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40-537: Resting metabolic rate generally composes 60 to 75 percent of TDEE. Because adipose tissue does not use much energy to maintain, fat free mass is a better predictor of metabolic rate. A taller person will typically have less fat mass than a shorter person at the same weight and therefore burn more energy. Men also carry more skeletal muscle tissue on average than women, and other sex differences in organ size account for sex differences in metabolic rate. Obese individuals burn more energy than lean individuals due to increase in

80-414: A definition. When referring to this meaning, gold standard tests are normally not performed at all. This is because the gold standard test may be difficult to perform or may be impossible to perform on a living person (i.e. the test is performed as part of an autopsy or may take too long for the results of the test to be available to be clinically useful). Other times, the "gold standard" does not refer to

120-472: A female thirty year old will have a different ideal fat percentage than a male thirty year old. An athlete will have a different ideal than a non athlete, and it can depend on the sport. The physical activities which can help decrease fat mass, increase lean mass, or both are the same for everybody. Aerobic exercise, also known as cardio (heart) exercise, decreases fat. High intensity interval training (HIIT) in particular helps decrease visceral fat. Visceral fat

160-477: A magnetic field to the body and measures the difference in relaxation rates of hydrogen atoms within fat versus lean mass. It functions similarly to magnetic resonance imaging (MRI) but instead of providing an image like MRI, QMR gives quantities of fat mass, lean mass, and total body water. QMR is also widely used for body composition analysis of animals, including laboratory animals like mice, and wildlife including birds. Assessment of somatic (skeletal) protein

200-412: A test becomes popular and is declared to be the gold standard without adequate consideration of alternatives or despite weaknesses. As new diagnostic methods become available, the "gold standard" test may change over time. For instance, for the diagnosis of aortic dissection , the gold standard test used to be the aortogram , which had a sensitivity as low as 83% and a specificity as low as 87%. Since

240-436: Is bioelectrical impedance analysis (BIA), which uses the resistance of electrical flow through the body. 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. By controlling hydration status or performing multiple impedance measurements, it is possible to estimate body fat and other variables. InBody developed

280-402: Is a direct application of Archimedes' principle, that an object displaces its own volume of water. Air displacement plethysmography is an alternative to underwater weighing for measuring body volume. The technique uses air as opposed to water and is known as air displacement plethysmography (ADP). Subjects enter a sealed chamber that measures their body volume through the displacement of air in

320-484: Is a leading factor in regulating appetite and energy intake in humans. Formulas have been devised to estimate energy expenditure in humans, but they may not be accurate for people with certain illnesses or the elderly. Not all formula are accurate in overweight or obese individuals. Wearable devices can help estimate energy expenditure from physical activity but their accuracy varies. Fat free mass In physical fitness , body composition refers to quantifying

360-421: Is a naturally occurring radioactive isotope found in intracellular water, but is not present in stored triglycerides (fat). Whole body counting can measure the amount of potassium 40 (40K) in the body, a quantity called total body potassium (TBK). This can be used to estimate fat-free mass directly. It has mostly been replaced by newer, more accurate techniques such as DEXA. Another method to estimate body water

400-486: Is a technique used for measuring body shape. Initially, BVI technology employed white light scanning machines to measure an individual's body shape. However, recent technological advances in 3D measurement have enabled BVI to be calculated using images taken on a smartphone. Two images are required to create an individual 3D silhouette. By comparing this 3D silhouette with MRI data, body volume and fat distribution can be calculated. Body composition can also be measured using

440-400: Is especially important when a perfect test is available only by autopsy. A test has to meet some interobserver agreement, to avoid some bias induced by the study itself. Calibration errors can lead to misdiagnosis . Sometimes "gold standard test" refers to the best-performing test available. In these cases, there is no other criterion against which it can be compared and it is equivalent to

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480-529: Is near the internal organs, while subcutaneous fat is just under the skin. The former is more tightly associated with poor metabolic health. Bone and muscle strengthening exercise, also known as resistant training, decreases fat mass and increases lean mass at the same time, though it does better at the latter. In order to prevent injury from repetitive motion, people should do resistant training with different parts of their bodies on different days. Gold standard (test) In medicine and medical statistics ,

520-446: Is the amount of energy burned digesting food, around 10 percent of TDEE. Proteins are the component of food requiring the most energy to digest. Losing or gaining weight affects the energy expenditure. Reduced energy expenditure after weight loss can be a major challenge for people seeking to avoid weight regain after weight loss. It is controversial whether losing weight causes a decrease in energy expenditure greater than expected by

