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Biomedical subjects

S B Heymsfield

Publications and source records attributed to S B Heymsfield.

At least 91 records · Page 5Linked to original sources
PubMed1999

Hydration of fat-free body mass: review and critique of a classic body-composition constant.

The assumed "constancy" of fat-free body mass hydration is a cornerstone in the body-composition research field. Hydration, the observed ratio of total body water to fat-free body mass, is stable at approximately 0.73 in mammals and this constancy provides a means of estimating total body fat in vivo. This review examines both in vitro and in vivo data that support the hydration constancy hypothesis and provides a critique of applied methodology. Biological topics of interest are then examined and critical areas in need of future research are identified. These are important issues because water dilution is the only method currently available for estimating body fat in all mammals, which range in body mass by a factor of 10(4).

Absorptiometry, Photon↗
PubMed1999

Fat distribution in HIV-infected patients reporting truncal enlargement quantified by whole-body magnetic resonance imaging.

BACKGROUND: Antiretroviral therapy has improved the prospects for people infected with HIV, but some develop a syndrome of profound body habitus and metabolic alterations that include truncal enlargement. OBJECTIVE: The purpose of this study was to define the body-composition changes associated with this syndrome by using techniques with the power to estimate regional body composition. DESIGN: We compared whole-body and regional skeletal muscle and adipose tissue contents measured by magnetic resonance imaging and dual-energy X-ray absorptiometry (DXA) in 26 HIV-infected patients and 26 matched control subjects. Twelve of the HIV-infected patients had evidence of truncal enlargement. RESULTS: HIV-infected men and women who noted truncal enlargement had similar amounts of skeletal muscle and subcutaneous adipose tissue but greater visceral adipose tissue than HIV-infected patients without truncal enlargement; these values were larger in men (P < 0.001) than in women (P = 0.08). The ratio of visceral to subcutaneous adipose tissue was greater in both men (P < 0.02) and women (P = 0.05) with truncal enlargement. Two subjects with MRI-confirmed visceral adiposity syndrome (VAS) were not taking protease inhibitors. CD4+ lymphocyte counts were higher (P < 0.001) and plasma viral burdens tended to be lower (P = 0.08) in HIV-infected patients with VAS. CONCLUSIONS: There was significantly more visceral adipose tissue in the subgroup of HIV-infected patients with truncal enlargement than in those without this sign. VAS occurs in both men and women, is associated with higher CD4+ lymphocyte counts and lower plasma HIV viral burdens, and is not limited to those receiving protease inhibitor therapy.

Absorptiometry, Photon↗
PubMed1999

The relationship between body composition and physical performance in older women.

BACKGROUND: The relationship between age-associated change in body composition and physical disability is still unknown. Skeletal muscle mass declines with age in both sexes; however, since women have less muscle mass per unit of weight than men, these changes may be more debilitating in women. OBJECTIVE: To evaluate the relationship between body composition and physical performance. DESIGN: A cross-sectional study. PARTICIPANTS: 144 women aged 68 to 75 were selected randomly from the general population of Verona. MEASUREMENTS: Body composition was evaluated using dual energy X-ray absorptiometry and bioimpedance. Physical performance was evaluated using a modified version of the Activities of Daily Living scale. Distance walked in 6 minutes was calculated, and isometric knee strength was tested. RESULTS: Normal women had a significantly lower body mass index (BMI) and percent body fat. These women also had a higher ratio of body cell mass (BCM) and total fat free mass (FFM) than women with physical impairments. After adjusting for BMI, women in the lowest tertile of muscle strength had significantly lower BCM than those in the highest tertile. CONCLUSIONS: These cross-sectional data show that although muscle strength is related to fat-free mass, disability in older women is associated with heavier BMI and with a higher percentage of body fat.

Absorptiometry, Photon↗
PubMed1999

Hydration of fat-free body mass: new physiological modeling approach.

