Body composition is a term that describes the relative proportions of fat, bone, and muscle mass in the human body. Anthropometry is a term that describes the measurement of the human body in terms of dimensions such as height, weight, circumferences, girths, and skinfolds. Body composition and anthropometric tests have become standard practice for coaches, athletes, and fitness professionals. Valuable information regarding percent body fat (i.e., an estimate of the proportion of fat tissue within the human body), fat distribution, lean tissue mass (i.e., the mass of all nonfat tissue such as bones, muscles, and water), and limb lengths and circumferences may be gained through body composition testing.

Body composition tests may be useful for evaluating training, diet, or athletic performance, or for reducing the risk factors associated with musculoskeletal injury. For example, a body composition test may determine that an athlete is approximately 5 pounds (2.3 kg) over his desired weight and that his percent body fat is slightly higher (~1-2%) than normal. This information can help the coach and athlete determine training and dietary strategies. The coach may recommend a small reduction in daily kilocalorie intake (or just limitations in simple sugars or dietary fats), an increase in activity level to increase daily kilocalorie expenditure, or both, to reduce body fat. The athlete may add an additional 15 minutes of low- to moderate-intensity cardiorespiratory exercise at the end of a workout two or three days per week until he attains his ideal body mass and percent fat. Frequent testing will help him monitor his progress and assess the efficacy of the strategies used to attain his target body composition level.

Body composition is one of the five major health-related components of fitness (in addition to muscular strength and endurance, flexibility, and cardiorespiratory endurance), and its assessment has many benefits to children, adolescents and teenagers, adults, and elderly people, as well as performance benefits to athletes (American College of Sports Medicine 2008). In addition, body composition affects the other health-related components of fitness—that is, body mass, lean body mass, and fat content affect muscle strength and endurance, flexibility, and cardiorespiratory endurance. In general, knowledge of one’s percent body fat serves as a starting point for comparison; people do not know how they rank compared to others of their gender and age (via classification standards) until their body composition is assessed. They can use this information as a tracking metric for subsequent weight loss, weight gain, or exercise-related training programs.

For example, body composition measurements are useful for athletes in some weight-controlled sports in which body fat levels and hydration (water content) can fall to low levels. Sports such as gymnastics, wrestling, and bodybuilding require athletes to compete at either low weight or low body fat levels. Athletes in these sports can benefit greatly from routine body composition evaluations. Body composition analysis can also benefit the athlete who is training to increase muscle mass; lean tissue mass measurements can be used to evaluate training programs and measure progress. In addition, body composition tests are very useful for determining health and wellness. An excess amount of body fat, or obesity (especially in the abdominal area), is a risk factor linked to several diseases including type 2 diabetes mellitus, hypertension, hyperlipidemia, cardiovascular disease (CVD), certain types of cancer, low back pain, and osteoarthritis (Despres and Lemieux 2006; Liuke et al. 2005; Wearing et al. 2006).

Historically, some people have attempted to assess obesity via height–weight tables. One popular method involved the use of the Metropolitan Life Insurance table from 1983. This table established an optimal weight range for men and women with small, medium, and large frames. For example, a 6-foot (183 cm) male with a large frame would be considered overweight if he weighed more than 188 pounds (85 kg). Overweight is a weight in excess of the recommended range. However, overweight does not necessarily reflect obesity, because weight alone doesn’t necessarily mean that one has a high percentage of body fat. Thus, overweight is a term more suited for sedentary populations and not athletes or those who exercise regularly. An athlete with greater lean tissue mass will also have a higher body weight; thus, height–weight tables have little value in the athletic world. Body weight itself is not a direct risk factor per se. However, an excessive amount of body fat poses major health risks. Determining percent body fat yields greater insight into health and fitness levels than body weight does.

Sport Performance and Body Composition

Sport performance hinges significantly on both health- and skill-related fitness components, including power, speed, agility, reaction time, balance, and coordination, in addition to the athlete’s mastery of sport-specific motor skills and techniques. Central to all these fitness components is body composition, which plays a crucial role in an athlete’s ability to perform at their best. An optimal level of lean body mass is fundamental for the development of strength and power, as these attributes are closely linked to muscle size. Consequently, an increase in lean body mass equips an athlete to exert more force within a given time frame, enhancing their speed, quickness, and agility by enabling more forceful ground reactions for maximal acceleration and deceleration.

