What is body composition is best described as?

BODY COMPOSITION

J.R. Lustig, B.J.G. Strauss, in Encyclopedia of Food Sciences and Nutrition (Second Edition), 2003

Cellular

The cellular level of body composition consists of body cells (body cell mass) and their surrounding extracellular water, plus the skeleton and connective tissue. Although there is some lipid in the form of cell membranes, this compartment is largely fat-free and these components are sometimes termed the fat-free mass (FFM) or in older terminology the lean body mass (LBM). The body cell mass is responsible for almost all of the basal energy expenditure of the body, since that is where cellular metabolic and respiration processes take place. Together with the adipose tissue compartment (which consists mostly of fat), this level is often referred to as a two-compartment model, i.e., FFM and fat mass (FM). In the healthy individual, the FFM has a relatively constant composition, with a water content of 7274%, an average density of 1.1gcm3 at 37°C, a potassium content of 6070mmolkg1 in men and 5060mmolkg1 in women, and a protein content of 20%.

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Ageing and changes in body composition: the importance of valid measurements

P. Deurenberg, M. Deurenberg-Yap, in Food for the Ageing Population, 2009

9.1 Introduction

Body composition has long interested mankind. Centuries ago the Greeks dissected human cadavers to get an insight into the structure and build of the body, and drawings from the Middle Ages of gross muscle structure are still famous today, not only from the artistic point of view. With the development of analytical chemistry last century, it was inevitable that this new knowledge would be applied to body tissues, leading to complete human cadavers being analysed chemically. Starting with analysis of foetuses and the cadavers of newborns around 1900 (Camerer and Söldner, 1900), the most important work of chemical analysis in adult cadavers was performed in the middle of last century (Mitchell et al., 1945; Widdowson et al., 1951). It was found that the variation in chemical composition between individuals was remarkably reduced if data were expressed per unit fat free mass (FFM), and since then FFM (= body weight minus body fat) is generally used to standardise amounts of components in the body. The chemical analysis of human cadavers laid the groundwork for many other, non-invasive (in vivo) methods of body composition and today we can tap from a scala of methodologies, ranging from simple body measures as weight and height and skinfold thickness to predict body composition to sophisticated radiological or nuclear methods that actually measure components of body composition (Forbes, 1987; Heymsfield et al., 2005). With the widespread availability of methods and instruments, body composition measurements can easily be incorporated in research or clinic (Jebb and Elia, 1993), but unfortunately not every user is aware of the limitations of the methodologies, sometimes leading to wrong interpretations and conclusions (Deurenberg and Roubenoff, 2002).

From conception to old age, body composition is constantly changing (Forbes, 1987), and it is changing at atomic, molecular, cellular, tissue and whole body level (Wang et al., 1992). It is important to understand those changes at all levels to be able to interpret body composition measurements correctly. Many body composition methods use assumptions to convert the actual body measurement into aspect(s) of body composition. Awareness of these assumptions and their limitations is a must for correct interpretation of results.

There have been a number of recent publications covering body composition in elderly (Baumgartner, 2000; Harris, 2002; Pierson, 2003; Villareal et al., 2005). This chapter will briefly describe the most important changes in body composition with age, especially at old age, and describe a number of often used methodologies to measure these aspects of body composition (or their change) with their advantages and limitations.

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Physical and Clinical Assessment of Nutrition Status

Edward Saltzman, Kris M. Mogensen, in Nutrition in the Prevention and Treatment of Disease (Third Edition), 2013

III Body Composition Assessment

Body composition describes and quantifies various compartments within the body. Fat content of the body is expressed as a percentage of total body mass or as absolute FM. Body composition can be assessed at the level of the body as a whole (e.g., weight or BMI); by division into FFM and FM; by division into molecules such as water, protein, and fat; or at an atomic level into elements such as carbon and potassium (Figure 3.3). Methods to assess body composition vary by the compartments being measured. Some commonly employed methods include DXA, which can divide the body into fat, fat-free, and bone compartments, and density methods such as air displacement plethysmography (ADP; using a device known as the BOD POD) and hydrostatic weighing or underwater weighing and dilution methods that measure body water. These methods utilize body density, body volume, and weight to estimate fat and fat-free compartments. Hydrostatic weighing was the traditional gold standard but has been replaced by ADP and DXA. Bioelectrical impedance (BIA) measures body water, from which FFM can be estimated. The primary use for DXA on a clinical basis is to provide a measure of bone density in order to assess osteoporosis risk, but measures of fat and FFM are not clinically available. Of the methods discussed, BIA is the least accurate for individuals, but due to its ease of use and the low expense of some devices, it has become popular in weight loss programs and health clubs.

Figure 3.3. Models of body composition compartments.

ECF, extracellular fluid; ECS, extracellular solid.

From Ellis, K.J. (2000). Human body composition: In vivo methods. Physiol. Rev. 80, 649680. Used with permission.

Although excess adiposity is associated with disease in virtually every organ system, no universally agreed upon criteria for excess body fat has been accepted. The fat mass index (FMI; calculated as fat mass/height2) has been proposed as a useful measure of adiposity that is independent of FFM. FMI has been validated by comparison to body composition techniques as well as BMI in NHANES [50], but its utility as a measure to predict health outcomes awaits further investigation.