560-446: Is typically determined by simple measurements and calculations, including mid-arm circumference (MAC), mid-arm muscle circumference (MAMC), and creatinine height ratio (CHI). Creatinine height ratio is calculated as 24-hour urine creatinine multiplied by 100 over the expected 24-hour urine creatinine for height. This calculation results in a percentage that can indicate protein depletion. Many methods of determining body composition use

600-473: The Archives of Biological Medicine and Rehabilitation specifies this usage. In practice, however, the uptake of this term by authors, as well as enforcement by editorial staff, is notably poor, at least for AMA journals. When the criterion is a whole clinical testing procedure it is usually referred to as clinical case definition . Differing case definitions can produce wildly different results when used as

640-457: The body weight as a measurement, determined via a weighing scale . Other details such as height and age can be correlated with other measures and are often used in estimation formulas. The methods above are each valid and notable in providing a measurement that can be used to determine the "true body composition" of the tested individual. However, each method does possess its own individual limitations, such as accuracy, precision, or expense, and

680-498: The gold standard , criterion standard , or reference standard is the diagnostic test or benchmark that is the best available under reasonable conditions. It is the test against which new tests are compared to gauge their validity, and it is used to evaluate the efficacy of treatments. The meaning of "gold standard" may differ between practical medicine and the statistical ideal. With some medical conditions, only an autopsy can guarantee diagnostic certainty. In these cases,

720-479: The "gold standard" test of a medication or procedure is whether or not it leads to an increase in the number of neurologically intact survivors that walk out of the hospital. Other types of medical research might regard a significant decrease in 30-day mortality as the gold standard. The AMA Style Guide has preferred the phrase criterion standard instead of "gold standard." Other journals have also issued mandates in their instructions for contributors. For instance,

760-502: The 4-compartment model consists of a weight measurement, body density measurement using hydrostatic weighing or air displacement plethysmography , total body water calculation using isotope dilution analysis, and mineral content measurement by dual-energy X-ray absorptiometry (DEXA). However, it is also common to use a DEXA scan alone and refer to this as the "gold standard". These claims are somewhat dubious since measurements methods vary significantly from study to study. In practice,

800-412: The accuracy of BIA machines. BIA machines have found acceptance in medical, fitness, and wellness space owing to their ease-of-use, portability, quick measurements, and cost efficiency. AURA Devices developed and launched a number of wearable bioimpedance trackers, including the first smart strap for Apple Watch that tracks body fat, muscles, lean mass, water levels, etc. The Body Volume Index (BVI)

840-430: The advancements of magnetic resonance imaging , the magnetic resonance angiogram (MRA) has become the new gold standard test for aortic dissection, with a sensitivity of 95% and a specificity of 92%. Before the widespread acceptance of any new test, the former test retains its status as the "gold standard". Because tests can be incorrect (yielding a false-negative or a false-positive ), results should be interpreted in

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880-426: The advantage of being able to also directly measure muscle thickness and quantify intramuscular fat. In the abdomen, ultrasonography is a useful tool for quantifying both subcutaneous and visceral fat. Ultrasonography has many advantages over CT scan and MRI as it is non-invasive and doesn't utilize ionizing radiation, making it more accessible to special populations. Quantitative magnetic resonance (QMR) applies

920-466: The amount of calories needed to maintain adipose tissue and other organs that grow in size in response to obesity. At rest, the largest fractions of energy are burned by the skeletal muscles, brain, and liver; around 20 percent each. Increasing skeletal muscle tissue can increase metabolic rate. Energy burned during physical activity includes the exercise activity thermogenesis (EAT) and non-exercise activity thermogenesis (NEAT). Thermic effect of food

960-509: The basis for evalulating a given diagnostic method. A hypothetical ideal "gold standard" test has a sensitivity of 100% concerning the presence of the disease (it identifies all individuals with a well-defined disease process; it does not have any false-negative results) and a specificity of 100% (it does not falsely identify someone with a condition that does not have the condition; it does not have any false-positive results). In practice, there are no true gold standard tests. Sometimes

1000-403: The best-performing test available, but the best available under reasonable conditions. For example, in this sense, an MRI is the gold standard for brain tumor diagnosis, though it is not as good as a biopsy. In this case, the sensitivity and specificity of the gold standard are not 100% and it is said to be an "imperfect gold standard" or "alloyed gold standard". The term ground truth refers to

1040-401: The body. Common models include: As a rule, the compartments must sum to the body weight. The proportion of each compartment as a percent is often reported, found by dividing the compartment weight by the body weight. Individual compartments may be estimated based on population averages or measured directly or indirectly. Many measurement methods exist with varying levels of accuracy. Typically,

1080-425: The chamber. Next, body volume is combined with body weight (mass) 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). Total body water may be effectively measured using isotope dilution analysis of deuterium oxide. Potassium 40

