CHAPTER 18 LESSON 4: MONITORING BODY COMPOSITION
Body Mass Index Categories If yet another body compartment is considered, a 4-compartment model can be produced. This model separates body weight into fat mass, water, bone, and residual. These models are often viewed as a true gold-standard estimation of body composition. In order to obtain a 4-compartment model, measurements...
... of body weight, body volume, water, and bone content are needed. Each of these items can be obtained by some of the individual techniques described next.
Body Mass Index Categories Underwater Weighing When the individual's body weight is divided by their body's volume, the body density can be found. This is then used to ...
....predict body composition using prediction equations, as in skinfold measurement, using a 2-compartment model.
Body Mass Index Categories In addition to the fat compartment, these models typically include water and residual (a term referring to everything else in the body). In order to produce a 3-compartment model, it is typically necessary to conduct ..
...multiple assessments on an individual and mathematically combine the results.
Body Mass Index Categories Ultrasound ultrasound has the ability to actually see where the fat layer is located. Ultrasound assessments of fat thickness can be performed at the same sites as a skinfold assessment and ...
...prediction equations can be used to estimate the overall body composition using a 2-compartment model. the fat-thickness measurement at particular sites can be used to determine if a client is gaining or losing fat at these locations.
Body Mass Index Categories Skinfolds The density of the body obtained from these equations is used to predict the body fat of an individual using a 2-compartment model. measuring the thickness of the fat layer at specific locations can be used to get a general idea of whether body-fat loss is occurring at a particular location. Although the skinfold method has the advantage of being portable and cheap,...
...the experience and skill of the health professional performing the assessments can greatly impact the accuracy of body-composition estimates.
Body Mass Index Categories Getting Technical Although you will probably not assess your clients using a 4-compartment model, this gold-standard method is often used to determine the accuracy of more common assessment methods. To build a 4-compartment model, measurements of body weight, body volume, water, and bone content are needed. Body volume can be obtained by ...
...underwater weighing or air displacement plethysmography (ADP); water can be estimated by bioelectrical impedance analysis (BIA) and bone can be estimated using dual-energy X-ray absorptiometry (DXA).
Methods of Assessing Body Composition DEFINITION Any method of body-composition assessment that divides the body into two major parts - typically, these parts are fat mass and fat-free mass. Most common methods of body-composition assessment use a 2-compartment model
2-Compartment Model
DEFINITION A method of body composition assessment that divides the body into three major parts - typically, these parts are fat mass, water, and everything else (i.e., the residual).
3-Compartment Model
Body Mass Index Categories DEFINITION A method of body composition assessment that divides the body into four major parts - typically, these parts are fat mass, water, bone, and everything else (i.e., the residual). These models are viewed as a gold-standard method of body-composition assessment....
4-Compartment Model
Body Mass Index Categories Bioelectrical Impedance Analysis (BIA) DEFINITION A technology that estimates body composition based on the fluid content - by determining how easily small electrical currents travel through the body, BIA can predict the amount of lean tissue (higher water content and easier flow of electricity) and fat tissue (lower water content and more resistance to electrical currents).
Bioelectrical Impedance Analysis (BIA)
Q Some clients may not want to have their fat pinched when assessing their body fat percentages using the skinfold method. What would be the best alternative method used while keeping practicality and cost in mind?
Bioelectrical Impedance Analysis (BIA)
Body Mass Index Categories Skinfolds DEFINITION The estimated thickness of fat under the skin at specific locations when entered into an equation.
Body Density
Methods of Assessing Body Composition DEFINITION An individual's weight divided by their height squared, typically shown in units of kilograms/meters².
Body Mass Index (BMI)
Body Mass Index Categories Circumferences DEFINITION Measurements of the circumferences of different body parts - these measurements provide some basic indication about the distribution of fat in the body, although they cannot actually distinguish between muscle and fat.
Circumference Measurements
Body Mass Index Categories Other Methods DEFINITION Imaging procedure to create scans and pictures of inside the body.
Computed Tomography (CT)
Body Mass Index Categories Other Methods
Computed tomography (CT) Magnetic resonance imaging (MRI) Hydrometry Near-infrared interactance (NIR)
Q 2 COMPARTMENT-MODEL
Correct! Often separates fat mass, and fat mass free and are most common
Body Mass Index Categories DEFINITION A body composition assessment method that measures whole-body and regional (arms, legs, and trunk) body composition using low-energy X-rays.
Dual-Energy X-Ray Absorptiometry (DXA)
Q When comparing different body composition assessment methods, it is important to weigh the cost and practicality of each methods, in addition to accuracy. However, if cost and practicality was not a factor, which method would provide the client the most accurate body composition results?
