conductivity • Isotope dilution (hygrometry) • Total body nitrogen • Dual energy x ray absorptiometry Physical method • Skinfold Method • Body composition from body density • Body composition measurement with Whole-Body Air Displacement Plethysmography (ADP) technology Advance method • Magnetic resonance imaging • Body composition from total body imaging • Body composition from ultrasound • Bioelectrical Impedance Analysis
- 22. Name of methods Total body potassium using 40k Body composition from conductivity Isotope dilution (hygrometry) Total body nitrogen Dual energy x ray absorptiometr y How to measure By usinfg 40k isotope By electrical flow Deuterium dilution 1g of nitrogen = 6.25g of protien body is scanned by 2-x ray beams of high densities From what to measure By measuring total potassium in body Electrolytes composition Fluid of body Na 1 sodium iodide absorption of x rays of two different energies What is determined Total body fat Fat free mass Fat free mass Totle body N2 bone mineral mass
- 23. Name of methods Skinfold Method Body composition from body density Body composition measurement with Whole-Body Air Displacement Plethysmography (ADP ) technology How to measure Use of caliper 1/Db = w/Dw + f/Df + p/Dp + m/Dm Db = mass/volume In air chamber From what to measure Folding skin Density of=water,protien,fa t,minral Water displacement Air displacement What is determined body fat Density of body Density of body Body density
- 24. Name of methods Magnetic resonance imaging Body composition from total body imaging Body composition from ultrasound Bioelectrical Impedance Analysis How to measure By analysing the absorption and emission of energy in the radio frequency range of the electromagnetic spectrum X- ray beam high frequency sound waves weak electric current passed between right ankle to right wrist of the hand From what to measure MRI machine C.T. Scan machine Ultrasound machine Bioelectrical impedance analysis What is determined regional body composition It is used to asses change in visceral organs mass in underweight and obesity fat thickness fat free mass