Déficit androgénique: effet de la substitution sur la composition corporelle

Male hypogonadism is responsible for an increase in fat body mass and a decrease in lean body mass. Similar changes are observed in aging men. Aging is also frequently associated with a decrease in testicular function. Androgen replacement therapy in adult men with hypogonadism has been shown to reverse these changes in body composition. Androgens stimulate protein synthesis, especially in muscles, leading to a gain of muscle mass and muscle strength. In contrast, androgen therapy inhibits tissue utilization of lipids, predominantly in visceral fat and consecutively induces a decrease in fat body mass. As the same changes in body composition are observed in aging and in hypogonadal adult men, the value of androgen replacement therapy was evaluated in aging men with an age-related decrease in androgen production. About ten studies have included human males over the age of 65. The results obtained indicate the benefit of such therapy in terms of improvement in body composition in aging men due to a rise in plasma testosterone levels up to the normal range of young adult men.     

生物人类学和人体组成学的渊源关系

随着人体组成学中文版的发行和人体组成测量培训班在中国的举行, 中国生物人类学家对人体组成测量方法在科研中的运用有了更大的兴趣。该文对人类学家,如Jindr?ich Matiegka和Stanley MarionGarn在人体组成学发展中的历史贡献做了基本的介绍。此外, 作者还以Garn博士的工作为例, 去激励中国生物人类学家开展人体组成学的研究工作。文章讨论了人体组成成分的测量方法在生物人类学中的用途, 并介绍了人体组成学的基本理论和概念及近年来人体组成学的变化: 如影像技术的发展, 影像技术作为"金标准"对评估其他人体组成测量方法的用途, 双能量x线吸收法的优势, 生物电阻分析法的广泛运用, 和多种人体组成测量方法相辅相成的现象。作者对常用的人体组成测量方法的优缺点做了比较, 并指出人体组成成分测量是人体测量方法的自然延续, 人体组成学和生物人类学的关系渊源已久; 因此中国人类学家应当更多地利用人体组成测量方法对人体差异做更深入的研究, 并注重人体差异同健康疾病和生物医学的关系, 以便让生物人类学更好地为当今社会服务。     

Body composition and peak aerobic power in male international level Hungarian athletes

Body size, physique, body composition and physiological performance of elite athletes are independent aspects, have aroused the interest of exercise scientists, but studies that combine these aspects in elite athletes are scarcely available. The aim of the present study was to describe the selected anthropometric and exercise physiological characteristics of some Hungarian top athletes. The investigated subjects were qualified Hungarian water polo players (n=25), paddlers (n=24) and modem pentathlonists (n=20), all of whom had been medalists at several continental and intercontinental competitions. The athletes' body composition was estimated by the Drinkwater-Ross (45) body mass fractionation technique. Peak physiological performance was estimated by graded exhausting spiroergometric treadmill exercise. Intergroup differences in mean height, body mass and body composition characteristics were significant at the 5% level of random error. By the results of spiroergometry, all the three groups compared could be qualified as physically excellently trained. The greatest oxygen uptake relative to body mass was found in the modern pentathlonists (73.22 ml x kg(-1) x min(-1)) and the lowest one (59.79) in the water polo players. The authors do not disregard the favourable effects of regular and adequate trainings in the development of the studied characteristics, but in their opinion the process of proper selection has been the most important factor that explains the observed significant intergroup differences.     

Fat mass deposition during pregnancy using a four-component model.

Estimates of body fat mass gained during human pregnancy are necessary to assess the composition of gestational weight gained and in studying energy requirements of reproduction. However, commonly used methods of measuring body composition are not valid during pregnancy. We used measurements of total body water (TBW), body density, and bone mineral content (BMC) to apply a four-component model to measure body fat gained in nine pregnant women. Measurements were made longitudinally from before conception; at 8-10, 24-26, and 34-36 wk gestation; and at 4-6 wk postpartum. TBW was measured by deuterium dilution, body density by hydrodensitometry, and BMC by dual-energy X-ray absorptiometry. Body protein was estimated by subtracting TBW and BMC from fat-free mass. By 36 wk of gestation, body weight increased 11.2 +/- 4.4 kg, TBW increased 5.6 +/- 3.3 kg, fat-free mass increased 6.5 +/- 3.4 kg, and fat mass increased 4.1 +/- 3.5 kg. The estimated energy cost of fat mass gained averaged 44,608 kcal (95% confidence interval, -31, 552-120,768 kcal). The large variability in the composition of gestational weight gained among the women was not explained by prepregnancy body composition or by energy intake. This variability makes it impossible to derive a single value for the energy cost of fat deposition to use in estimating the energy requirement of pregnancy.     

