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PubMed2000

Dual-energy X-ray absorptiometry measurements of the body composition of pigs of 90- to 130-kilograms body weight.

We used the pig as an in vivo model for evaluating the effects of extreme body depth on the measurement of body composition by dual-energy X-ray absorptiometry (DXA). One group of 17 pigs weighed an average of 90 kg and had a maximum body depth of approximately 30 cm; another group of 54 pigs weighed 123 kg on average and had a maximum body depth of about 35 centimeters. In the larger pigs, DXA tended to measure a higher percentage of total body fat relative to the chemical analysis than in the smaller pigs. In both groups, but more predominantly in the larger pigs, there were areas in the bone of extreme thickness and/or density that were excluded from the analysis, which caused underestimation of bone mineral content and total tissue mass.

Absorptiometry, Photon↗

PubMed1999

Effect of body composition on oxygen uptake during treadmill exercise: body builders versus weight-matched men.

Oxygen uptake (VO2) during treadmill exercise is directly related to the speed and grade, as well as the participant's body weight. To determine whether body composition also affects VO2 (ml.kg-1.min-1) during exercise, we studied 14 male body builders (M weight = 99 kg, SD = 7; M height = 180 cm, SD = 8; M body fat = 8%, SD = 3; M fat free mass = 91 kg, SD = 7) and 14 weight-matched men (M weight = 99 kg, SD = 9; M height = 179 cm, SD = 5; M body fat = 24%, SD = 5; M fat free mass = 73 kg, SD = 9). Percentage of body fat, t(13) = 8.185, p < .0001, and fat free mass, t(13) = 5.723, p < .0001, were significantly different between groups. VO2 was measured by respiratory gas analysis at rest and during three different submaximal workrates while walking on the treadmill without using the handrails for support. VO2 was significantly greater for the lean, highly muscular men at rest: 5.6 +/- 1 vs. 4.0 +/- 1 ml.kg-1.min-1, F(1, 26) = 21.185, p < .001; Stage 1: 1.7 mph/10%, 18.5 +/- 2 vs. 16.1 +/- 2 ml.kg-1.min-1, F(1, 26) = 6.002, p < .05; Stage 2: 2.5 mph/12%, 26.6 +/- 3 vs. 23.1 +/- 2 ml.kg-1.min-1, F(1, 26) = 7.991, p < .01; and Stage 3:3.4 mph/14%, 39.3 +/- 5 vs. 33.5 +/- 5 ml.kg-1.min-1, F(1, 26) = 7.682, p < .01, body builders versus weight-matched men, respectively. However, net VO2 (i.e., exercise VO2 - rest VO2) was not significantly different between the two groups at any of the matched exercise stages. The findings from this study indicate that VO2 during weight-bearing exercise performed at the same submaximal workrate is higher for male body builders compared to that measured in weight-matched men and that which is predicted by standard equations. These observed differences in exercise VO2 appear to be due to the higher resting VO2 in highly muscular participants.

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PubMed1990

Alterations in body composition after gastroplasty for morbid obesity.

Body compositional changes during rapid weight loss and after weight stabilization were prospectively studied in morbidly obese patients undergoing gastroplasty operations. Body composition was studied preoperatively and 6 and 24 months postoperatively in 23 patients by use of a total body counter (40K) and an isotope dilution technique. The mean fat mass, cell mass, and intracellular water (ICW) decreased during the first 6 months (p less than 0.001) and remained unchanged at the 24-month test. However, the mean liters of extracellular water (ECW) did not change. Consequently, the ECW/ICW ratio, high in states of malnutrition, rose above postoperative levels. A strong correlation was found between decreases in cell mass and increases in the ECW/ICW ratio.

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PubMed1993

Measurement of body composition of live rats by electromagnetic conductance.

Measurement of body composition in vivo is important in many nutritional studies. One method for estimating body composition is total body electrical conductance (TOBEC). The TOBEC methodology is based on measuring changes of an electromagnetic field that are proportional to lean body mass (LBM). Sprague-Dawley rats (n = 117) ranging in age from 49 to 105 days were measured by TOBEC, and the TOBEC results were compared with direct carcass chemical analyses. The rats ranged in weight from 155 to 500 g. Mean LBM was 92.4% of total body weight (b.wt.), and mean body fat was 7.4% of total b.wt. Mean hydration of LBM was 71.7% and decreased (r = -0.59, p < 0.0001) with age. Using the manufacturer's supplied equation, TOBEC measurement underestimated actual LBM by 12% (p < 0.0001). As a consequence of this error, a new prediction equation was generated using half of the data set, and this equation was cross-validated with the other half of the data set. The mean LBM calculated from the new prediction equation was not different from chemically determined LBM, but the estimated percent body fat of some rats was negative. Thus, TOBEC may be useful in predicting mean LBM of a population, but this indirect method may lack the sensitivity to provide accurate estimates of body composition of an individual.