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Texture modification of food for elderly people

E. Rothenberg, K. Wendin, in Modifying Food Texture, 2015

7.2.2.1 Nutritional status

Body composition gives important information about a persons nutritional status. It can be measured by different techniques where the most simple is anthropometry. However, more sophisticated techniques such as dual X-ray absorptiometry can give in-depth information on the amounts of compositions as well as relationships between body compartments (Kyle et al., 2004; Tengvall et al., 2009). Age-related body composition change starts in early middle age, signified by a continuous loss of body water, bone content, fat-free mass, skeleton muscle mass and function and an increase in body fat, mainly visceral. However, a great variation exists among individuals of the same chronological age. Body mass index (BMI), calculated based on ones body weight and height (kg/h2), has been used as a useful indicator of body composition change. For most individuals both body weight and height decrease by age. However, regarding BMI a revised epidemiology is present, meaning that low BMI and weight loss are significant risk factors for all causes of mortality but elevated BMI and high proportion of body fat seem to have no harm but even a protective role on health and survival (Al Snih et al., 2007; Batsis et al., 2014; Flicker et al., 2010; Vischer et al., 2009). BMI is a proxy measure for energy stores and for older adults these stores seem to be beneficial. The cardiovascular risk by overweight appears to diminish by age. It has been shown that higher BMI (2530) is associated with greater disability-free life expectancy compared to groups of lower and higher BMI (Al Snih et al., 2007). Skeletal muscle mass is of great importance for physical function but also for immune function. Some individuals preserve muscle mass up to very high ages but others develop a progressive and irreversible reduction of muscle mass and strength (Buffa et al., 2011), due to the reduction the number of motoneurones and atrophy of muscle fibers. This phenomenon is named as sarcopenia (Figure 7.1) (Cruz-Jentoft et al., 2010). To maintain muscle mass and physical function physical exercise is of outmost importance. Being sedentary has been shown to increase the risk of mortality.

Figure 7.1. Mechanisms of sarcopenia.

Cruz-Jentoft et al. (2010).
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Feline Obesity

Alexander German, Sarah Heath, in Feline Behavioral Health and Welfare, 2016

Assessing Body Weight and Composition

Body composition can be assessed in various ways. First, dual-energy x-ray absorptiometry (DXA) is known to be precise and reliable and can be used in a referral setting84,85; however, it is not widely available in first opinion veterinary practice. Instead, noninvasive methods are preferred, most notably using a combination of body weight and body condition scoring (BCS). Body weight is best measured using the same set of electronic weigh scales, and it is important to calibrate these regularly. The most reliable calibration method is to use test weights, although, given the expense, any object of known mass could instead be used (e.g., a bag of food).

Although body weight is a poor measure of body composition, since it does not enable fat mass to be differentiated from lean tissue or bone mineral, it is the most precise means of monitoring a weight loss plan. Therefore, body weight should be measured at the outset and regularly thereafter. A variety of systems for assessing body condition are available, all of which use both visual assessment and palpation to determine body fat mass subjectively.86,87 However, the 9-integer-unit system is preferred. With appropriate training, the technique correlates well with body fat mass determined by other methods, such as DXA.86 At the outset, BCS can be used to establish the degree of obesity and predict the likely ideal weight of a particular animal (see below).86,87 BCS should also be used periodically during the weight program to check on progress, and target weight should be adjusted if required.

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Genes and Obesity

Anthony G. Comuzzie, ... Shelley Cole, in Progress in Molecular Biology and Translational Science, 2010

I Introduction

Body weight and composition are archetypical representations of complex phenotypes. This complexity arises from the contribution of environmental and genetic factors combined with a variety of interaction effects. These interactions include environment-by-environment, gene-by-gene, and gene-by-environment. All of these factors act and interact to produce variation in body weight and fat mass. While clinical obesity, generally defined in Western countries as a body mass index (BMI) 30kg/m2, represents a serious public health issue, the impact of genetics on body weight and composition is not limited to the clinical extremes. Indeed, it can be cogently argued that the clinical manifestation of obesity merely represents one end of the continuum of body weight distribution in a population. While the clinical definition of obesity may be useful for the assessment of health risks and decisions regarding intervention, its placement at any particular body weight is somewhat arbitrary. Therefore, understanding the genetic contribution to variation in body weight and composition, as well as adipose tissue function, is essential for understanding the biology underlying the clinical manifestation known as obesity and its relationship to other chronic diseases such as type 2 diabetes and heart disease.

According to the World Health Organization (WHO), the increasing prevalence of obesity worldwide contributes negatively to the overall public health by increasing an individual's risk for the development of a number of serious comorbidities (e.g., type 2 diabetes, heart disease, and cancer).1 Current estimates indicate that almost 70% of adults in the United States are overweight. The recent increase in obesity prevalence may be attributed to environmental changes, primarily characterized by increased availability of cheap and energy-dense foods, along with an increasingly sedentary lifestyle. Nevertheless, the effect on obesity is more pronounced in individuals who are genetically susceptible to these environmental insults. Hence, it is likely to be the response of an individual's genetic background to a given environment that determines susceptibility to obesity.

Gene mapping studies undertake to localize genes that influence the variation in phenotypes associated with disease risk.2Figure 1 shows the types of approaches taken to identify the genetic contribution to prevalent complex metabolic diseases such as obesity. Candidate gene studies, genome-wide linkage studies, and genome-wide association studies (GWASs) have been used to decipher the effect of genetics on obesity. Of late, GWASs have been increasingly used to identify the genetic variation underlying disease phenotypes.3 This chapter discusses the results of genetic mapping studies of obesity in human populations.

Fig. 1. Genetic study approaches.

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