生物阻抗技术概述

简要叙述了人体组织阻抗特性、生物阻抗技术的基本原理和测量方法,全面介绍了生物阻抗技术在细胞测量、体积测量、人体组织结构分析、组织监测、人体成分分析、生物阻抗成像等各方面的应用。     

The dynamics of human body weight change

An imbalance between energy intake and energy expenditure will lead to a change in body weight (mass) and body composition (fat and lean masses). A quantitative understanding of the processes involved, which currently remains lacking, will be useful in determining the etiology and treatment of obesity and other conditions resulting from prolonged energy imbalance. Here, we show that a mathematical model of the macronutrient flux balances can capture the long-term dynamics of human weight change; all previous models are special cases of this model. We show that the generic dynamic behavior of body composition for a clamped diet can be divided into two classes. In the first class, the body composition and mass are determined uniquely. In the second class, the body composition can exist at an infinite number of possible states. Surprisingly, perturbations of dietary energy intake or energy expenditure can give identical responses in both model classes, and existing data are insufficient to distinguish between these two possibilities. Nevertheless, this distinction has important implications for the efficacy of clinical interventions that alter body composition and mass.     

Use of balance methods for assessment of short-term changes in body composition

Balance methods reveal changes in body energy, nitrogen, macro‐ and micronutrients as well as fluid in response to different feeding regimens. Under metabolic ward conditions, where physical activity is restricted and activity and food intake are controlled, the errors of estimates of energy intake, energy expenditure, and energy losses are about 2, 4, and 2%, respectively. Balance techniques can be used to validate techniques of in vivo body composition analysis (BCA). This is necessary since immediate and transient changes in body composition in response to a change in diet adversely affect the validity of techniques by violating the assumptions underlying standard methods (i.e., a constant composition or hydration of lean mass). Using two compartment reference methods, like densitometry, dual X‐ray absorptiometry (DXA) or deuterium dilution, changes in fat mass with caloric restriction and overfeeding can be measured with a minimal detectable change (MDC) of 1.0–2.0 kg. However, when compared against balance data, the validity of these techniques to measure short‐term changes in body composition is poor. The noninvasive and rapid new quantitative magnetic resonance (QMR) technique has a high precision with a MDC of 0.18 kg of fat mass. The validity of QMR to assess short‐term changes in fat mass is challenged by comparison to balance data. Today, techniques used for in vivo BCA should be related to steady state conditions only, while in the nonsteady state, the use of balance methods is recommended to assess short‐term changes in body composition.     

Relationship between anthropometric measures and body composition among Muslim females of West Bengal, India

The human body composition is assessed to determine percent body fat (PBF), fat mass (FM), and lean body mass or fat free mass (FFM). The topological distribution of body fat has been the subject of many studies in the world and India. To the best of our knowledge the present paper is the first report on the body composition in terms of PBF and FM, and their relationship with anthropometric measures in Muslim females in India. The present study examines anthropometric measurements and their relationship with the body composition among Muslim females of West Bengal, India. A cross-sectional study of 100 female, Muslim students of Howrah and Kolkata was undertaken to compare the relationships of biceps and triceps skinfold, waist, hip and upper arm circumference, waist hip ratio and conicity index with their body composition variables (PBF and FM). All anthropometric measures displayed significant (p < 0.05) correlation with body composition measures. The triceps skinfold, however, demonstrated a significant correlation with PBF (r = 0.90) and FM (r = 0.93). The greatest amount of variation of PBF (81.3 %) and FM (89.2 %) was explained by the triceps skinfold. In addition, a considerable amount of variation of PBF (72.8 %) and FM (86.0 %) was explained by the mid upper arm circumference. In conclusion, the present study displays a tendency of regional adiposity in the upper arm, triceps skinfold and mid upper arm circumference are much more strongly associated with body fat.     