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PubMed1997

Relationship between physical activity related energy expenditure and body composition: a gender difference.

OBJECTIVE: The doubly labeled water method for the measurement of average daily metabolic rate (ADMR), combined with a measurement of basal metabolic rate (BMR), permits the calculation of energy expenditure for physical activity. Thus, the relation between physical activity and body composition (%body fat) can be determined. METHOD: We analyzed existing data sets with observations on ADMR, BMR, and %body fat including 290 healthy subjects, age 18-49 y, 146 females and 144 males, from 22 different studies. RESULTS: In a regression analysis, age explained 3-7% and 5-20% of the variation in %body fat in females and males, respectively. Adding physical activity to the model raised the explained variation in %body fat in males (partial r = -0.35, P < 0.01). A higher level of physical activity was related to a lower %body fat. In females, there was no relationship between physical activity and body composition (partial r = 0.00, n.s.). CONCLUSION: In males, there is a significant inverse cross-sectional relationship between activity energy expenditure and percent body fat, whereas no such relationship was apparent in females.

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PubMed2002

Body composition: what's new?

PURPOSE OF REVIEW: Body mass index has been shown to be an imprecise measurement of fat-free and fat mass, and provides no information if weight changes occur as a result of a decrease in fat-free mass or an increase in fat mass. RECENT FINDINGS: Non-invasive body composition methods (i.e. bioelectrical impedance analysis, air displacement plethysmography) can now be used to monitor fat-free and fat mass with weight gain and loss, and during aging. This review discusses body composition measurements in terms of ethnic differences, physical activity, and age, and the limitations of bedside techniques in obesity and abnormal hydration status. SUMMARY: An assessment of the fat-free and fat mass provides valuable information about changes in body composition with weight gain or loss and physical activity, and during aging. Non-invasive bedside techniques can now be used to evaluate the nutritional status of healthy and ill individuals.

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PubMed1994

Accuracy and reliability of total body electrical conductivity (TOBEC) for determining body composition of rats in experimental studies.

Total body electrical conductivity (TOBEC) has been promoted as a noninvasive method to estimate body composition in small mammals. Validation of this method has primarily been under normative conditions and has generally been inadequate. This article reports on the reliability and accuracy of TOBEC methodology to assess gradual, physiologically induced changes in body composition in rats under different experimental conditions. Reliability of the index of electrical conductivity (EM number) was assessed by analyzing components of variance. Accuracy was assessed by comparing EM number to actual lean body mass (LBM, from carcass analysis), across different experimental conditions, within a particular experimental condition, and over time for a given set of animals. Reliable measurements were obtained by strictly adhering to a standard protocol. TOBEC was inaccurate across experimental conditions, within experimental conditions, and within a single experimental condition during the course of an experiment. This inaccuracy apparently stemmed from the lack of a direct relationship between EM number and LBM; EM number was more strongly correlated with body weight than with LBM. At the present time, TOBEC cannot be used in place of carcass analysis to accurately predict the body composition of rats during or following the administration of a variety of experimental conditions.

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PubMed1999

Body composition of preterm infants during infancy.

AIMS: To examine body composition in preterm infants. METHODS: Body composition was measured by dual energy x-ray absorptiometry (DEXA) at hospital discharge, term, 12 weeks, and at 6 and 12 months corrected age in 125 infants (birthweight < or = 1750 g, gestational age < or = 34 weeks). RESULTS: Body weight derived by DEXA accurately predicted that determined by conventional scales. In both sexes lean mass (LM), fat mass (FM), %FM, bone area (BA), bone mineral mass (BMM), and bone mineral density (BMD) increased rapidly during the study; significant changes were detectable between discharge and term. At 12 months, LM, BA, and BMM, but not FM, %FM, or BMD were greater in boys than in girls. Corrected for age, LM was less than those of the reference term infant; FM and %FM were similar; BMM was greater. Corrected for weight, LM was similar to those of the reference infant, while the FM and %FM of study infants were slightly greater. CONCLUSIONS: DEXA accurately measures body mass. Body composition in preterm boys and girls differs. Interpretation of DEXA values may depend on whether age or body weight are regarded as the appropriate reference.

Absorptiometry, Photon↗

PubMed1989

Potential use of bioelectrical impedance of the 'whole body' and of body segments for the assessment of body composition: comparison with densitometry and anthropometry.