Water is an essential component of living organisms, and in adult mammals the fraction of fat-free body mass (FFM) as water is remarkably stable at approximately 0.73. The stability of FFM hydration is a cornerstone of the widely used water isotope dilution method of estimating total body fat. At present, the only suggested means of studying FFM hydration is by experimental total body water (TBW) and FFM measurements. Although deviations from the classical hydration constant are recognized, it is unknown if these are explainable physiological aberrations and/or methodological errors. Moreover, many questions related to hydration stability prevail, including body mass and age effects. These unresolved questions and the importance of the TBW-fat estimation method led us to develop a cellular level FFM hydration model. This physiological model reveals that four water-related ratios combine to produce the observed TBW-to-FFM ratio. The mean and range of FFM hydration observed in adult humans can be understood with the proposed physiological model as can variation in the TBW-to-FFM ratio over the human life span. An extension of the model to the tissue-organ body composition level confirms on a theoretical basis a small but systematic decrease in hydration observed in mammals ranging in body mass by a factor of 10(5). The present study, the first to advance a physiological hydration model, provides a conceptual framework for the TBW-fat estimation method and identifies important areas that remain to be studied.

Aging↗
PubMed1999

Validity of methods of body composition assessment in young and older men and women.

We examined the validity of percent body fat (%Fat) estimation by two-compartment (2-Comp) hydrostatic weighing (Siri 2-Comp), 3-Comp dual-energy X-ray absorptiometry (DEXA 3-Comp), 3-Comp hydrostatic weighing corrected for the total body water (Siri 3-Comp), and anthropometric methods in young and older individuals (n = 78). A 4-Comp model of body composition served as the criterion measure of %Fat (Heymsfield 4-Comp; S. B. Heymsfield, S. Lichtman, R. N. Baumgartner, J. Wang, Y. Kamen, A. Aliprantis, and R. N. Pierson Jr., Am. J. Clin. Nutr. 52: 52-58, 1990.). Comparison of the Siri 3-Comp with the Heymsfield 4-Comp model revealed mean differences of </=0.4 %Fat, r values >/= r = 0.997, total error values </= 0.85 %Fat, and 95% confidence intervals (Bland-Altman analysis) of </=1.7 %Fat. Comparison of Siri 2-Comp, DEXA, and anthropometric models with the Heymsfield 4-Comp revealed that total error scores ranged from +/-4. 0 to +/-10.7 %Fat, and 95% confidence intervals associated with the Bland-Altman analysis ranged from +/-5.1 to +/-15.0 %Fat. We conclude that the Siri 3-Comp model provides valid and accurate body composition data when compared with a 4-Comp criterion model. However, the individual variability associated with the Siri 2-Comp, DEXA 3-Comp, and anthropometric models may limit their use in research settings. The use of anthropometric estimation methods resulted in large mean differences and a considerable amount of interindividual variability. These data suggest that the use of these techniques should be viewed with caution.

Absorptiometry, Photon↗
PubMed1999

Regional skeletal muscle measurement: evaluation of new dual-energy X-ray absorptiometry model.

Although there is growing interest in studying muscle distribution, regional skeletal muscle (SM) mass measurement methods remain limited. The aim of the present study was to develop a new dual-energy X-ray absorptiometry (DEXA) model for estimating regional adipose tissue-free skeletal muscle mass (AT-free SM). Relationships were derived from Reference Man data between tissue-system- level components (i.e., AT-free SM, AT, skeleton, and skin) and molecular-level components including fat-free soft tissue, fat, and bone mineral. The proposed DEXA-SM model was evaluated by multiscan computerized axial tomography (CT). Twenty-seven male subjects [age, 36 +/- 12 (SD) yr; body mass, 73.2 +/- 12.4 kg; 20 were healthy, and 7 had acquired immunodeficiency syndrome] completed DEXA and CT studies. Identical landmarks for DEXA and CT measurements were selected in three regions, including calves, thighs, and forearms. There was a strong correlation for AT-free SM estimates between the new DEXA and CT methods (e.g., sum of three regions, r = 0.86, P < 0.001). Regional AT-free SM measured in the 27 subjects by DEXA and CT, respectively, were 3.44 +/- 0.60 and 3. 47 +/- 0.55 kg (difference 0.9%, P > 0.05) for calves, 10.49 +/- 1. 77 and 10.05 +/- 1.79 kg (difference 4.4%, P < 0.05) for thighs, 1. 36 +/- 0.49 and 1.20 +/- 0.41 kg (difference 13.3%, P < 0.01) for forearms, and 15.29 +/- 2.33 and 14.72 +/- 2.33 kg (difference 3.9%, P < 0.05) for the sum all three regions. Although the suggested DEXA-SM model needs minor refinements, this is a promising in vivo approach for measurement of regional SM, because DEXA is widely available, relatively inexpensive, and radiation exposure is low.