Conversely, a reduction in nonessential body fat is beneficial for muscular and cardiorespiratory endurance, as well as speed and agility, since additional weight from nonessential fat increases resistance to athletic movements. This additional resistance necessitates a greater muscular force of contraction for any given workload, potentially limiting endurance, balance, coordination, and the capacity for movement. Excessive body mass and fat can also impede joint range of motion and form physical barriers to complete movement, impacting sports that demand high flexibility levels.

Athletes in various sports must maintain body composition standards specific to their discipline. Some sports favor large body stature and mass, such as American football linemen and heavyweight wrestlers, who benefit from the added inertia of greater mass. This mass, whether from lean muscle or fat, provides stability, assuming it does not compromise speed and agility. Athletes in strength and power sports—like football players, wrestlers, powerlifters, and track and field throwers—thrive with high levels of lean body mass. In contrast, endurance athletes, such as distance runners, cyclists, and triathletes, perform best with low body fat percentages. Athletes in sports requiring a high strength-to-mass or power-to-mass ratio, such as gymnasts, wrestlers, high jumpers, pole vaulters, boxers, and mixed martial artists, need to optimize strength and power while maintaining or reducing body mass to ensure competitive success. This is particularly true for athletes competing in weight classes, where maintaining a lower weight class without sacrificing strength and power can provide a competitive advantage. Sports that combine anaerobic and aerobic demands, like basketball and soccer, require athletes to maintain or increase lean body mass while keeping body fat low for optimal performance in power, speed, and endurance.

Therefore, regular body composition measurements are recommended to inform training plans that aim to reduce nonessential body fat while preserving or enhancing lean body mass. This approach supports athletes across a wide range of sports in achieving and maintaining the physical conditioning necessary for peak performance.

Practical Applications

The measurement and quantification of percent body fat are crucial for several reasons for fitness practitioners, coaches, trainers, and athletes. It allows for the identification of where athletes rank in terms of body fat (e.g., lean, average, high, obese) and can identify those at risk for conditions like obesity or eating disorders, which are of particular concern for female athletes in weight-controlled sports.

Athletes can use the data on body fat to adjust their training, diet, or both to achieve the desired body fat level for their sport. For instance, an athlete with a high level of body fat might increase the duration of aerobic exercises, intensify resistance training, or modify their diet to create a net energy deficit, aiming to reduce body fat. If an eating disorder is detected in an athlete, interventions including nutritional and psychological counseling can be initiated.

Body composition testing yields descriptive data for athletes across different sports and positions, valuable for research and for coaches to establish norms over time. This allows comparisons of athletes within a league or against program historical data to identify trends in body composition.

Moreover, body composition testing acts as a benchmark for program evaluation, enabling coaches and athletes to assess the effectiveness of training programs by measuring changes in body fat percentage over time. Athletes in weight-controlled sports or those who need to make weight for competitions can use these tests to determine a safe minimum body fat percentage, ensuring they do not fall below levels that might be harmful over extended periods.Some tests, such as DEXA scans, provide critical information beyond just body fat, including bone mineral density, total body water, and lean tissue mass, which are useful for evaluating training adaptations, especially in resistance training aimed at muscle hypertrophy.

The calculation of ideal body weight or fat mass from body fat measurements allows athletes to set realistic targets for weight or body fat percentage reduction, ensuring the goals are safe and achievable. This is crucial for planning and tracking progress towards attaining an optimal body composition for their sport. Ideal body weight (IBW) can be calculated as follows:

 IBW = (body weight – fat weight) / (1.00 – desired % / 100)

IBW = (215 lb – 32.3 lb) / (1.00 – 13% / 100)

IBW = 182.7 lb / (1.00 – 0.13)

IBW = 182.7 lb / 0.87

IBW = 210 lb

In the study of body composition measurement, there are no direct methods available; instead, these measurements are usually indirect estimates, each with its own set of pros and cons. The choice of measurement technique is influenced by various factors, including client needs, the evaluation’s purpose, cost, tool availability, technician training, and the relative advantages and disadvantages of each method. This article outlines several commonly used and practical body composition measurement techniques.

Height, Body Weight, and Body Mass Index (BMI) measurements are straightforward and can yield valuable body composition data. Height may vary throughout the day due to factors like spinal loading and vertebral disc volume and can decrease over a person’s lifetime. However, for adults, the slight daily fluctuations mean height doesn’t need to be measured frequently. Body weight measurements, on the other hand, are useful for monitoring changes, especially in weight loss or gain programs or for athletes managing weight for competition classes.