The value of 'whole body' and segmental impedance measurements, and of simple anthropometric methods for predicting body composition was assessed in 24 normal (14m, 10f) subjects (BMI, 18.3-28.6), using densitometry as the reference method. The contribution of segmental impedance was assessed in a separate group of 24 normal (12m, 12f) subjects (BMI, 19.8-28.8) at two frequencies (1 kHz and 50 kHz). Estimates of specific resistivities of certain individual segments (upper arm, forearm, upper leg, and lower leg) were also made in this group, and compared to those obtained from a group of 7 obese female subjects (BMI, 32.6-56.1). The bias and 95 per cent limits of agreement between densitometrically determined body composition (fat and fat-free mass, and total body water) and the alternative methods were found to vary considerably, depending on the technique and/or equations employed. Estimates of whole body composition based on impedance or resistance measurements were found to be associated with only slightly smaller limits of agreement than those made by anthropometry. The upper limb was found to have the greatest influence on whole body impedance measurements. Indeed, the forearm, which accounts for 1.3 per cent of body weight contributes 25.0 per cent to 'whole body' impedance. The estimated specific resistivities of segments were found to be considerably greater in the obese individuals than in normal female subjects (for example, 75 per cent higher for the upper arm, P less than 0.001). The results suggest that: (a) there may be a systematic, population-related, error in predicting densitometric estimates of body composition with the use of standard equations, which incorporate variables such as weight, height, skinfold thicknesses, and impedance/resistance measurements; (b) in this population, impedance or resistance measurements confer only a small advantage over simple anthropometry for predicting body composition; (c) the impedance of the arm or leg may provide a simple alternative method for assessing the composition of the whole body; and (d) the estimated specific resistivity of individual body segments may be useful for assessing the composition of those segments.

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PubMed1997

Measurement of body composition: applications in hormone research.

Measurements of body composition are fundamental to the diagnosis and management of a number of diseases. However, these measurements must be appropriate and accurate. Accuracy can now be achieved, but at the expense of invasiveness (mainly radiation) and cost. Some methods for measuring body composition, such as bioimpedance analysis, are inexpensive, simple, harmless and infinitely repeatable. The remaining methods fall within a scale of increasing discriminating power and increasing cost/risk/difficulty. In this review, a number of methods of measuring body composition are discussed. Both traditional and new methods are included, which vary in ease of use, invasiveness and cost. The choice of technique depends on the needs of a particular study.

Absorptiometry, Photon↗

PubMedDate not supplied

Relationship of body composition measures and menstrual cycle length.

Menstrual cycle disruption has been observed in women with low body weight due to anorexia nervosa, or to athletics. However, the association of the full range of body composition measures with cyclicity has not been determined. Therefore, the purpose of this study was to determine the strength and direction of association between body composition measures (Quetelet Index, body fat mass, and body lean mass) and menstrual cycle length. Menstrual cycle diaries were distributed to women aged 24-45 in the Michigan Bone Health Study beginning in 1992. A total of 4392 menstrual cycles from 436 women were analysed from the first year of this ongoing study. Body composition measures (Quetelet Index or body mass index (kg/m2), body fat mass and body lean mass (kg) were obtained at annual clinic visits by means of dual-energy X-ray absorptiometry (DEXA). Mixed-model analyses were used to determine the degree of association between menstrual cycle length and body composition measures, controlling for age. There was a significant positive association with cycle length for each body composition measure. The relationship between each body composition measure and cycle length was nonlinear with the longest mean cycle lengths occurring with greater BMI, body fat mass or body lean mass. Longer cycle length was also noted at the lowest levels of BMI and body fat mass. These results may account for the purported later age at menopause for obese women.

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PubMed1994

Accuracy of dual-energy x-ray absorptiometry for body-composition measurements in children.

The accuracy of body-composition measurements by dual-energy x-ray absorptiometry (DXA) was assessed by comparison with total carcass chemical analysis in 16 pigs with a weight range of 5-35 kg. Two software versions for body-composition analyses with the DXA instrument were evaluated. Although both software versions accurately predicted body weight, there were significant differences in the partitioning between bone mineral content (BMC), nonbone lean tissue, and body-fat compartments. All estimates of body composition were highly correlated (r2 > or = 0.98) with the results of the direct chemical reference method. SEEs were 226-271 g for body weight, 387-429 g for fat, 3.5-4.3 kg for fat-free mass, and 35.4-36.5 g for BMC. For bone, both software versions produced BMC values that were approximately 25% below the total carcass ash content. For the absolute mass of body fat, one DXA analysis provided underestimates that averaged 19.5% below the reference chemical method, whereas the alternate software version resulted in over-estimates, averaging 15.5%. Conversely, the average fat-free compartment was initially overestimated by 968 g, then underestimated by 892 g. The impact of these differences in the body-composition analyses by DXA were examined in a group of 18 young boys 4-12 y of age.