Dual-energy x-ray absorptiometry
Body Mass Index Categories Other Methods DEFINITION The process of monitoring water within the body to determine body composition
Hydrometry
QB 3-COMPARTMENT MODEL
Includes fat, water and "residual" compartments
Body Mass Index Categories Other Methods DEFINITION A medical imaging process that measures the reaction of tissue nuclei to magnetic fields to produce images of inside the body.
Magnetic Resonance Imaging (MRI)
Monitoring Body Composition DEFINITION The makeup of an individual's body - major components of interest include fat mass and fat-free mass (i.e., water, bone, protein, etc.).
Monitoring Body Composition
Body Mass Index Categories Other Methods DEFINITION A technique using a specialized probe against the body, emitting infrared light to estimate body composition of an individual.
Near-Infrared Interactance (NIR)
Q 4 COMPARTMENT MODEL
Separates body weight into fat mass, water, bone, and residual
Body Mass Index Categories DEFINITION A body composition estimation method that is based on measuring the thickness of the fat layer under the skin - using calipers, the skin and fat are pinched at certain locations on the body to determine their thickness. These measurements are placed into a series of equations, which provide an estimate of body-fat percentage.
Skinfolds
Body Mass Index Categories Ultrasound DEFINITION Uses high-frequency sound waves emitted by a probe to visualize different parts of the body
Ultrasound Technology
Body Mass Index Categories Underwater Weighing DEFINITION A body composition assessment method that involves the estimation of the 3-dimensional volume of the body through measurement of an individual's body weight while they are completely submerged under water
Underwater Weighing (Hydrodensitometry)
Body Mass Index Categories BMI (kg/m2) Weight Category 30.0-34.9
Weight Category/ Obesity class I
Body Mass Index Categories BMI (kg/m2) Weight Category 35.-39.9
Weight Category/ Obesity class II
Body Mass Index Categories BMI (kg/m2) Weight Category Above 40
Weight Category/ Obesity class III
Body Mass Index Categories BMI (kg/m2) Weight Category 25.0-29.9
Weight Category/ Pre-obesity
Body Mass Index Categories BMI (kg/m2) Weight Category Below 18.5
Weight Category/ Underweight
Body Mass Index Categories BMI (kg/m2) Weight Category 18.5-24.9
Weight Category/ ]Normal weight
Body Mass Index Categories Bioelectrical Impedance Analysis (BIA) is a technology that estimates body composition by calculating the fluid content of an individual's body using small currents of electricity Although specific devices vary, all have electrodes that are placed into contact with an individual's skin, typically on the hands and/or feet. Harmless current then travels through the body by some of the electrodes while others receive the signal. The BIA device automatically performs calculations to determine how easily the current travels through the body and produces ...
a 2-compartment model to split the body into fat mass and fat-free mass
Body Mass Index Categories Infrared 3-Dimensional Scanning While the use of these methods for health and fitness assessments is relatively new, several models of scanners are commercially available. In fact, several are marketed specifically to gyms and fitness facilities and it is likely that their usage will become more widespread. One potential advantage of these methods is the ability for a client to see..
a 3-dimensional avatar of their body over time in order to visualize the changes taking place. For some, this may be more meaningful than a particular body-fat percentage.
Monitoring Body Composition Body composition refers to all the separate compartments making up the human body. The composition of the body is one of several important factors to consider when evaluating an individual's health and wellness. Poor body composition has been associated with...
a number of diseases and monitoring body composition provides information about nutritional status in health and disease
Body Mass Index Categories Bioelectrical Impedance Analysis (BIA) Although BIA is most common, there are several other technologies that evaluate the body's response to electrical currents in order to estimate body composition. These include...
bioelectrical impedance spectroscopy (BIS) and electrical impedance myography (EIM). While these devices have traditionally not been commonly available to the general population, some affordable devices are now being produced and marketed to individual consumers..
Body Mass Index Categories Air Displacement Plethysmography The technique of air displacement plethysmography (ADP) exhibits similarities to underwater weighing without the necessity for a client to be submerged. Instead of the displacement of water, the displacement of air is evaluated. As in underwater weighing, this allows for ...
estimation of body volume, body density, and body composition . The primary ADP device used today is an egg-shaped chamber attached to a computer system and body-weight scale. During the assessment, the client sits inside the chamber while the device produces small changes in air pressure within the chamber. Based on the relationship between pressure and volume, the body volume of an individual is estimated.
Body Mass Index Categories Dual-Energy X-Ray Absorptiometry A major advantage of DXA is that...
it provides detailed information about the bone, lean mass, and fat in separate body regions (e.g., arms, legs, and torso). This can allow for determining the distribution of an individual's body fat, which can impact disease risk, as well as evaluating where body composition changes are occurring within the body. DXA is typically only available in medical and research settings, although some companies that provide health and wellness testing may offer DXA. Due to the substantial cost of the scanner, the charges for a DXA scan are often high.