Height is ideally measured using a stadiometer, which is a wall-mounted vertical ruler with a horizontal headboard for accuracy. Less reliable are scales with attached rulers. Adhering to standard measurement procedures ensures reliability and accuracy: the subject removes shoes, stands straight with heels together against the wall, inhales deeply, holds it, and keeps their head level and eyes forward while the measurement is taken in inches or centimeters. Body weight and mass, though often measured similarly, are distinct. Body mass reflects the total matter within an object or person, while weight measures force, factoring in mass and gravitational acceleration. Measurements are typically expressed in kilograms for mass and pounds or Newtons for weight. Standardizing clothing and the time of day for measurements (preferably early morning) helps account for day-to-day variations due to meals, fluid intake, and bodily functions.

The equipment recommended for measuring body weight and mass is a calibrated physician’s scale, which provides the most accuracy. The procedure for obtaining these measurements involves the subject minimizing clothing for precision, removing shoes, emptying pockets, and removing jewelry. The subject’s weight or mass is recorded after the scale’s beam stabilizes, with weight noted in pounds and mass in kilograms.

Body Mass Index

Body Mass Index (BMI) is a widely used metric to assess body mass in relation to height, formulated as BMI (kg/m^2) = body mass (kg) / height squared (m^2). It’s a simple calculation that has become a standard tool for identifying the risk of diseases such as type 2 diabetes, hypertension, and cardiovascular disease (CVD). The BMI can also be calculated using pounds and inches through the equation: BMI = body weight (lb) × 703 / height^2 (in.^2). For instance, a 195-pound man who is 6 feet 3 inches tall would have a BMI of 24.4 kg/m^2, placing him within the normal range according to BMI standards set by the American College of Sports Medicine in 2007:

• Underweight: BMI < 18.5
• Normal: BMI 18.5 to 24.9
• Overweight: BMI 25 to 29.9
• Obese: BMI 30 to 39.9
• Morbid obesity: BMI > 40

While BMI calculation is straightforward and its application is particularly relevant in sedentary and clinical populations due to its strong correlation with disease risk, it faces criticism for being a poor predictor of body fat percentage and not accounting for weight distribution. This can lead to inaccurate classifications (normal, overweight, obese) especially in muscular individuals, athletes, and professional sports players.

Evidence of BMI’s limitations is highlighted in studies on athletes like those in the National Football League, where all players were classified as overweight, obese, or very obese by BMI standards, despite having body fat percentages ranging from 6.3 to 25.1%. Similarly, NCAA Division I American football players had an average BMI of 29.8 kg/m^2 but an average body fat of approximately 15%, showing the discrepancy between BMI and actual body composition. Additional studies support these findings, indicating that BMI tends to overestimate overweight and obese classifications in over half of the athletes assessed. Therefore, BMI is not considered a useful tool for measuring body composition in resistance-trained or athletic populations.

Waist-to-Hip Ratio

The waist-to-hip ratio (WHR) serves as an indicator of body fat distribution, distinguishing between apple and pear body shapes, and acts as a measure of general health. It compares the circumferences of the waist to the hip and is recognized as a factor in assessing disease risk. A notable advantage of WHR is its simplicity; it only requires a tape measure for administration, making it easily accessible. In certain cases, WHR can outperform BMI as a predictor of mortality, though it does not offer insight into the percentage of body fat. For a more precise estimation of body fat percentage, skinfold measurement or another body fat assessment technique is preferred. The accuracy and reliability of the WHR measurement greatly depend on the standardization of the circumference measuring technique.

Equipment necessary for WHR measurement includes a flexible tape measure, with the Gulick II tape measure being particularly advantageous due to its constant tension feature, which reduces variability between different examiners.

The procedure for measuring WHR involves several steps:

1. Use a flexible tape measure, ideally a Gulick II tape measure, to ensure consistent tension and reduce measurement variability.
2. Measure the waist circumference at its smallest point, usually about 1 inch (2.54 cm) above the navel.
3. Measure the hip circumference at the widest part of the buttocks, with the subject wearing minimal clothing to ensure accuracy.
4. Calculate the WHR by dividing the waist circumference (in cm or inches) by the hip circumference (in cm or inches). The ratio is unitless since the units cancel out during division.
5. Repeat the measurements until each is consistent to within 0.25 inches (0.6 cm) of one another, ensuring reliability.

The standards for evaluating WHR values are detailed in various resources and provide guidance on interpreting the measurements in the context of health risk assessments.

