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PubMed1993

A five-compartment model of body composition of healthy subjects assessed using in vivo neutron activation analysis.

A body composition study of 31 healthy subjects covering a wide range of age (23.5-72.0 years) and weight (44.5-104.2 kg) has been undertaken. Subjects were assessed by in vivo neutron activation and tritiated water analysis and values of total body nitrogen, hydrogen and fat obtained by utilization of a five-compartment model of body composition comprising protein, water, fat, minerals and glycogen. The protein (as 6.25 x nitrogen) and water compartments were measured but the smaller compartments of minerals and glycogen were calculated as fixed fractions of the fat-free mass estimated from the water space. Fat was calculated as the body mass less the sum of the four other compartments. Mean values (+/- SEM), expressed as a percentage of body mass, for nitrogen, hydrogen and fat were 2.56 (+/- 0.07)%, 10.07 (+/- 0.04)%, and 21.9 (+/- 1.7)% respectively for men and 2.14 (+/- 0.07)%, 10.40 (+/- 0.04)%, and 35.5 (+/- 1.7)% respectively for women. The accuracy of the nitrogen measurements was evaluated by comparison with calculated values from two prediction equations; correlation coefficients, the mean bias (estimated from the mean differences between the measured and predicted nitrogen), the confidence interval for the bias, and limits of agreement were calculated. The correlation coefficients were high (r > 0.93) and the mean bias indicative of agreement. The ratio of nitrogen to the fat-free mass (derived from the body composition model) was also calculated and mean values (+/- SEM) of 32.7 (+/- 0.4) and 33.1 (+/- 0.4) g/kg for men and women, respectively were obtained. The hydration of the fat-free mass was determined to be 0.725 (+/- 0.002) and 0.722 (+/- 0.002) kg/kg for men and women respectively. The accuracy of the body fat estimate was evaluated by comparison with skinfold-thickness-derived values and computation from tritiated water space. The ratio of the body composition model to skinfold-thickness-derived fat was significantly (P < 0.005) greater than unity. The mean bias between the body composition model and tritiated-water-derived fat was -0.6 percentage points of fat (95% confidence interval from -0.3 to -0.9 percentage points of fat). Finally a prediction equation (r2 = 0.908, SEE = 108 g) for body nitrogen in healthy subjects based on weight, age and sex was calculated.

Adipose Tissue↗

PubMed2000

Measurements of body composition by dual-energy X-ray absorptiometry improve prediction of energy expenditure.

The prediction of energy expenditure by dual-energy X-ray absorptiometry (DXA) and bioimpedance analysis (BIA) was assessed in 35 healthy individuals of both sexes, with a mean body mass index (BMI) of 23.8 kg/m2 (range 18-33.8), and mean age of 30 years (22-40). Energy expenditure (EE) was measured under standard conditions in a respiration chamber, the total and regional body composition by DXA, and total body composition by BIA. When body composition was measured by BIA, 88.5% of the variation in 24-h EE was explained by lean body mass (LBM); this figure was increased by DXA, where total lean tissue mass (LTM) and total fat tissue mass (FTM) could account for 91.5% of the variation. Also, the prediction of resting energy expenditure (REE) was improved by DXA, from 88.1% to 89.8% (LBM vs. LTM, FTM). Measurements of regional body composition showed that trunk LTM was significantly superior as a predictor, especially of REE and sleeping EE (EE sleep), compared to the peripheral LTM; thus, the predictions of REE were 83% vs. 87% (peripheral vs. trunk), respectively; and the predictions of EE sleep were 83% vs. 89% (peripheral vs. trunk), respectively. Therefore, body composition measurements by DXA improved the prediction of EE. Trunk LTM was a superior predictor, especially of REE and EE sleep, compared to peripheral LTM. In conclusion, the present results suggest that measuring total and regional body composition by DXA can somewhat improve the prediction of EE.

Absorptiometry, Photon↗

PubMed2005

Body composition, dehydroepiandrosterone sulfate and leptin concentrations in girls approaching menarche.