Absorptiometry, Photon↗
PubMed1999

Evidence for independent genetic influences on fat mass and body mass index in a pediatric twin sample.

OBJECTIVE: Insight into genetic and environmental influences on fat mass, independent of body mass index (BMI; kg/m2), is expected to enhance methods for treating pediatric obesity. However, few studies have estimated the heritability of fat mass in pediatric samples, and those conducted have relied primarily on BMI measurements. PRESENT STUDY: Using bioimpedance analysis, the present study tested a series of hypotheses predicting significant genetic and environmental influences on percent body fat (PBF) above and beyond BMI. Subjects were 66 pairs of twins, including 41 monozygotic and 25 dizygotic pairs, from 3 to 17 years of age. Structural equation modeling tested hypotheses, adjusting for demographic variables. RESULTS: Analyses indicated significant genetic influences on PBF, with genes estimated to account for 75% to 80% of the phenotypic variation. The remaining variation was attributable to nonshared environmental influences. Multivariate analyses revealed sizable genetic correlations and environmental correlations between BMI and PBF (rg =.74 and re =.67, respectively), suggesting that some genes and environmental experiences influence both phenotypes. However, analyses confirmed genetic and environmental influences on PBF above and beyond BMI. For example, 62.5% of the total genetic variation in PBF was attributable to genes that influenced PBF but not BMI. CONCLUSION: There seems to be a substantial genetic contribution to fat mass distinct from BMI in a sample of children and adolescents. Studies testing putative genetic or environmental determinants of pediatric obesity might be strengthened further by including research-based body composition methods.

Adipose Tissue↗
PubMed1999

Correlations between skeletal muscle mass and bone mass in children 6-18 years: influences of sex, ethnicity, and pubertal status.

A constant sex-specific relationship between skeletal muscle mass and bone mass was observed in healthy adults based on TBK/TBCa, using TBK (total body potassium) by 40K counting and TBCa (total body calcium) by in-vivo neutron activation analysis (Ellis and Cohn, 1975). We revisited this topic in children by studying correlations between TBK and TBCa, and by comparing TBK/TBCa between sexes, pubertal groups (prepubertal and pubertal) and ethnic groups in 141 white, 101 black, and 62 Asian healthy children, aged 6 - 18 years, living in New York City. TBK was measured by 40K counting, and TBCa by dual energy x-ray absorptiometry. TBK and TBCa were significantly correlated from 6 to 18 years (r > 0.93), but the correlation equations varied by gender and ethnicity. Boys had significantly more TBK and greater TBK/TBCa than girls at a given age and weight, reflecting greater skeletal muscle mass in boys from 6 years, the age at which the study started. TBK/TBCa in blacks was significantly smaller than whites and Asians in both sexes in prepuberty and puberty, and pubertal black girls had the smallest mean TBK/TBCa. No significant differences were found between whites and Asians. TBK/TBCa decreased as body weight increased in prepubertal girls, and decreased as body weight and age increased in pubertal girls, but did not change with body weight or age in boys of any subgroup. The inverse relationship between TBK/TBCa and age in pubertal girls suggests greater increase in TBCa compared to TBK than in other groups, while the constant TBK/TBCa in boys reflects proportional increases in TBK and TBCa. Thus TBK/TBCa can be used as an index of relative growth in skeletal muscle mass and bone mass in white, black, and Asian children according to sex, age and pubertal status.

Adolescent↗
PubMed1998

Garcinia cambogia (hydroxycitric acid) as a potential antiobesity agent: a randomized controlled trial.