Skinfold Measurement

Skinfold measurement, a popular method for estimating percent body fat, achieves relative accuracy when performed by a trained technician using high-quality calipers, such as Lange or Harpenden, which exert a constant pressure of approximately 10 g/mm^2. This technique is based on the premise that the amount of subcutaneous fat is directly proportional to the overall body fat.

Following skinfold measurements, regression analysis, which involves predicting a dependent variable from one or more independent or predictor variables, estimates total body fat percentage. Utilizing the sum of skinfolds along with significant predictors like gender and age, regression analysis computes a prediction equation for body density and fat percentage. Assuming correct techniques and equations are employed, the variability in predicted body fat percentage from skinfold analysis is about ±3 to 5% (American College of Sports Medicine 2008).

The accuracy of skinfold measurement is contingent upon the application of prediction equations closely aligned with the demographic characteristics of the population under examination. The selection of measurement sites—three, four, or seven, depending on the regression equation—plays a crucial role in this process. Both seven-site and three-site skinfold equations have demonstrated similar standard errors of estimate among men (±3.4 to 3.6%) and women (±3.8 to 3.9%) (American College of Sports Medicine 2007).

Equipment Needed: High-quality calipers, such as Lange or Harpenden.

Procedure:

1. Choose the number of sites and corresponding equations based on the demographic characteristics of the tested population.
2. To measure, firmly grasp a skin fold with the thumb and index finger about 8 cm apart, lifting it away from the body while the subject is relaxed. Notable measurement sites include the abdomen, biceps, chest/pectoral, midaxillary, subscapular, suprailiac, thigh, and triceps.
3. Ensure that the measured tissue is subcutaneous fat, not skeletal muscle, possibly requiring a larger grasp for obese individuals.
4. Position the caliper’s jaws 1 cm below the fingers holding the fold, with the caliper facing upward.
5. Release the caliper grip and record the measurement within three seconds.
6. Perform measurements on the body’s right side, in duplicate or triplicate, to the nearest 0.5 mm. If discrepancies greater than 3 mm arise, an additional measurement may be necessary.
7. Rotate through the measurement sites instead of measuring the same site sequentially.
8. Sum and average the measurements from each site to estimate body density and percent body fat through a regression equation or prediction table.

It’s imperative to select a fitting prediction equation for accurate skinfold analysis. Over 100 regression equations, developed since the early 1950s, predict body density and fat percentage. Equations validated across various studies should be chosen based on factors like gender, age, ethnicity, and activity level. While general equations can provide accurate estimates for diverse population segments, incorporating quadratic and logarithmic terms has enhanced most regression equations’ accuracy. Upon determining body density, percent body fat is calculated using formulas like the Siri or Brozek equations.

Specific equations catering to various populations based on ethnicity, gender, and age have also been developed, underlining the need to select the most appropriate method for the population in question. Further resources, including tables for interpreting BMI measurements and percent body fat classifications, offer additional guidance on assessing body composition.

Girth Measurements

Girth measurements are taken to determine the circumference of body limbs or regions, offering insights into changes in muscle size from training and, when used with skinfold measurements, providing data on body composition. This method is straightforward, quick, inexpensive, and doesn’t require specialized tools. It can yield accurate estimates of percent body fat (±2.5 to 4%). Typically measured sites vary by age and gender, including the right upper arm, abdomen, right forearm, buttocks (hip), right thigh, and right calf across different groups.

Equipment Needed: A tape measure, with a Gulick II tape measure being preferred for its consistency in tension application.

Procedure:

1. Using the tape measure, apply it horizontally to the measurement site so it’s taut, reading the circumference to the nearest half centimeter with the subject in minimal clothing for accuracy.
2. Take duplicate measurements at each site, averaging them. If the readings vary by more than 5 millimeters, take another measurement.
3. Ensure the subject remains relaxed during measurements.
4. Correct tape placement is crucial for accurate measurement. For the chest, place the tape at the level of the fourth ribs with arms abducted, then measured upon arm adduction and at the end of respiration. For the shoulder, measure at the shoulders’ maximal circumference. For the abdomen, measure at its greatest circumference, often near the navel. The right thigh measurement is taken at its largest circumference below the gluteal fold, and the right calf at its largest midpoint between the knee and ankle. Waist and hip measurements involve the tape at the waist’s smallest point and the hips’ largest point, respectively. The right upper arm and forearm are measured at their midpoints and largest proximal area, respectively.

Estimation of Percent Body Fat: With the measurements obtained, age- and gender-specific equations can estimate percent body fat, utilizing constants derived from circumferences for young and older men and women. This estimation method has an accuracy range of ±2.5 to 4.0%.

