PubMed Health⌕ Search

Biomedical subjects

R N Baumgartner

Publications and source records attributed to R N Baumgartner.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1995

Cross-sectional age differences in body composition in persons 60+ years of age.

BACKGROUND: There is little information for age differences in body composition in elderly people > 65 years of age, especially for those > 80 years. As the proportion of people older than 65 years is expected to nearly double during the next few decades, this information is needed. METHODS: Age differences in body composition and anthropometry were examined in 316 men and women aged 60 to 95 years. Multiple components of body composition were quantified using dual energy X-ray absorptiometry and isotope dilution methods, and expressed in molecular and cellular models. Analysis of variance was used to test for differences between age groups 60 to 70, 71 to 80, and > 80 years in each sex. Body composition components were regressed on age, controlling for knee height, fat-free mass, or total body fat. Age-adjusted correlations were calculated with anthropometric variables. RESULTS: Fat-free mass (FFM), body cell mass (BCM), and appendicular skeletal muscle (ASM) decreased with age in both sexes. ASM decreased relative to FFM in both the men and the women, while BCM decreased relative to FFM in the women only. Total fat mass and percent body fat decreased with age in the women, but not in the men. Body fat distribution did not appear to change with age. Anthropometric indices, muscle area and waist/hip ratio, had low correlations with muscle mass and fat distribution. CONCLUSIONS: "Sarcopenia," or muscle loss, continues to occur into old age, and may have significant impacts on physical function and health status. New anthropometric techniques are needed for assessing muscle loss with age.

Adipose Tissue↗
PubMed1994

Predictive accuracy of bioelectrical impedance in estimating body composition of Native American women.

The predictive accuracy of race-specific and fatness-specific bioelectrical impedance analysis (BIA) equations for estimating criterion fat-free mass (FFM) derived from two-component (2C) and multicomponent (MC) models was examined. Body density (Db) of Native American women (n = 151) aged 18-60 y was measured by hydrostatic weighing at residual volume. Total body bone ash was obtained by dual-energy, x-ray absorptiometry. Cross-validation of the Rising (5), Segal (3), and Gray (4) equations against FFM2C yielded high correlation coefficients (0.86-0.95) and acceptable SEEs (1.47-2.72 kg). Cross-validation of these equations against criterion FFMMC, with Db adjusted for total body mineral, yielded similar correlation coefficients (0.82-0.94) and SEEs (1.69-2.80 kg). However, each BIA equation significantly overestimated FFMMC. A new race-specific BIA equation based on an MC model was developed: FFMMC = 0.001254(HT2)-0.04904(R) + 0.1555(WT) + 0.1417(Xc) - 0.0833(AGE) + 20.05 (R = 0.864, and SEE = 2.63 kg).

Adolescent↗
PubMed1994

Differences between young and old females in the five levels of body composition and their relevance to the two-compartment chemical model.

BACKGROUND: Body composition differs between young and old females, although the magnitude of these age-related changes remains uncertain. This uncertainty persists because methodology applied in earlier studies required assumptions that may be age-dependent and also because studies included young and old subjects who differed substantially in body size and health status. METHODS: To resolve these earlier concerns we examined components at the atomic, molecular, cellular, tissue-system, and whole body levels of body composition in 19 weight- and height-matched pairs of young (age 19-35 yrs) and old (age > 65 yrs) healthy White females. Isotope dilution, dual photon, whole-body counting, hydrodensitometry, and anthropometric methods were used either alone or in combination to produce multicomponent models. RESULTS: Old females had significantly more fat, greater truncal skinfolds and circumferences, and significantly less fat-free body mass (FFM), total body potassium (TBK), total body water (TBW), and bone mineral than did their young matched counterparts. Skeletal muscle mass was less in the old females, although the magnitude of the difference from young females varied between the three indices examined. The main assumptions (i.e., TBW/FFM = 0.73 kg/kg and density of FFM = 1.100 g/cc) which the widely used two-compartment TBW and hydrodensitometry methods are based on were not significantly different in young and old females. In contrast, the main assumed steady-state value for the two-compartment TBK method (TBK/FFM = 64.2 mmol/kg) was significantly lower (p < .001) in the old females. CONCLUSION: New approaches thus allow for a critical reexamination of body composition in elderly subjects, and these methods also give new insight into less complex widely used body composition techniques.