Body Mass Index Categories Getting Technical While the 4-compartment model boasts impressive accuracy, it is typically unavailable outside of research environments. As discussed later, the most accurate techniques are ...
not always the best choice to use with your clients. Several factors, including ease of use and availability, should be considered as you think about how to assess the body composition of your clients.
Monitoring Body Composition improving body composition is...
one of the most common health-related goals. Aspirations of fat loss or muscle gain are frequently expressed by clients working with health-and-fitness professionals.
Body Mass Index Categories Water is the most prevalent substance in the body. A 4-compartment model is more accurate than DXA because it specifically includes water as one of its compartments whereas DXA does not assess water. If a client receives a DXA scan, caution them that although DXA is a valid method of assessment, there can be error in an individual person's results, which may be ...
partially due to the amount of water in their body. DXA may also overestimate body fat in lean, muscular individuals
Body Mass Index Categories Circumferences waist circumference is correlated with visceral fat and associated with ...
several diseases, including heart disease and diabete
Body Mass Index Categories Infrared 3-Dimensional Scanning Using infrared light sensors, a 3-dimensional model of an individual's body can be produced. This model can be used to automatically determine ...
the circumferences and volumes of various body segments. This means that these methods can potentially be used in multiple ways: they can represent an automated method of obtaining circumference estimates to use in body-fat equations (as in traditional circumference methods) or the volume of the body could potentially be used to predict body composition (as in underwater weighing and air displacement plethysmography).
Body Mass Index Categories Underwater Weighing , also known as hydrodensitometry or hydrostatic weighing, is a 2-compartment method that predicts body composition based on the overall density of the body. This method involves...
the estimation of the 3-dimensional volume of the body through the measurement of an individual's body weight while they are completely submerged under water. The body volume is usually corrected for the volume of air found in the lungs during the test.
Methods of Assessing Body Composition Every available method of body composition assessment provides only an estimation of an individual's real body composition. There is no method that is available that provides the exact composition of the bod.some methods provide more accurate estimations than others. , body weight is not ...
the ideal assessment of an individual's body.
Body Mass Index Categories Ultrasound . In body-composition assessment, ultrasound can be used to determine ...
the size or quality of a muscle as well as the thickness of the fat layer under the skin. By assessing the thickness of the fat layer under the skin, ultrasound can function as a more advanced version of skinfold calipers.
Body Mass Index Categories Circumferences . Similar to the measurements of fat thickness from skinfolds or ultrasound, the individual circumference measurements may be a useful indicator of whether body-composition changes are occurring at certain locations. some potentially useful sites include ...
the waist, hips, chest, upper thigh, and upper arm.
Body Mass Index Categories Dual-Energy X-Ray Absorptiometry DXA exhibits greater accuracy and precision than many assessment methods. However, it is not perfect. Although it is often called the gold standard of body composition, it has limitations. When compared to a 4-compartment model, ...
there are errors in DXA body-composition estimates that may be related to differences in the water content of the body
Monitoring Body Composition Coach's Corner Periodically assessing body composition can help evaluate the effectiveness of nutrition and exercise interventions designed to promote these changes. Performing a baseline assessment of your clients when they first start working with you will allow you...
to track their progress and obtain an objective evaluation of whether your program is producing the desired effects. Of course, body composition is only one factor and others should be considered. These may include physical performance (strength, endurance, flexibility, etc.) or more subjective factors like confidence, energy levels, and overall well-being.
Body Mass Index Categories Dual-Energy X-Ray Absorptiometry Dual-Energy X-Ray absorptiometry (DXA) uses X-rays of two different energies to estimate several aspects of body composition ). During an assessment, the individual being evaluated lies on a DXA scanning table for less than 10 minutes while X-rays are passed through the body. The amount of radiation from a DXA scan is very low and is estimated to be about the same amount received during 3 hours of a normal life. DXA evaluates differences in the X-rays when they were administered on one side of the body and when they are received by the device on the opposite side of the body. Performing these comparisons allows DXA to produce...
two different 2-compartment model comparisons: bone vs. non-bone and non-bone lean mass vs. fat mass. Because of these two comparisons, DXA ultimately provides three body compartments (bone, fat, and non-bone lean mass) and is viewed by some as a 3-compartment model.
Methods of Assessing Body Composition Instead of a single compartment, like body weight and BMI, most common methods of body composition divide the body into two compartments: fat mass and fat-free mass. In these 2-compartment models, everything that is not fat is grouped together. This fat-free mass includes ..
water, protein, bone, glycogen stores, etc. If a method further divides fat-free mass into two compartments, it is termed a 3-compartment model because body weight is now split into three separate compartments.