Circumference Percent Body Fat Estimation Equations:

• Young men: Constant A + B – C – 10.2 = percent body fat
• Young women: Constant A + B – C – 19.6 = percent body fat
• Older men: Constant A + B – C – 15.0 = percent body fat
• Older women: Constant A + B – C – 18.4 = percent body fat

These equations, endorsed by the American College of Sports Medicine and outlined in the works of McArdle, Katch, and Katch (2007), offer a method for calculating percent body fat based on circumference measurements.

Hydro densitometry

Hydrodensitometry, also known as underwater or hydrostatic weighing, has long been regarded as the criterion method or gold standard for body composition analysis, despite being an indirect method. This technique relies on Archimedes’ principle, which states that a body immersed in water experiences a buoyant force equal to the weight of the water displaced by the body. By comparing an individual’s land weight to their underwater weight, the displaced water’s weight is determined, allowing for the calculation of body density. Since fat has a lower density than water, and lean tissue mass a higher one, this method can accurately estimate body fat percentage.

Lean tissue density varies among different populations, affecting hydro densitometry’s accuracy. African Americans, Hispanics, and Caucasians have been shown to possess different average lean tissue densities. Additionally, children, older adults, and those with significant muscle mass from resistance training may have variations in body density that can impact the estimation of percent body fat.

The procedure for hydro densitometry involves subjects wearing minimal clothing and being weighed while fully submerged in a tank or pool equipped with a scale or force transducer. Various factors, such as residual lung volume, water temperature, and gastrointestinal gas, must be accurately accounted for to ensure precision in the measurements.

Equipment Needed:

• A tank or pool made from materials such as stainless steel, fiberglass, ceramic tile, or Plexiglas, with dimensions that accommodate full submersion of an individual.
• A scale or force transducer with a seat to weigh individuals underwater.

Procedure:

1. Subjects prepare by wearing tight-fitting swimwear, removing jewelry, and ensuring they are not full from recent meals or have gas-inducing foods in their system. It’s also recommended for women to avoid testing around their menstruation period due to potential water weight gain.
2. Land weight is measured and recorded.
3. In the water, subjects expel air, minimize trapped air, and assume a seated position with minimal movement.
4. Multiple underwater weights are recorded, with the highest or the average of the top three used for analysis.
5. Residual lung volume is either directly measured or estimated based on the subject’s height and age.
6. Body density is then calculated and converted to percent body fat using formulas like the Siri or Brozek equations, or population-specific equations for more accurate adjustments based on ethnicity, age, and gender.

While hydro densitometry offers high reliability and has served as a benchmark for validating other body composition measurement tools, it has practical limitations. These include the cost and complexity of the required equipment, the time-consuming nature of the tests, and discomfort or fear from subjects about being fully submerged in water. Despite these challenges, hydro densitometry remains a foundational tool in body composition analysis, particularly for research and clinical settings.

Bioelectrical Impedance Analysis

Bioelectrical impedance analysis (BIA) provides a noninvasive, straightforward method for assessing body composition by measuring the body’s electrical conductivity, which reflects the fat-free tissue mass. Lean tissues, rich in water and electrolytes, conduct electricity well and show low impedance, while fat tissue does not conduct electricity as effectively. BIA devices introduce a small electrical current through the body (from ankle to wrist) and measure the resistance encountered, allowing for the estimation of body fat percentage and total body water. Both single-frequency and multi-frequency BIA devices exist, with the latter offering more nuanced insights into different body fluid compartments.

Equipment: Commercially available BIA analyzers vary in complexity and price, offering options for different settings and needs.

Procedure:

1. Calibration of the BIA device as per the manufacturer’s guidelines.
2. The subject should lie on a nonconductive surface, keeping limbs separate from the body.
3. Cleaning of the right hand, wrist, foot, and ankle with alcohol pads, followed by drying.
4. Placement of electrodes on specific sites on the right hand and foot, with reference electrodes on the right wrist and ankle.
5. The BIA device applies a current and calculates impedance and body fat percentage.
6. Modern BIA devices may simply require standing on a platform or holding the device, with automated instructions for the subject.
7. For dry feet, which can cause measurement errors, a slight moistening may be necessary.

Accuracy and reliability of BIA are influenced by the device’s specific equations, which consider factors like gender, age, race or ethnicity, and physical activity levels. Proper testing conditions are crucial; subjects should not eat, drink, exercise, or consume alcohol or diuretics for specific periods before the test. Dehydration, glycogen levels, and physiological conditions like menstruation can affect the measurements.