Adipose Tissue↗
PubMed1993

Body composition of Native-American women estimated by dual-energy X-ray absorptiometry and hydrodensitometry.

In the present sample, the Native-American women varied in age (18-60 y) and fatness (23.0-57.4% BF). The cross-validation analysis for %BF estimated by DXA for this sample yielded a high validity coefficient (r = 0.89), and the average %BFDXA (37.3%) and %BFHW (37.6%) did not differ significantly. The prediction error (3.28% BF) was less than the theoretical expected value, given the wide range in age and fatness in this sample. Thus, it appears that DXA may be a viable alternative method for estimating the %BF of a diverse group of Native-American women. The DXA method is more practical than hydrostatic weighing, especially for subjects who are uncomfortable in the water. Also, DXA estimates of bone mineral may lead to improved estimates of FFB density for different ethnic populations.

Absorptiometry, Photon↗
PubMed1993

Body composition and aging: a study by in vivo neutron activation analysis.

Human body composition can be organized into five levels; atomic, molecular, cellular, tissue-system and whole body. Six elements (carbon, nitrogen, calcium, potassium, sodium and chlorine) can be directly measured in vivo at the atomic level using three neutron-activation systems at Brookhaven National Laboratory. When combined with an estimate of total body water, the six elements can be used to quantify the major chemical components at molecular level. In the present report, we first describe the neutron-activation approach to evaluating chemical compartments in vivo. Then, we present an example of how in vivo estimates of human chemical composition can be used to study the validity of two-compartment indirect methods of quantifying total body fat in the elderly. Our studies and the work of other investigators at Brookhaven National Laboratory suggest that neutron activation analysis provides an important opportunity to study the relation between aging and changes in elemental and chemical composition of humans in vivo.

Aging↗
PubMed1992

Differences in skeletal muscle and bone mineral mass between black and white females and their relevance to estimates of body composition.

This study tested the hypothesis that black females have an increase in skeletal muscle and bone mineral mass compared with white females matched for age (+/- 5 y), weight (+/- 2 kg), height (+/- 3 cm), and menstrual status. Conventional [underwater weighing, whole body 40K counting (WBC), 3H2O dilution] and newly developed (dual-photon absorptiometry) techniques were used to provide ethnicity-independent estimates of body composition in 28 pairs of matched subjects. Black females had greater appendicular skeletal muscle (P less than 0.001), bone mineral (P less than 0.001), and total body potassium (TBK) (P = 0.05) compared with white females. Two classic coefficients used in body composition research [density of fat-free mass (FFM) for underwater weighing and TBK/FFM for WBC] differed significantly (P less than 0.05) between black and white females; currently applied coefficients underestimated fat in black females. This study confirms that black and white females differ in body composition and that errors in fat estimates occur when ethnicity is not accounted for in body composition models.

Absorptiometry, Photon↗
PubMed1992

Prediction of iron absorption based on iron status of female blood donors.

Iron stores were assessed in 27 postmenopausal healthy women who donated five units of blood (approximately 485 mL/unit) over approximately 1 y. The mean (+/- SD) age was 67.7 +/- 4.0 y and the average time between successive blood donations was approximately 10 wk (range 8-30 wk). Steady-state iron stores at entrance were 10.59 +/- 3.88 mg/kg body wt (mean +/- SD) and declined to 1.03 +/- 3.20 mg/kg by the fifth donation. Determination of iron stores was based on biochemical measures of iron status at each donation. Iron intakes were 23.3 +/- 10.1 mg/d. From these data we developed equations that can be used to predict the frequency at which healthy postmenopausal women can donate blood without becoming iron deficient. The ability of elderly women to become successful blood donors depends primarily on initial iron stores, iron intake, and frequency of donation. Women with low steady-state iron stores may be able to donate only two times per year without becoming iron deficient.

Absorption↗
PubMed1992

Appendicular skeletal muscle areas assessed by magnetic resonance imaging in older persons.