UNLABELLED: There is strong evidence that the initiation of adrenarche and gonadarche during puberty in girls depends on body mass in general and body fat in particular. The aim of this study was to analyze changes in body composition, i.e. body fat (BF), fat percentage (BF%), and lean tissue mass (LM) in girls during pre-menarcheal stages of development, including the earliest stage lacking clinical manifestations of changes in primary, secondary, and tertiary sexual characteristics. Puberty was assessed according to clinical and ultrasonographic staging of sex features developed by us. Concentrations of leptin and DHEA-S were compared and related to changes in body composition. SUBJECTS AND METHODS: The study was carried out on 65 healthy girls aged 8 years and older who were followed every 3 months over a 5-year period. Age, height, weight, and BMI were recorded. Body composition (BF, BF%, LM) was determined with an infrared method. Tertiary sexual features were staged according to Tanner. Vaginal secretion was assessed according to Peter et al. Transabdominal ultrasound of the uterus and ovaries was performed with the bladder unvoided. Groups were formed according to developmental stage: E0A = pre-estrogenization (no ultrasonographic or clinical evidence of estrogenization); E0B pre-estrogenization with 'luminosity' of mucus in cervical canal; E1 = onset of estrogenization; E = full estrogenization; M = menarche +/- 3 months. Concentrations of DHEA-S and leptin were determined by radioimmunoassay. RESULTS: BF in prepubertal girls averaged 16%. At menarche, BF was 23.9%. Body weight at menarche was 50.6 kg and the LM/BF ratio was 3.0. High leptin concentrations were found in E0B and M groups. Leptin concentrations were lowest during full estrogenization (E). Positive correlations of leptin with BF and LM were found in girls during developmental stages preceding menarche. Mean concentration of DHEA-S started at 1,091.6 microg/l during E0A stage, dropped significantly on passing to E0B (p <0.05), and increased by menarche. DHEA-S levels were found to correlate with BF, LM, and leptin in E0A, E0B, and E1 groups. Correlation coefficients were highest (DHEA-S/BF r = 0.61; DHEA-S/LM r = 0.54; DHEA-S/LEP r = 0.57) in the E0A group, i.e. about 5 months before the appearance of 'luminosity' of cervical mucus, considered to be the first ultrasonographic sign of puberty. Apparently, leptin stimulates somatic maturation during this stage of gonadarche which terminates with menarche. The action of DHEA-S is exerted during the early stages of female puberty.

Adolescent↗

PubMed2003

Body composition in Division I football players.

This study assessed body composition of Division I football players (n = 69) and compared the findings with previously reported data to ascertain whether the increase in player total body mass that has been observed over the past 10 years has been accompanied by an increase in body fat. Body composition was determined by hydrostatic weighing and the measurement of skinfold thicknesses. Total body mass, skinfold thicknesses, and body fat were greater in the current players than in players in studies conducted in the early 1980s and early 1990s. Body fat varied significantly across playing position, with the defensive backs, offensive backs, and receivers being the leanest and the offensive linemen and tight ends the most fat. There was no significant relationship between body composition and playing year or scholarship status, nor were any differences observed between ethnic groups. Of important clinical relevance was the finding that the linemen (offensive, defensive) and tight ends were on average greater than 25% body fat, the borderline for obesity in this age group. Much of this fat was deposited in the abdominal region, a significant finding when one considers the high correlation between abdominal obesity and ischemic heart disease and stroke. The current findings suggest that more attention needs to be given to the nature of the increase in body mass being achieved by today's football player to minimize long-term negative health consequences, and the findings reemphasize the need identified in earlier studies of the importance of detraining programs for these athletes.

Adolescent↗

PubMed1986

Applicability of body composition techniques and constants for children and youths.

This review has focused on the chemical immaturity of children and the implications for body composition estimates. Prepubescent and pubescent children deviate considerably in fat-free body composition from the adult reference male, and this has lead investigators to overestimate body fatness in this population using conventional body composition formulas. The use of multicomponent approaches to body composition to obtain more accurate estimates of body fatness in children has provided new information on the body composition of this population. Sex- and age-specific constants, to replace those derived from the reference male, are suggested for further testing and verification as well as for use in the clinical setting. The chemical immaturity in children has its greatest effect on estimating the extent of obesity in children 6 to 11 years of age and in estimating body fatness in the lean, athletic, prepubescent population. Previous estimates of the growth rate of fat and fat-free body are also affected by chemical immaturity. Further research is needed to study the impact of physical activity and inactivity on the composition of the fat-free body during growth, to develop constants for more accurate estimates of fatness in physically active samples of all ages and to validate the constants presented in the less active populations. Future research with multicomponent body composition systems in all populations of children and youth is essential for progress in this area. Results will have an important contribution to the estimation of childhood obesity, prediction of minimal weight in the athletic population and estimates of growth rate of fat and fat-free body mass. The development of body composition methodologies which more accurately measure the growth of muscle and bone as well as fat is a major challenge ahead.