CONTEXT: Hydroxycitric acid, the active ingredient in the herbal compound Garcinia cambogia, competitively inhibits the extramitochondrial enzyme adenosine triphosphate-citrate (pro-3S)-lyase. As a citrate cleavage enzyme that may play an essential role in de novo lipogenesis inhibition, G cambogia is claimed to lower body weight and reduce fat mass in humans. OBJECTIVE: To evaluate the efficacy of G cambogia for body weight and fat mass loss in overweight human subjects. DESIGN: Twelve-week randomized, double-blind, placebo-controlled trial. SETTING: Outpatient weight control research unit. PARTICIPANTS: Overweight men and women subjects (mean body mass index [weight in kilograms divided by the square of height in meters], approximately 32 kg/m2). INTERVENTION: Subjects were randomized to receive either active herbal compound (1500 mg of hydroxycitric acid per day) or placebo, and both groups were prescribed a high-fiber, low-energy diet. The treatment period was 12 weeks. Body weight was evaluated every other week and fat mass was measured at weeks 0 and 12. MAIN OUTCOME MEASURES: Body weight change and fat mass change. RESULTS: A total of 135 subjects were randomized to either active hydroxycitric acid (n = 66) or placebo (n = 69); 42 (64%) in the active hydroxycitric acid group and 42 (61%) in the placebo group completed 12 weeks of treatment (P = .74). Patients in both groups lost a significant amount of weight during the 12-week treatment period (P<.001); however, between-group weight loss differences were not statistically significant (mean [SD], 3.2 [3.3] kg vs 4.1 [3.9] kg; P = .14). There were no significant differences in estimated percentage of body fat mass loss between treatment groups, and the fraction of subject weight loss as fat was not influenced by treatment group. CONCLUSIONS: Garcinia cambogia failed to produce significant weight loss and fat mass loss beyond that observed with placebo.

Adult↗
PubMed1998

Epidemiology of sarcopenia among the elderly in New Mexico.

Muscle mass decreases with age, leading to "sarcopenia," or low relative muscle mass, in elderly people. Sarcopenia is believed to be associated with metabolic, physiologic, and functional impairments and disability. Methods of estimating the prevalence of sarcopenia and its associated risks in elderly populations are lacking. Data from a population-based survey of 883 elderly Hispanic and non-Hispanic white men and women living in New Mexico (the New Mexico Elder Health Survey, 1993-1995) were analyzed to develop a method for estimating the prevalence of sarcopenia. An anthropometric equation for predicting appendicular skeletal muscle mass was developed from a random subsample (n = 199) of participants and was extended to the total sample. Sarcopenia was defined as appendicular skeletal muscle mass (kg)/height2 (m2) being less than two standard deviations below the mean of a young reference group. Prevalences increased from 13-24% in persons under 70 years of age to >50% in persons over 80 years of age, and were slightly greater in Hispanics than in non-Hispanic whites. Sarcopenia was significantly associated with self-reported physical disability in both men and women, independent of ethnicity, age, morbidity, obesity, income, and health behaviors. This study provides some of the first estimates of the extent of the public health problem posed by sarcopenia.

Adult↗
PubMed1998

Do unsuccessful dieters intentionally underreport food intake?

OBJECTIVE: A bogus pipeline paradigm was utilized to assess whether food intake underreporting by unsuccessful dieters is intentional. METHOD: Twenty-eight subjects completed 1-week food diaries. Then, 17 subjects in the experimental condition kept 2-week food diaries while being told the researcher was verifying their report. Eleven subjects in the control group were asked merely to self-monitor for two more weeks. RESULTS: Results indicate that subjects in the experimental group reported significantly greater intake than control subjects, when controlling for reported intake during the screening phase and weight change. DISCUSSION: Thus, the belief that the researcher could verify their report improved the accuracy of patients' self-report. However, all subjects continued to underreport their dietary intake. In summary, underreporting may be an intentional attempt to manage presentation to others in a society that is increasingly critical of overweight persons.

Adult↗
PubMed1998

Measurement challenges and other practical concerns when studying massively obese individuals.

OBJECTIVE: To describe the measurement challenges faced and to evaluate the measurement quality obtained with massively obese individuals. METHOD: A cross-sectional analysis of 107 individuals with body mass indices (kg/m2) > or = 50 was conducted. Individuals had their body fat measured via bioimpedance analysis (BIA), their serum leptin levels measured via radioimmunoassay (RIA), and height and weight measured via both laboratory scales and self-report. RESULTS: Serum leptin appeared to be measured accurately, provided the serum was diluted prior to conducting the RIA. Difficulties remained, however, in evaluating what was an unusual or expected value of leptin among individuals this large. Measures of impedance appeared to provide reasonable ordinal indications of body fatness. However, currently available equations for converting measures of impedance to estimates of percent body fat were highly inaccurate. Self-reported height and weight were reasonably good proxies of measured height and weight among individuals who reported their height and weight. However, a substantial proportion were unable to provide estimates. DISCUSSION: The above results suggest there are substantial challenges when trying to obtain meaningful measurements regarding obesity-related variables among massively obese individuals. Other logistic challenges also are discussed. It is hoped future research is directed at overcoming some of these challenges.