Non-invasive measure of body composition of snakes using dual-energy X-ray absorptiometry

Non-invasive techniques to measure body composition are critical for longitudinal studies of energetics and life histories and for investigating the link between body condition and physiology. Previous attempts to determine, non-invasively, the body composition of snakes have proven problematic. Therefore, we explored whether dual-energy X-ray absorptiometry (DXA) could be used to determine the body composition of snakes. We analyzed 20 adult diamondback water snakes (Nerodia rhombifer) with a DXA instrument and subsequently quantified their body composition by gravimetric and chemical extraction methods. Body composition components scaled with body mass with mass exponents between 0.88 and 1.53. DXA values for lean tissue mass, fat mass and total-body bone mineral mass were significantly correlated with observed masses of lean tissue, fat and ash from chemical analysis. Using regression models incorporating DXA values we predicted the fat-free tissue mass, lean tissue mass, fat mass, ash mass and total body water content for this sample of water snakes. A cross-validation procedure demonstrated that these models estimated fat-free tissue mass, lean tissue mass, fat mass, ash mass and total-body water content with respective errors of 2.2%, 2.3%, 16.0%, 6.6% and 3.5%. Compared to other non-invasive techniques, include body condition indices, total body electrical conductivity (TOBEC) and cyclopropane absorption, DXA can more easily and accurately be used to determine the body composition of snakes.     

Modeling Body Mass Variation: Incorporating Social Influence into Calculations of Caloric Intake and Energy Expenditure

Variations in individual body mass and composition have long been a key focus in the health sciences, particularly now that overweight and obesity are considered as public health problems. We study a mathematical model that describes body mass variations which are determined by the energy balance between caloric intake and total energy expenditure. To calculate the change in caloric intake and energy expenditure over time, we proposed a relationship for each of these quantities, and we used measured values that are reported in the literature for the initial conditions. To account for small variations in the daily energy balance of an individual, we include social interactions as the multiplication of two terms: social proximity and social influence. We observe that social interactions have a considerable effect when the body mass of an individual is quite constant and social interactions take random values. However, when an individual''s mass value changes (either increases or decreases), social interactions do not have a notable effect. In our simulation, we tested two different models that describe the body mass composition, and it resulted that one fits better the data.     

USE OF BIOELECTRICAL IMPEDANCE ANALYSIS TO ASSESS BODY COMPOSITION OF SEALS

Abstract: Bioelectrical impedance analysis (BIA) measures resistance and reactance of a current as it passes through an organism. The validity of using BIA as a tool to measure body water content, and hence body composition and condition, was tested on harp and ringed seals. The resistance and reactance readings from BIA were compared to estimates of total body water (TBW) determined via tritiated water dilution. The relationship between resistance and TBW (% of body mass) was linear after logarithmic transformation and the two variables were highly correlated. We describe the electrode configuration and placements which provide reliable results in these seals. Our findings indicate that BIA has considerable potential as an inexpensive, rapid, and reliable technique for estimating body composition of phocid seals.     

Anthropometric variables accurately predict dual energy x-ray absorptiometric-derived body composition and can be used to screen for diabetes

The current world-wide epidemic of obesity has stimulated interest in developing simple screening methods to identify individuals with undiagnosed diabetes mellitus type 2 (DM2) or metabolic syndrome (MS). Prior work utilizing body composition obtained by sophisticated technology has shown that the ratio of abdominal fat to total fat is a good predictor for DM2 or MS. The goals of this study were to determine how well simple anthropometric variables predict the fat mass distribution as determined by dual energy x-ray absorptometry (DXA), and whether these are useful to screen for DM2 or MS within a population. To accomplish this, the body composition of 341 females spanning a wide range of body mass indices and with a 23% prevalence of DM2 and MS was determined using DXA. Stepwise linear regression models incorporating age, weight, height, waistline, and hipline predicted DXA body composition (i.e., fat mass, trunk fat, fat free mass, and total mass) with good accuracy. Using body composition as independent variables, nominal logistic regression was then performed to estimate the probability of DM2. The results show good discrimination with the receiver operating characteristic (ROC) having an area under the curve (AUC) of 0.78. The anthropometrically-derived body composition equations derived from the full DXA study group were then applied to a group of 1153 female patients selected from a general endocrinology practice. Similar to the smaller study group, the ROC from logistical regression using body composition had an AUC of 0.81 for the detection of DM2. These results are superior to screening based on questionnaires and compare favorably with published data derived from invasive testing, e.g., hemoglobin A1c. This anthropometric approach offers promise for the development of simple, inexpensive, non-invasive screening to identify individuals with metabolic dysfunction within large populations.     

Evaluation of a non-destructive method for determining egg composition using total body electrical conductivity (TOBEC) measurements

It is widely assumed that there is a positive relationship between egg quality (or egg size) and offspring fitness. However, obtaining unequivocal data in support of this hypothesis has been hampered by the lack of any method for non-destructive determination of egg composition, preventing a direct analysis of egg quality and subsequent chick growth and survival in the same egg(s). In this paper, we describe the application of a rapid, non-destructive technique using measurement of total body electrical conductivity (TOBEC) for determination of egg composition in intact eggs. The TOBEC index was positively and highly correlated with egg lean mass and with the mass of some egg components (albumen and water content). Values for predicted lean mass, based on the regression equation for lean mass against TOBEC index, were within ±6% of actual lean mass. Egg lipid mass was most accurately predicted (±15%) using a multiple regression model, with fresh egg mass and TOBEC index included as independent variables. Egg temperature, and the position of the egg in the sampling chamber, markedly affected the TOBEC index obtained.     