Adipose Tissue↗

PubMed1995

Human body composition and the epidemiology of chronic disease.

Obesity and body fat distribution (FD) are established risk factors for chronic diseases. The body mass index (BMI) and the waist/hip circumference ratio (WHR) are used conventionally as indices of obesity and FD in epidemiological studies. Although some general limitations of these indices are recognized, others that affect their use in relative risks for disease are not well recognized. These include effects of sex, ethnicity, and especially age on the relationships between these indices and body composition, which can result in substantial misclassification of obesity and FD. There is considerable variability in body composition for any BMI, and some individuals with low BMIs have as much fat as those with high BMIs. This results in poor sensitivity for classifying levels of body fatness (e.g., too many "false negatives," or overweight individuals classified as not overweight), and relative risks are attenuated across all categories of BMI. A more serious problem, however, is that at different ages the same levels of BMI correspond to different amounts of fat and fat-free mass. Data from the Rosetta Study and the New Mexico Aging Process Study show that older adults have, on average, more fat than younger adults at any BMI, due to the loss of muscle mass with age. As a result, the sensitivity of BMI cutpoints with respect to body fatness decreases with age, and the use of a fixed cutpoint for all ages results in "differential misclassification bias." Taken together, these issues suggest that the increases with age in the prevalences of overweight and obesity, and in the risks for chronic diseases, may be mis-estimated using BMI. Similar issues may affect the use of WHR for estimating prevalences and associated risks of FD. New field methods for estimating body composition are available that can be applied in large, epidemiologic follow-up studies of chronic diseases. These methods will allow epidemiologists to consider, for example, whether it is increased fat, or the replacement of fat-free mass with fat, with age that is associated with risk for chronic disease.

Adipose Tissue↗

PubMed1996

Techniques used in the measurement of body composition: an overview with emphasis on bioelectrical impedance analysis.

The study of human body composition is now a distinct research area consisting of three interconnected parts: the five-level model and associated rules that govern the relations between components, body-composition methodology, and biological factors that influence body composition. In this overview we summarize fundamental concepts that relate to the five-level model and body-composition methods. We show how these concepts can be used to outline the essential features needed to critically evaluate the bioelectrical impedance analysis method. Body-composition research is a rapidly expanding area and in-depth systematic evaluation of new methods is a vital aspect of the field's growth.

Body Composition↗

PubMed1999

Three year follow-up of body composition changes in pre-menopausal women with systemic lupus erythematosus.

OBJECTIVES: To measure the change in body composition in a pre-menopausal female systemic lupus erythematosus (SLE) population over 3 yr, and to identify predictors of change in body composition including the effects of disease-, corticosteroid (CS)- and patient-related variables. METHODS: All 55 pre-menopausal females with SLE who participated in a cross-sectional study of body composition in 1994 were invited to undergo interview, examination, medical record review, and body composition assessment by dual-energy X-ray absorptiometry (DXA). RESULTS: Twenty-eight subjects participated with a mean (S.E.M.) age of 34.4 (1.6) yr, duration of SLE of 6.8 (0.8) yr and mean (range) time to follow-up of 3.2 (2.9-3.4) yr. Seventeen subjects were exposed to CS during the study period with a mean (range) daily dose of prednisolone of 12.0 (2.8-22.9) mg. There was a significant increase in body mass index (BMI) (24.53+/-0.83 vs 25.37+/-1.04, P = 0.03) and fat-free mass (41.04+/-0.83 vs 41.53+/-0.92, P = 0.05) over the 3 yr period. Univariate analysis revealed that change in fat-free mass was significantly associated with change in total body bone mineral density (BMD) (P = 0.03). Stepwise multiple linear regression analysis revealed a significant independent association of disease activity with increases in both BMI (r2 = 0.41, P = 0.006) and fat mass (r2 = 0.39, P = 0.007), and of exercise and Modified Health Assessment Questionnaire with an increase in fat-free mass (r2 = 0.51, P = 0.007). Age at SLE diagnosis and smoking were significant independent predictors for loss of total body BMD, while CS duration was predictive of an increase in total body BMD (r2 = 0.80, P < 0.0001). CONCLUSION: In this SLE population, disease activity was predictive of deleterious changes in body composition, including increases in BMI and fat mass. Patient-related variables were also important predictors of body composition change with exercise independently predicting an increase in fat-free mass, and smoking predictive of loss of total body BMD. In contrast, CS-related variables were not found to have harmful effects on body composition. Change in fat-free mass, and not fat mass, was predictive of change in total body BMD.