1120-426: The combination of methods also has limitations. Often, the relative change from one period to the next is most important; if an individual can maintain all factors as similar as possible, even a simple method such as weighing may give enough information to determine the true change in composition. The ideal percent of body mass which should be fat depends on an individual's sex, age, and physical activity. For example,

1160-400: The context of the history, physical findings, and other test results of the individual being tested. It is within this context that the sensitivity and specificity of the "gold standard" test is determined. When the gold standard is not a perfect one, its sensitivity and specificity must be calibrated against more accurate tests or against the definition of the condition. This calibration

1200-493: The different components (or "compartments") of a human body . The selection of compartments varies by model but may include fat , bone , water , and muscle . Two people of the same gender, height, and body weight may have completely different body types as a consequence of having different body compositions. This may be explained by a person having low or high body fat , dense muscles, or big bones. Body composition models typically use between 2 and 6 compartments to describe

1240-535: The earliest weight loss drugs, 2,4-dinitrophenol and thyroid hormone , increase energy expenditure, but both were withdrawn from use due to risks. Adrenergic agonists , especially those that work on the beta-2 adrenergic receptor , increase energy expenditure. Although some such as clenbuterol are used without medical approval for weight loss, none have achieved approval for this indication due to cardiac risks. Other drugs such as atypical antipsychotics are believed to reduce energy expenditure. Energy expenditure

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1280-443: The gold standard test is the best test that keeps the patient alive, and even gold standard tests can require follow-up to confirm or refute the diagnosis. The term 'gold standard' in its current sense in medical research was coined by Rudd in 1979, in reference to the monetary gold standard. "Gold standard" can refer to popular clinical endpoints by which scientific evidence is evaluated. For example, in resuscitation research,

1320-424: The higher compartment models are more accurate, as they require more data and thus account for more variation across individuals. The four compartment model is considered the reference model for assessment of body composition as it is robust to most variation and each of its components can be measured directly. A wide variety of body composition measurement methods exist. The gold standard measurement technique for

1360-545: The loss of adipose tissue and fat-free mass during weight loss. This excess reduction is termed adaptive thermogenesis and it is estimated that it might compose 50 to 100 kcal/day in people actively losing weight. Some studies have reported that it disappears after a short period of weight stability, while others report longer-lasting effects. Increasing exercise is recommended as a way to increase energy expenditure in individuals seeking to lose weight. Some drugs used for weight loss work by increasing energy expenditure. Two of

1400-573: The measurement methods used will be a tradeoff between cost, availability, and accuracy. Body composition measurement with dual energy X-ray absorptiometry (DEXA) is used increasingly for a variety of clinical and research applications. A DEXA scan requires medical supervision by a radiologist. Total body scans using DEXA give accurate and precise measurements of body composition, including bone mineral content (BMC), bone mineral density (BMD), lean tissue mass, fat tissue mass, and fractional contribution of fat. DEXA measurements are highly reproducible if

1440-458: The role of DEXA in clinical evaluations and research studies has been questioned by Wang et al. who stated that "the errors of the DXA [DEXA] method are still of concern if it were to be used as the criterion." Hydrostatic weighing, also referred to as underwater weighing, hydrostatic body composition analysis and hydrodensitometry, is a technique for measuring the density of a living person's body. It

1480-459: The same type of machine is used, making them excellent for monitoring pharmaceutical therapy, nutritional or exercise intervention, sports training, and other body composition altering programs. They are also fast, simple, non-invasive, and expose the subject to a level of x-rays less than that of a cross-country flight. DEXA exams provide both total body and up to 14 regional (trunk, individual arms & legs, android, gynoid, etc.) results. However,

1520-549: The skin fold test, which is performed using a measuring caliper . It can be done in nine steps: A common skin fold method is by using gun style calipers to measure the thickness of subcutaneous fat in multiple places on the body. This includes the abdominal area, the subscapular region, arms, buttocks and thighs. These measurements are then used to estimate total body fat. Ultrasound has also been used to measure subcutaneous fat thickness, and by using multiple points an estimation of body composition can be made. Ultrasound has

1560-400: The underlying absolute state of information; the gold standard strives to represent the ground truth as closely as possible. While the gold standard is the best effort to obtain the truth, ground truth is typically collected by direct observations. In machine learning and information retrieval , "ground truth" is the preferred term even when classifications may be imperfect; the gold standard

1600-404: The world's first 8-point tactile electrode system in 1996, a direct segmental analysis method that measures the impedance of five torsos using multiple frequencies. Many BIA products provide partial muscle and fat mass measurements, but not impedance, especially in the torso. Recent advancements such as 8-point electrodes, multi-frequency measurements, and Direct Segmental Analysis, have improved

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