Adipose Tissue↗
PubMed1998

Prader-Willi syndrome: relationship of adiposity to plasma leptin levels.

OBJECTIVE: Prader-Willi syndrome (PWS) is an autosomal dominant disorder involving the proximal long arm of chromosome 15, in which obesity is common. However, there is limited information on the underlying physiological mechanisms promoting obesity in this population. We tested whether there was a significant positive association between leptin and total body fat (TBF) in subjects with PWS, and whether this association was stronger among subjects with than without PWS. RESEARCH METHODS AND PROCEDURES: We studied 21 PWS patients and 64 non-PWS controls on whom we measured serum leptin, total body fat, glucose, insulin, and resting energy expenditure. We tested whether the slope of the regression line between leptin and TBF (in kg), measured by dual energy X-ray absorptiometry, was the same for PWS patients and non-PWS controls. RESULTS: Regression analyses indicated that the leptin-TBF association was significantly stronger among PWS patients. In contrast, the slope of the leptin-body mass index association did not significantly differ between PWS patients and non-PWS controls. None of the other outcome variables showed associations with leptin. DISCUSSION: Results suggest that the role of leptin in promoting obesity may be greater among subjects with PWS than among non-PWS controls.

Absorptiometry, Photon↗
PubMed1998

Body mass index as a measure of adiposity among children and adolescents: a validation study.

OBJECTIVES: To test the hypothesis that in a healthy pediatric population body mass index (BMI) (kilograms per meter square) is a valid measure of fatness that is independent of age for both sexes. METHODS: Total body fat (TBF) (in kilograms) and percent of body weight as fat (PBF) were estimated by dual energy x-ray absorptiometry (DXA) in 198 healthy Italian children and adolescents between 5 and 19 years of age. We developed multiple regression analysis models with TBF and percent body fat as dependent variables and BMI, age, and interaction terms as independent variables. Separate analyses were conducted for boys and girls. RESULTS: BMI was strongly associated with TBF (R2 = 0.85 and 0.89 for boys and girls, respectively) and PBF (R2 =0.63 and 0.69 for boys and girls, respectively). Confidence limits on BMI-fatness association were wide, with individuals of similar BMI showing large differences in TBF and in PBF. Age was a significant covariate in all regression models. Addition of nonlinear terms for BMI did not substantially increase the R2 for TBF and PBF models in boys and girls. CONCLUSION: Our results support the use of BMI as a fatness measure in groups of children and adolescents, although interpretation should be cautious when comparing BMI across groups that differ in age or when predicting a specific individual's TBF or PBF.

Absorptiometry, Photon↗
PubMed1998

Appendicular skeletal muscle mass: prediction from multiple frequency segmental bioimpedance analysis.

OBJECTIVES: Bioimpedance analysis (BIA) methods have potential to predict appendicular skeletal muscle mass (SM), although available 50 kHz prediction models include, in addition to impedance (Z), an independent age term. An age term in models is undesirable as it reflects incomplete understanding of underlying conduction physiology. This study tested the hypothesis, based on fluid distribution models related to aging, that appendicular SM bioimpedance analysis (BIA) prediction models would no longer include an independent age term, after first controlling for stature-adjusted appendicular impedance (height2/Z), at injected frequencies greater than 50 kHz. DESIGN: Cross-sectional evaluation of adults who had segmental Z and phase angle (phi) measured with multiple frequency BIA, and arm and leg SM with dual-energy X-ray absorptiometry (DXA). Skeletal muscle prediction models were developed with appendicular SM as dependent variable and height2/Z, gender, age and phi as potential independent variables. RESULTS: Examination of hypothesis in 49 subjects indicated: both arm and leg SM were highly correlated with height2/segmental Z at frequencies ranging from 1-300 kHz; gender was significant covariate in prediction models only at 1 kHz; age remained a significant covariate after controlling for height2/segmental Z at all frequencies; phi did not add significantly to models; and SM prediction models gave maximum R2 at 50 kHz for arm but R2 continued to rise up to 300 kHz for leg. CONCLUSION: Although multifrequency BIA did not eliminate SM prediction model age term, our findings suggest injected frequencies up to 300 kHz may have advantages for evaluating leg SM over conventional 50 kHz method.