Measurements of cross-sectional muscle areas of the upper-arm and mid-thigh from MRI images were compared to corresponding estimates from anthropometric measurements of limb circumferences and skinfold thicknesses in 25 normal, healthy, elderly persons. The anthropometric method significantly overestimated actual muscle areas, and the amount of error increased systematically with level of adiposity. These results agree with those from other, similar studies using CT in younger adults, but indicate that the degree of error is 2 to 3 times greater for elderly persons. At present, there does not appear to be any simple way to "correct" the anthropometric method. Prediction methods may be developed, but these will still produce large errors for some individuals. Alternative approaches are discussed.

Adipose Tissue↗
PubMed1992

Fat distribution and blood lipids in a sample of healthy elderly people.

The cross-sectional sample consisted of data for 41 white men and 63 white women, 67-92 years of age who were healthy volunteer participants in the Aging Process Study at the University of New Mexico School of Medicine in Albuquerque, New Mexico. The variables consisted of anthropometric measures of body fatness, blood lipids and blood pressures. Correlations were computed between principal component scores, ratios of body circumferences, W/S2, blood lipid values and blood pressures for each sex. In the men, the significant correlations were of the abdomen/hip and abdomen/thigh ratios with W/S2, and the principal component scores with HDL cholesterol, triglyceride and systolic blood pressure. In the women, the abdomen/hip ratio had a low negative correlation with HDL cholesterol but a low positive correlation with triglyceride levels. The principal component scores also had low correlations with blood pressure and triglycerides. Multiple regressions were used to determine further associations between risk factors and fat distribution indices. In the men, the relationships of age and levels of body fatness with HDL cholesterol were much stronger and more complex than those with triglyceride or systolic blood pressure. In the women, only HDL cholesterol and triglyceride were associated with abdomen/hip ratio after removing the effects of overall fatness. The present findings indicate that a large abdominal circumference, implying a correspondingly large internal adipose tissue deposit, produces negative health alterations in blood lipid levels in this sample of elderly individuals. In younger adults, these changes are considered to increase the risk for cardiovascular disease.

Adipose Tissue↗
PubMed1991

Reference data on gains in weight and length during the first two years of life.

Serial data from studies of infants at the University of Iowa and from the Fels Longitudinal Study were used to develop sex-specific percentiles for increments in weight and recumbent length for selected intervals during the first 24 months of life. Weight increments are presented for 1-month intervals from birth to 6 months, 2-month intervals from birth to 12 months, and 3-month intervals from birth to 24 months. Length increments are presented for 2-month intervals from birth to 6 months, and for 3-month intervals from birth to 24 months of age. Weights and lengths at the target ages were obtained for the Iowa data by simple interpolation, and for the Fels data by fitting families of three-parameter mathematical functions to the serial data from ages 1 to 24 months. The tabular presentations are based on the Iowa data from birth to 3 months of age, on the combined Iowa and Fels data from 3 to 6 months of age, and on the Fels data from 6 to 24 months of age. We believe that these reference data will be useful in screening for deviations from normal growth and may aid in early detection of failure to thrive or excessive weight gain during early life.

Age Factors↗
PubMed1991

Body composition in elderly people: effect of criterion estimates on predictive equations.

The purposes of this study were to determine whether there are significant differences between two- and four-compartment model estimates of body composition, whether these differences are associated with aqueous and mineral fractions of the fat-free mass (FFM); and whether the differences are retained in equations for predicting body composition from anthropometry and bioelectric resistance. Body composition was estimated in 98 men and women aged 65-94 y by using a four-compartment model based on hydrodensitometry, 3H2O dilution, and dual-photon absorptiometry. These estimates were significantly different from those obtained by using Siri's two-compartment model. The differences were associated significantly (P less than 0.0001) with variation in the aqueous fraction of FFM. Equations for predicting body composition from anthropometry and resistance, when calibrated against two-compartment model estimates, retained these systematic errors. Equations predicting body composition in elderly people should be calibrated against estimates from multicompartment models that consider variability in FFM composition.

Absorptiometry, Photon↗