Dynamics of the body liquids and composition in long-duration space flight (Bioimpedance Analysis)

Bioimpedance measurement was used to study dynamics of human hydration status and body composition on board the International space station (ISS). At different stages of 100- to 200-day flights of 12 cosmonauts, the volume of their body liquid was reduced: the overall, intra-, and extracellular volumes became on average 5.2 to 10.4% less per group as compared to the baseline level. The in-flight changes in the body composition of the cosmonauts were also consistent: while the lean mass loss determined by impedance measurement was insignificant (on average, from 1.9 to 4.0%), the gain of the fatty mass ranged from 4.6 to 8.2% during the first three months of the flight. Thus, hydration of a human body decreased during the long-term space flight, which was accompanied by reduction of the muscular mass and the gain in fatty mass.     

Relations among measures of body composition, age, and sex in the common marmoset monkey (Callithrix jacchus)

Few studies of body composition have been done in New World primates. In the study reported here, four methods of assessing body composition (body weight, anthropometry, labeled-water dilution, and total body electroconductivity) were compared in 20 marmosets, aged 0.96 to 7.97 years. Males and females did not differ in any measure (P > 0.05). Body weight ranged from 272 to 466 g, and body fat estimates varied from 1.6 to 19.5%. Strong positive correlations were observed between total body water and total body electroconductivity (R2 = 0.77), body weight and fat-free mass (males R2 = 0.95; females R2 = 0.91), and body weight and fat mass (males R2 = 0.86; females R2 = 0.85; P < 0.01). Male and female slopes were equivalent (P > 0.05) for the regressions of fat and fat-free mass against body weight. Positive correlations also were observed between girth measures and fat-free mass (R2 = 0.48 to 0.78) and fat mass (R2 = 0.60 to 0.74; P < 0.01). A good second- order polynomial relationship was observed between age and fat-free mass for the combined sample (R2 = 0.64). Results indicated that: subjects were lean; there was no sexual dimorphism relative to measures; body weight provided a reliable estimate of fat and fat-free mass; and within-subject body weight changes reflected a similar relationship between body weight and fat-free mass as did that across subjects.     

New insights into body composition assessment in obese women.

During treatment of patients with non-insulin-dependent diabetes mellitus, there may be marked body weight loss. Therefore, body composition should be monitored to check for a decrease in fat mass alone, without an excessive decrease of both fat-free mass and total body water. Accordingly, it is useful to monitor the hydration of these patients. One method that allows us to check the status of body hydration is the multifrequency bioelectric impedance analysis (MFBIA). It makes use of formulas that estimate total body water on the basis of the concept that the human body may be approximated to a cylinder of length equal to body height. In normal subjects body water estimates are sufficiently accurate, but in obese subjects the true hydration status may be overestimated. In this report, we describe the accuracy of mathematical models previously described in the literature, and correct for the overestimation of total body water in obese subjects by means of a new equation based on a new model. The coefficients for each model have been recalculated by the weighing of our sample in order to test the accuracy of estimates obtained with the equations. This new model includes both body volume and two impedances at appropriate frequencies useful for identifying two terms strictly related to extra- and intra-cellular water. The new formulas do not include body weight, but they include the body volume, a parameter more closely related to the biophysical reference model. Fifty-five overweight females, body mass index ranging from 26.8 to 50.2 kg/m2, were enrolled in the study. The proposed equations, taking advantage of two impedance values at appropriate frequencies, better predict total body water in obese women. This was particularly evident when the results obtained with the multifrequency bioelectric impedance analysis and deuterium isotopic oxide dilution method were compared. Although this last method is considered the "gold standard," it is not suitable for use in routine clinical practice. In conclusion, evaluation of total body composition by means of bioelectric impedance analysis might be included in programs for the prevention of non-insulin-dependent diabetes and for monitoring weight loss during overt pathology.     