Adult↗
PubMed1998

Six-compartment body composition model: inter-method comparisons of total body fat measurement.

OBJECTIVE: To compare 16 currently used total body fat methods to a six-compartment criterion model based on in vivo neutron activation analysis. DESIGN: Observational, inter-method comparison study. SUBJECTS: Twenty-three healthy subjects (17 male and 6 female). MEASUREMENTS: Total body water (TBW) was measured by tritium dilution; body volume by underwater weighing (UWW); total body fat and bone mineral by dual-energy X-ray absorptiometry (DXA), total body potassium (TBK) by whole-body 40K counting; total body carbon, nitrogen, calcium, phosphorus, sodium and chlorine by in vivo neutron activation analysis; skinfolds/circumferences by anthropometry (Anth); and resistance by single-frequency bioimpedance analysis (BIA). RESULTS: The average of total body fat mass measurements by the six-compartment neutron activation model was 19.7+/-10.2kg (mean+/-s.d.) and comparable estimates by other methods ranged from 17.4-24.3 kg. Although all 16 methods were highly correlated with the six-compartment criterion model, three groups emerged based on their comparative characteristics (technical error, coefficient of reliability, Bland-Altman analysis) relative to criterion fat estimates, in decreasing order of agreement: 1. multi-compartment model methods of Baumgartner (19.5+/-9.9 kg), Heymsfield (19.6+/-9.9 kg), Selinger (19.7+/-10.2 kg) and Siri-3C (19.6+/-9.9 kg); 2. DXA (20.0+/-10.8 kg), Pace-TBW (18.8+/-10.1 kg), Siri-2C (20.0+/-9.9 kg), and Brozek-UWW (19.4+/-9.2 kg) methods; and 3. Segal-BIA (17.4+/-7.2 kg), Forbes-TBN (21.8+/-10.5 kg), Durnin-Anth (22.1+/-9.5 kg), Forbes-TBK (22.9+/-11.9 kg), and Steinkamp-Anth (24.3+/-9.5 kg) methods. CONCLUSION: Relative to criterion fat estimates, body composition methods can be organized into three groups based on inter-method comparisons including technical error, coefficient of reliability and Bland-Altman analysis. These initial groupings may prove useful in establishing the clinical and research role of the many available fat estimation methods.

Absorptiometry, Photon↗
PubMed1998

Anthropometric equations for studying body fat in pregnant women.

Anthropometric data from 200 pregnant women were used to estimate body fat at gestation weeks 14 and 37 and changes in body fat from week 14 to week 37 with four formulas from the literature. The resulting estimates were evaluated against the estimation of fat by a four-compartment model that determined fat from weight, total body water, bone mineral mass, and body density. The estimates of fat by existing anthropometric models were statistically different from those by the four-compartment model in both early and late pregnancy. Most importantly, the change in body fat estimated by the anthropometric models (all > 4 kg) was considerably higher than that estimated by the four-compartment model (3.3 kg). Two new anthropometric equations were developed, both of which used the four-compartment model as the reference method. The equation for predicting change in fat mass from week 14 to 37 of pregnancy was as follows: 0.77 (change in weight, kg)+ 0.07 (change in thigh skinfold thickness, mm)-6.13 (r2 = 0.73). The equation for determining fat (kg) at term was as follows: 0.40 (weight at week 37, kg)+ 0.16 (biceps skinfold thickness at week 37, mm) + 0.15 (thigh skinfold thickness at week 37, mm)-0.09 (wrist circumference at week 37. mm)+ 0.10 (prepregnancy weight.kg)-6.56 (r2 = 0.89). Both equations were derived on a randomly selected half of the total sample and validated on the remaining half. Both equations were found to be valid for use in studying pregnant women with different prepregnancy body mass indexes, different gestational weight gains, different ethnicities, and different socioeconomic status.

Adipose Tissue↗