Absorptiometry, Photon↗

PubMed1992

Effect of increased production of growth hormone on body composition in mice: transgenic versus control.

The body composition (water, fat, protein and ash) of male and female transgenic mice which had a sheep metallothionein 1a-sheep growth hormone fusion gene and their non-transgenic controls was determined at intervals from birth to 21 days of age (weaning) in 66 mice of each group, and in an additional 64 mice over the period 25 to 98 days of age. Overall 520 mice were analysed. Weaned mice were starved overnight prior to slaughter. Food was available ad libitum. and, after weaning, a zinc sulphate supplement was added to the drinking water to initiate expression of the transgene. Growth and body composition were similar in all groups before weaning. From 39 days of age, transgenic females became progressively heavier than corresponding controls, being 60% heavier at the end of the experiment. They contained less fat, more water and slightly less ash than did controls of the same live weight but similar amounts of protein. When examined on a fat-free basis, they had less protein and ash and more water than corresponding controls. Appropriate linear and quadratic regression equations are presented to describe the above relationships. Growth and body composition were more variable in transgenic males but, on average, similar to controls.

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PubMed1992

Relative validity of different methods to assess body composition in apparently healthy elderly women.

Body composition was assessed by means of densitometry, anthropometry and bioelectrical impedance in 28 healthy, elderly females, aged 67-78 years. Underwater weighing was used as the reference method. Mean body mass index (BMI) was 26.3 +/- 3.4 kg/m2. Body fat percentage from body density was 39.6 +/- 5.6%. The fat-free mass (FFM) from body density was 41.0 +/- 5.4 kg. Mean predicted FFM using different prediction formulas from the literature ranged from 38.8 +/- 4.2 to 46.3 +/- 5.3 kg. The differences between FFM from densitometry and FFM using either prediction equation were highly correlated, thus part of the difference is probably due to an error in the reference method. The different prediction equations revealed rather good relative validity, compared to the densitometric method, with the exception of equations based on skinfold measurements developed in younger reference populations. Age-specific prediction equations based on BMI and bioelectrical impedance measurement may be used to assess body composition in the elderly. Prediction equations using skinfold thickness measurements are less appropriate for this purpose.

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PubMed2001

Relation between body composition, fat distribution, and lung function in elderly men.

BACKGROUND: Body composition changes with age, with increases in fat mass and visceral fat and declines in skeletal muscle mass; lung function also declines with age. Age-related changes in body composition and fat distribution may be associated with the pulmonary impairment observed in the elderly. OBJECTIVE: Our goal was to evaluate the relations between body composition, fat distribution, and lung function in elderly men. DESIGN: We studied 97 men aged 67-78 y with body mass indexes (BMIs; in kg/m2) ranging from 19.8 to 37.1. Body composition was evaluated by using dual-energy X-ray absorptiometry and fat distribution was evaluated by using waist and hip circumferences, waist-to-hip ratio, and sagittal abdominal diameter (SAD). Spirometry was done in all subjects and the distance walked by each subject during a 6-min walking test was evaluated as was leg strength. RESULTS: A significant negative correlation was found between adiposity, fat distribution indexes, forced vital capacity (FVC), and forced expiratory volume in 1 s (FEV1). A positive correlation was found between fat-free mass and FVC. After adjustment for age, height, and weight, SAD still correlated negatively with FVC and FEV1 (r = -0.367 and -0.348, respectively; P < 0.01), whereas percentage body fat and fat mass correlated negatively and fat-free mass correlated positively with FVC (r = -0.313, -0.323, and 0.299, respectively; all P < 0.01). After the sample was subdivided by tertile of fat-free mass adjusted for age and BMI, FVC and FEV1 were significantly lower in the lowest fat-free mass tertile (P < 0.01). Stepwise multiple regression analysis performed with use of lung function variables as the dependent variables and age, height, fat mass, fat-free mass, waist circumference, and SAD as the independent variables showed that 3 variables entered the regression for predicting FVC: height, which entered the regression first; SAD, which entered second; and fat-free mass, which entered third. Only 2 variables entered the regression for predicting FEV1: height, which entered the regression first, and SAD, which entered second. CONCLUSION: Our cross-sectional data show a significant association between body composition, fat distribution, and lung function in elderly men.

Absorptiometry, Photon↗

PubMed2006

Two-component models are of limited value for the assessment of body composition in patients with cirrhosis.