Absorptiometry, Photon↗

PubMed2003

Body composition during normal pregnancy: reference ranges.

Maternal body composition undergoes a deep adaptative change during the course of pregnancy. Fat mass, fat-free mass, and total body water (TBW) increase in different ways and their effects on pregnancy outcome represent a field of major interest in perinatal medicine. The aim of this study was to evaluate the changes in maternal body composition [maternal weight, TBW, intracellular water (ICW) and extracellular water (ECW)] during healthy pregnancy by using bioimpedance analysis (BIA). A total of 170 healthy pregnant women, aged 22-44 years, volunteered to participate in our study. The BIA measurements were carried out with a Tefal BIA scale determining resistance and reactance. Lukaski's multiple-regression equation was used to estimate TBW and ICW and ECW were computed using the prediction formula of Segal. The evaluations were performed at 10-38 weeks' gestation, every 3-4 weeks, and hematocrit was determined at every time interval. Analysis of variance and multiple comparisons of Bonferroni were performed to compare variables among the different study intervals. Second-order polynomial interpolation was used to obtain percentile values for each bioimpedance parameter. Percentile bioimpedance values of the healthy population are provided at each study time, by showing the mean value and the 5th, 25th, 75th, 95th percentiles. Moreover, normal reference ranges for TBW are provided for each gestational age, in relation to maternal weight gain. Reactance, TBW, and ICW enhance slightly during the course of gestation. Tetrapolar BIA could be an easy and practical tool for evaluating changes of maternal body components during pregnancy. It could also provide indirect proof of the normal hemodilution occurring in normal pregnancies. Moreover, fat mass deposition, and not only fluid retention, seems to be responsible for the mother's gestational weight gain, since reactance is an indirect parameter in estimating fat mass amount.

Adipose Tissue↗

PubMed1996

[Canonical correlation of body composition and pulmonary function in children aged eight to twelve].

Canonical correlation of body composition and pulmonary ventilation function in school boys and girls aged 8 to 12 and normally developed was analyzed. Skinfolds of triceps and subscapular angle were measured, and body composition was estimated as body fat percentage (BF%), body fat (BF) and lean body mass (LBM). Ventilation function was measured. Results indicated that correlation between body composition and ventilation function mainly attributed to a positive correlation between LBM and vital capacity (VC) and a negative correlation between BF% and a ratio of expiratory reserve volume (ERV) to VC. It suggests effects of body composition on ventilation function mainly attributed to LBM and BF%.

Body Composition↗

PubMed2004

Validation of a new pediatric air-displacement plethysmograph for assessing body composition in infants.

BACKGROUND: The accurate measurement of body composition is useful in assessments of infant growth and nutritional status. OBJECTIVE: This study evaluated the reliability and accuracy of a new air-displacement plethysmography (ADP) system for body-composition assessment in infants. DESIGN: Between- and within-day reliability was assessed by comparing the percentage body fat (%BF) obtained on consecutive days and on the same day, respectively, in 36 full-term infants. Accuracy was assessed by comparing %BF measured with the use of ADP and %BF measured with the use of deuterium (2H2O) dilution in 53 infants. RESULTS: There were no significant differences in %BF between days (-0.50 +/- 1.21%BF) or within days (0.16 +/- 1.44%BF). Mean between- and within-day test-retest SDs of 0.69 and 0.72%BF, respectively, indicated excellent reliability. The %BF measurements obtained by using ADP were not significantly influenced by infant behavioral state. Mean %BF obtained by using ADP (20.32%BF) did not differ significantly from that obtained by using 2H2O dilution (20.39%BF), and the regression line [%BF(2H2O) = 0.851%BF (ADP) + 3.094] gave a high R2 (0.76) and a low SEE (3.26). The 95% limits of agreement between ADP and 2H2O (-6.84%BF, 6.71%BF) were narrower than those reported for other body-composition techniques used in infants. Individual differences between the 2 methods were not a function of body mass or fatness. CONCLUSION: ADP is a reliable and accurate instrument for determining %BF in infants, and it has the potential for use in both research and clinical settings.