Influences of landscape composition on hunter-harvested mallard body mass and condition in eastern Arkansas

Waterfowl with more body mass and a greater body condition during the non-breeding season are thought to be more likely to survive and have increased productivity during the following breeding season. Body mass and body condition in waterfowl should reflect the resources available to them locally. We analyzed the relationship of landscape composition on mallard (Anas platyrhynchos) body mass and body condition (mass-wing length index) among age and sex groups. We calculated these variables from hunter-harvested mallards during the 2019–2020 and 2020–2021 duck hunting seasons in the Lower Mississippi Alluvial Valley of Arkansas, USA. We used linear mixed-effects models to analyze changes in body mass and body condition with changes in the percent landscape composition of water cover, woody wetlands, herbaceous wetlands, rice, soybeans, and disturbance. We found that body mass and condition of harvested mallards were positively associated with greater proportions of water cover and woody wetlands but negatively associated with greater proportions of herbaceous wetlands and human disturbance from human infrastructure. Management actions focused on providing flooded and woody wetland areas on the landscape that allow waterfowl to access food resources, while decreasing the disturbance around wetlands in the form of road density and human infrastructure, should increase body mass and body condition in mallards spending the non-breeding season in the Lower Mississippi Alluvial Valley.     

Composition of the body mass overshoot in European barn owl nestlings (Tyto alba ): insurance against scarcity of energy or water?

European barn owl chicks (Tyto alba) show a body mass overshoot prior to fledging that has been predicted to serve as an energy reservoir during periods of stochastic food availability. However, the composition of the mass overshoot has heretofore not been directly examined in nestlings of this or any other species displaying a body mass overshoot during growth (e.g., raptors and seabirds). To experimentally determine whether the overshoot in body mass in juvenile European barn owls (Tyto alba) may act as an energy reservoir, we compared the body composition of owl chicks raised on an ad libitum diet to those fed a restricted diet designed to eliminate the overshoot. Chicks raised on the two diets were also compared for differences in maturation of diverse functions (e.g., locomotion) and tissues (e.g., skeletal development). Contrary to expectations, our results on body composition in juvenile barn owls indicate that the mass overshoot prior to fledging is primarily comprised of an increased water compartment. Thus, we suggest that the mass overshoot in owls (and possibly in other species) does not serve as an energy reservoir but, rather, may function as an insurance against dehydration when hot in-nest conditions force chicks to rely on evaporative cooling: temperatures in barn owl nests can reach up to 43 degrees C. We found no significant differences in maturation indexes between diet treatments at the time of fledging.     

Muscle mass scaling in primates: an energetic and ecological perspective

Body composition is known to vary dramatically among mammals, even in closely related species, yet this issue has never been systematically investigated. Here, we examine differences in muscle mass scaling among mammals, and explore how primate body composition compares to that of nonprimate mammals. We use a literature-based sample of eutherian and metatherian mammals, and combine this with new dissection-based data on muscularity in a variety of strepsirrhine primates and the haplorhine, Tarsius syrichta. Our results indicate an isometric scaling relationship between total muscle mass and total body mass across mammals. However, we documented substantial variation in muscularity in mammals (21-61% of total body mass), which can be seen both within and between taxonomic groups. We also found that primates are under-muscled when compared to other mammals. This difference in body composition may in part reflect the functional consequences of arboreality, as arboreal species have significantly lower levels of muscularity than terrestrial species.     

A standardized assessment of forest mammal communities reveals consistent functional composition and vulnerability across the tropics

The understanding of global diversity patterns has benefitted from a focus on functional traits and how they relate to variation in environmental conditions among assemblages. Distant communities in similar environments often share characteristics, and for tropical forest mammals, this functional trait convergence has been demonstrated at coarse scales (110–200 km resolution), but less is known about how these patterns manifest at fine scales, where local processes (e.g. habitat features and anthropogenic activities) and biotic interactions occur. Here, we used standardized camera trapping data and a novel analytical method that accounts for imperfect detection to assess how the functional composition of terrestrial mammal communities for two traits – trophic guild and body mass – varies across 16 protected areas in tropical forests and three continents, in relation to the extent of protected habitat and anthropogenic pressures. We found that despite their taxonomic differences, communities generally have a consistent trophic guild composition, and respond similarly to these factors. Insectivores were found to be sensitive to the size of protected habitat and surrounding human population density. Body mass distribution varied little among communities both in terms of central tendency and spread, and interestingly, community average body mass declined with proximity to human settlements. Results indicate predicted trait convergence among assemblages at the coarse scale reflects consistent functional composition among communities at the local scale, suggesting that broadly similar habitats and selective pressures shaped communities with similar trophic strategies and responses to drivers of change. These similarities provide a foundation for assessing assemblages under anthropogenic threats and sharing conservation measures.