BACKGROUND: Most techniques for measuring body composition are based on 2-component models (2-CMs) and depend on assumptions relating to the constancy of the density (D(FFM)) and hydration fraction (HF(FFM)) of fat-free mass (FFM). OBJECTIVES: The objectives were to determine whether these assumptions are systematically violated in patients with cirrhosis and to assess the validity of the estimates of body composition obtained in these patients by using 2-CM techniques. DESIGN: Body composition was assessed by using a 4-component model (4-CM), which was based on data obtained from densitometry, deuterium dilution, and dual-energy X-ray absorptiometry, in 20 patients with cirrhosis who had no evidence of fluid retention and in 20 pair-matched healthy control subjects. The results were compared with those obtained by using "reference" and "bedside" 2-CM techniques. RESULTS: The mean (+/-SD) D(FFM) was significantly lower in the patients with cirrhosis (1.091 +/- 0.008 compared with 1.100 +/- 0.006 kg/L; P < 0.001); no significant difference in HF(FFM) was observed between the patients and control subjects (74.5 +/- 2.6 compared with 73.5 +/- 2.1), although there was greater variability in the patients. Significant differences were observed in the body-composition variables obtained by using the "reference" 2-CM techniques compared with the 4-CM-the 95% limits of agreement in the patients with cirrhosis exceeded 5% body fat and 3 kg FFM; the corresponding values for the "bedside" 2-CM techniques were 11% body fat and 7.5 kg FFM. CONCLUSIONS: Assumptions relating to the constancy of the D(FFM) and HF(FFM) are violated in patients with cirrhosis. Thus, standard 2-CM techniques provide inaccurate body composition estimates in this patient population.

Absorptiometry, Photon↗

PubMed1985

Influence of body composition on insulin clearance.

The effect of body composition on clearance of infused insulin was studied in 21 young normal weight (relative body weight 107 +/- 2%, of ideal mean +/- SEM) healthy subjects. In each subject, the per cent of body weight made up of muscle and fat tissue (% muscle and % fat) were determined. Clearance of insulin was estimated during infusion of insulin at the rate of 40 mU/m2/min under maintenance of normoglycaemia using the euglycaemic clamp technique. Steady-state plasma insulin levels (92.6 +/- 3.2 mU/litre) correlated negatively with % muscle (r = -0.60, P less than 0.01), and positively with % fat (r = 0.55, P less than 0.01). Clearance of insulin was directly related to % muscle (r = 0.60, P less than 0.01), and inversely related to % fat (r = -0.48, P less than 0.01). Steady-state plasma insulin levels or insulin clearance did not correlate with relative body weight. Multiple linear regression analysis revealed a significant multivariate correlation between the rate of insulin clearance versus % muscle and % fat (r = 0.62, P less than 0.02). The changes in % muscle and % fat could predict 37% of the observed interindividual variance of insulin clearance. These results indicate that insulin clearance depends on body composition and is higher in muscular than in adipose subjects. This difference may reflect either a greater distribution space of insulin in muscular as compared to adipose subjects or an influence of body composition on insulin catabolism.

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PubMed1993

Body composition of patients with Alzheimer's disease.

Low body weight is frequently reported in patients with Alzheimer's disease. We sought to discover why by comparing the body composition of 28 cognitively normal elders and 23 institutionalized individuals with Alzheimer's disease. Body mass index was calculated from standing height and weight. Percentages of lean body mass, body fat, and body water were derived from bioimpedance measurements of resistance and reactance. Skinfold thickness was measured at seven body sites to estimate regional fat distribution. Variables were analyzed by analysis of variance with subjects grouped by cognitive status within gender. Activity level and age were not significant covariates. Both women and men with Alzheimer's disease weighed less than control subjects. Differences in body composition were more pronounced in women with Alzheimer's disease, who had lower body mass index (22.0 +/- 3.0 vs 26.1 +/- 5.1), higher percentage of lean body mass (73.8 +/- 5.1 vs 66.9 +/- 6.5), lower percentage of body fat (26.1 +/- 5.1 vs 33.1 +/- 6.5), and higher percentage of body water (55.8 +/- 5.0 vs 49.3 +/- 6.5) compared with control women. Except for lower body weight, the body composition of men with Alzheimer's disease was not significantly different from that of control men. Patients of both sexes with Alzheimer's disease had less truncal body fat compared with controls, which gave them a youthful body habitus. These differences were not accounted for by age, diet, or activity. Our findings indicate that patients with Alzheimer's disease have lower body weight and may require higher energy intake than cognitively normal elders.

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