Body Composition↗

PubMed1998

Body composition in systemic lupus erythematosus.

The objectives were to determine the body composition, and the effects of disease and corticosteroid therapy on body composition, in a population of female patients with systemic lupus erythematosus (SLE). All female SLE patients managed through a single centre were invited to participate in a cross-sectional study of body composition. Data were collected by standardized interview and examination, and review of medical records. Body composition was assessed by dual-energy X-ray absorptiometry (DXA). Eighty-two subjects were evaluated, 30 of whom were post-menopausal. Univariate linear regression analysis revealed a significant association of reduced fat-free mass with SLE severity [as measured by the Systemic Lupus International Collaborative Clinics (SLICC)] (P = 0.020), a history of corticosteroid exposure (P = 0.043) and age (P = 0.048). Reduced total body bone mineral density (BMD) was also significantly associated with SLICC (P < 0.001) and corticosteroid exposure (P = 0.017), and with age (P < 0.001), post-menopausal status (P = 0.003) and the duration of menopause (P < 0.001). Stepwise multiple linear regression analysis revealed a significant association between fat-free mass and total body, lumbar spine and femoral neck BMD (P = 0.007, P = 0.025, P = 0.003, respectively). Fat mass was significantly associated only with lumbar spine BMD (P = 0.008). In this SLE population, disease severity and corticosteroid exposure were independently associated with a negative effect both on total body BMD and on fat-free mass. Fat-free mass was a significant predictor of lumbar spine, femoral neck and total body BMD.

Absorptiometry, Photon↗

PubMed1989

The effect of a competitive season on the body composition of university female athletes.

Fifty-six NCAA Division I female athletes (age +/- SD = 19.82 +/- 0.59 years) from the swimming (SW), track (TR), volleyball (VB), gymnastics (GYM) and basketball (BB) teams were measured preseason and postseason to determine the effects of a season's training on their body composition. Body density (BD), relative fat (RF), fat-weight (FW), and fat-free weight (FFW) were obtained via hydrostatic weighing. The TR and GYM athletes showed significant increases and the VB players significant decreases in BD and FFW across season, respectively. No significant changes were found for the SW and BB teams. Preseason comparisons showed greater BD for TR than for BB, VB or SW. The GYM and VB had lower BD values than SW. Fat-free weight was higher in BB and VB teams, while TR and SW teams had greater FFW than GM. The BB, VB and SW teams had greater preseason FW than the TR and GYM groups. Postseason comparisons showed greater BD in TR and GYM than in the other three groups. Although FW differences were consistent with preseason data, all groups differed significantly in FFW with BB players having the greatest amount followed by VB, SW, TR and GYM.

Adipose Tissue↗

PubMed1998

Bioelectrical impedance analysis to assess body composition in obese adult women: the effect of ethnicity.

OBJECTIVE: To examine whether the accuracy of bioelectrical impedance analysis (BIA) to estimate body composition in overweight women is affected by the ethnicity of the individuals. DESIGN: Cross-sectional design to compare body composition estimated by BIA to body composition measured by dual energy x-ray absorptiometry (DEXA), which was the reference method. SUBJECTS: One hundred twenty three overweight women participated in this study, of which 43 women were African-American (aged 37.2+/-5.6 y; BMI, 32.3+/-4.9 kg/m2) and 80 were Caucasian (aged 36.1+/-5.7 y; BMI, 31.9+/-3.5 kg/m2). MEASUREMENTS: Body composition was estimated from BIA using both a generalized and an obesity-specific equation. These estimations were compared to body composition measured by DEXA, which was the reference method. RESULTS: The generalized BIA equation underestimated lean body mass (LBM) by 2.6+/-3.1 kg in Caucasian women and 0.4+/-3.2 kg in African-American women, with the difference between the ethnic groups being significant (P < 0.001). The obesity-specific equation underestimated LBM in Caucasians by 0.9+/-3.1 kg and overestimated LBM in African-Americans by 1.2+/-2.8 kg (P < 0.001). An ethnic-specific equation is proposed, and cross-validation of this equation indicates that it provides a reasonable estimate of body composition in overweight women. CONCLUSIONS: The accuracy of BIA to estimate body composition appears to be affected by the ethnicity of the individual. Therefore, an ethnic-specific equation for overweight women is proposed. However, further validation of this prediction model in an ethnically diverse population is necessary.