While BIA is validated against gold standard methods like hydrodensitometry, it may overestimate body fat in lean individuals and underestimate it in obese subjects or athletes. The accuracy of BIA also depends on the technical execution, the prediction equations used, and the specific device. Consistent use of the same BIA unit over time can improve the reliability of measurements.

Air displacement plethysmography

Air displacement plethysmography (ADP) measures body volume by displacing air rather than water, presenting a noninvasive, safe, and quick method that accommodates all individuals comfortably. The BOD POD, a commercial ADP system, features a dual-chamber plethysmograph with a subject test chamber and a reference chamber, integrated with an electronic scale, computer, and software system. It determines body volume based on the difference in air volume in the chamber with and without the subject.

Despite its advantages, ADP’s major drawback is the high cost of the ADP unit. Errors in ADP measurements can arise from various factors, including non-fasting subjects, unaccounted air in the lungs or trapped in clothing and body hair, moisture on the body, and elevated body temperature. Yet, ADP’s reliability and validity have been affirmed through comparisons with hydrodensitometry and dual-energy X-ray absorptiometry (DXA), showing good outcomes in assessing body composition changes during weight loss in populations like collegiate female athletes and wrestlers. However, discrepancies have been observed, with ADP occasionally overestimating or underestimating percent body fat in specific groups.

Equipment Required:

• An ADP unit, such as the BOD POD.

Procedure:

1. Enter the subject’s details into the BOD POD computer.
2. Calibrate the BOD POD as per the manufacturer’s guidelines.
3. Prepare the subject by ensuring they wear minimal clothing, such as swimsuits or compression shorts, and remove items like jewelry and glasses. Not wearing a swim cap, especially if hair covers a significant part of the face, may lead to underestimation of percent fat.
4. Measure the subject’s mass using the BOD POD’s digital scale.
5. Have the subject sit in the chamber for the test, where at least two measurements are taken to ascertain body volume, aiming for readings within 150 ml of each other.
6. Measure or predict thoracic gas volume, employing the panting method where necessary, to ensure accurate body volume calculations.
7. Finally, calculate the corrected body volume (raw body volume minus thoracic gas volume), determine body density, and estimate percent body fat using prediction equations similar to those in hydrodensitometry.

This streamlined procedure and the technological advantages of ADP make it an effective tool for body composition analysis, offering a viable alternative to more invasive or uncomfortable methods, despite its higher cost and potential measurement errors.

Dual-Energy X-Ray Absorptiometry

Dual-energy X-ray absorptiometry (DXA) has gained popularity as a tool for body composition measurement, providing data on percent body fat, bone mineral density, and lean tissue mass both regionally and for the total body. DXA works on the principle of differential X-ray attenuation at two energies as they pass through the body, enabling the estimation of soft tissue composition and bone mineral content.

Equipment Required:

• A DXA machine, which includes a low-current X-ray tube, a detector on the scanning arm, and a computer interface for image scanning.

Procedure:

1. Calibration of the DXA machine using a calibration block is essential for quality assurance and accurate readings.
2. The subject’s information must be entered into the DXA software program before the scan.
3. Subjects should wear regular, metal-free clothing; shorts and a T-shirt are recommended.
4. Proper positioning of the subject on the scanning table is crucial, with the body aligned and centered according to specific guidelines and limbs secured to minimize movement.
5. The scanning process involves the subject lying still while a rectilinear scan is performed from head to toe, which can last between 5 to 25 minutes based on the scan type and the subject’s size.
6. After scanning, the technician outlines regions of interest in the software to accurately assess regional body composition.
7. The DXA report provides detailed data on regional and total-body bone mass, lean tissue mass, and fat mass.

DXA offers many advantages, including ease of administration, speed, accuracy, and comfort for most subjects, with minimal radiation exposure. It allows for regional measurements, appealing to various populations.

However, DXA has limitations, such as the inability to accommodate very large individuals and the high cost of the equipment. The need for a physician’s prescription in some regions, assumptions about constant hydration, potential errors in body thickness measurement, and the importance of consistent technician operation highlight some of its practical challenges. Additionally, standardization issues among DXA manufacturers may affect the comparability of results across different machines.

Despite these limitations, DXA has demonstrated a high correlation with hydrodensitometry and other body composition methods, often showing slightly higher body fat percentages. Although considered accurate, these limitations prevent DXA from being the definitive gold standard in body composition measurement at this time.