Absorptiometry, Photon↗

PubMed2000

Resting metabolic rate, body composition, and serum leptin concentrations in a free-living elderly population.

OBJECTIVE: The present study investigated the relationship between serum leptin concentrations and resting metabolic rate (RMR) in a large study group of elderly individuals with special consideration of body composition and body fat distribution as possible confounders. DESIGN AND METHODS: The subjects were 122 women (age: 69+/-6 years, body mass index (BMI): 26.3+/-3.6 kg/m(2)) and 82 men (age: 69+/-5 years, BMI: 26.0+/-2.6 kg/m(2)). RMR was measured by indirect calorimetry and body composition by the bioelectrical impedance method. Serum leptin levels were determined by radioimmunoassay. RESULTS: There was a strong correlation between fat mass (FM) and serum leptin levels in both sexes. An age-related decline in leptin levels adjusted for FM was observed only in the women. After adjustment of RMR for both fat-free mass (FFM) and FM, leptin levels were not associated with RMR. In stepwise multiple regression analysis, FFM was the main predictor of RMR, explaining 35.8% and 47.6% of the variance of RMR in men and women respectively. FM did not explain variance in RMR in men, but accounted for 2.6% of the variance in RMR in women. Waist-hip-ratio and age influenced RMR only in males, explaining 5.7% and 4.0% of the variance in RMR respectively. CONCLUSION: Leptin is not a significant predictor of RMR in the elderly, but body composition and distribution of body fat are significantly associated with RMR.

Age Factors↗

PubMedDate not supplied

Body composition in elderly persons: a critical review of needs and methods.

Significant changes in body composition that have important health related effects are believed to occur in the elderly. Knowledge of these changes is important for diagnoses, prognoses, and treatment of health problems. Many health problems in the elderly could be prevented or alleviated by nutritional modulation, but better understanding of the nature, extent, and underlying physiology of body compositional changes is needed for such interventions to be successful. There are currently few data for body composition in the elderly, especially for those greater than 75 y in age, partly because conventional methods of assessing body composition are difficult to apply for technical and conceptual reasons. As a result, little is known regarding the relationships of body composition to nutritional, functional or health status in non-hospitalized, free-living elderly persons. Knowledge of the "natural history" of body compositional changes and their relationships to other nutritional and health factors could lead to new insights on prevention and treatment, the reduction of morbidity and extension of the quality of life of older persons.

Adult↗

PubMed2003

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.

Absorptiometry, Photon↗

PubMedDate not supplied

Time-dependent variation in weight and body composition in healthy adults.

OBJECTIVES: To define the limits of change in body weight and body composition after different time intervals in healthy, normal adults. METHODS: Prospective and retrospective analyses of paired body composition studies in a total of 326 healthy adults, ages 18 to 97. Measurements included body weight, fat and fat-free mass (FFM) by dual x-ray absorptiometry (DXA) and bioimpedance analysis (BIA), plus body cell mass (BCM) by whole-body counting of 40K and BIA. RESULTS: Time interval between studies was a significant predictor of the differences in paired studies. The 95% confidence intervals for percent difference were lowest for body weight, intermediate for BCM and FFM, and highest for fat, in part because of the differences in sizes of these body compartments. There were significant associations among the changes in body composition by BIA and by criterion methods, suggesting that the observed changes are real. CONCLUSIONS: The normal variation in body weight and body composition increases over time. Time-dependent criteria may increase the sensitivity in diagnosing malnutrition. Interpreting changes in body compartments requires consideration of the size of each compartment.

Absorptiometry, Photon↗