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S B Heymsfield

Publications and source records attributed to S B Heymsfield.

At least 109 records · Page 6Linked to original sources
PubMed1998

Fraction of carbon-free body mass as oxygen is a constant body composition ratio in men.

Although elements are the foundation of the human body, information concerning the atomic level of body composition is still limited. The aim of this study was to explore potentially constant relationships among elements found in vivo. Based on the known stoichiometries of relevant chemical components, a theoretical model was derived, suggesting the existence of a relatively constant ratio of total body oxygen to carbon-free body mass (TBO/CFM) in men. Eight elements (C, H, N, Ca, P, K, Na and Cl ) were measured in 22 healthy male subjects by using in vivo neutron activation-40K whole-body counting, and TBO was calculated as the difference between body mass and the sum of the eight measured elements. TBO (in kg) was significantly correlated with CFM (in kg): TBO = 0.829 x CFM - 1.8; r = 0.998, P < 0.001, standard error of estimate = 0.4 kg. The ratio of TBO to CFM was relatively constant, mean +/- SD at 0. 800 +/- 0.009 with a CV of 1.1%. Oxygen and carbon are the two most abundant elements in the human body. The discovery of a constant relationship between oxygen and carbon is not only helpful for understanding the atomic level of body composition, but also provides the possibility of estimating the content of specific elements in vivo.

Adult↗
PubMed1998

Techniques used in measuring human body composition.

Remarkable progress is evident in the field of body composition research. This review summarizes main body composition research concepts, examines new component measurement methodologies and identifies potential areas for future research. As the dual-energy X-ray absorptiometry is now gaining acceptance, both clinically and in the research laboratory, as a useful body composition method, particular emphasis is placed on this important approach.

Absorptiometry, Photon↗
PubMed1998

Dual-energy X-ray absorptiometry: fat estimation errors due to variation in soft tissue hydration.

Dual-energy X-ray absorptiometry (DXA) is rapidly gaining acceptance as a reference method for analyzing body composition. An important and unresolved concern is whether and to what extent variation in soft tissue hydration causes errors in DXA fat estimates. The present study aim was to develop and validate a DXA physical hydration model and then to apply this model by simulating errors arising from hypothetical overhydration states. The DXA physical hydration model was developed by first linking biological substance elemental content with photon attenuation. The validated physical model was next extended to describe photon attenuation changes anticipated when predefined amounts of two known composition components are mixed, as would occur when overhydration develops. Two overhydration models were developed in the last phase of study, formulated on validated physical models, and error was simulated for fluid surfeit states. Results indicate that systematic errors in DXA percent fat arise with added fluids when fractional masses are varied as a percentage of combined fluid + soft tissue mass. Three independent determinants of error magnitude were established: elemental content of overhydration fluid, fraction of combined fluid + soft tissue as overhydration fluid, and initial soft tissue composition. Small but systematic and predictable errors in DXA soft tissue composition analysis thus can arise with fluid balance changes.

Absorptiometry, Photon↗
PubMed1998

Total body lipid and triglyceride response to energy deficit: relevance to body composition models.

Although the study of human body composition is advancing rapidly, confusion still prevails regarding the molecular-level lipid component. Most molecular-level body composition models are presently based on the overall hypothesis that nontriglyceride lipids constitute an insignificant proportion of total body lipid. A single lipid or "fat" component consisting of triglycerides is thus assumed in most molecular-level body composition models. To test this hypothesis, the present study, carried out in adult rats, was designed to examine two questions: 1) What is the proportion of total lipids as triglycerides? and 2) Is this proportion constant or does it change with negative energy balance and weight loss produced by calorie restriction and increased exercise? Results indicated that with negative energy balance and weight loss there were progressive losses of total body triglyceride and lipid. The proportion of total lipids as triglyceride was 0.83 +/- 0.08 (SD) in control animals, with reductions at 2 and 9 wk of energy restriction [0.82 +/- 0.04 (P = NS vs. control) and 0.70 +/- 0.15 (P = 0.05)] and at 9 wk for energy restriction plus exercise [0.67 +/- 0.09 (P = 0.003)]. Nontriglyceride lipids comprised 2.8% of carcass weight at baseline and decreased to 2.2% by 9 wk of energy restriction and exercise (P = NS). Substantial differences were observed between body composition ratios expressed as percentages of the lipid-free body mass (LFM) and triglyceride-free body mass (TGFM); (e.g., total body water/LFM and TGFM in controls = 72.7 +/- 0.7 and 70.4 +/- 2.2, respectively; P = 0.02). These observations strongly support the existence and importance of nontriglyceride lipids as a body composition component that responds independently from storage triglycerides, with negative energy balance produced by food restriction and exercise.

Animals↗
PubMed1998

Organ-tissue mass measurement allows modeling of REE and metabolically active tissue mass.

Investigators have expressed interest in the associations between resting energy expenditure (REE) and body mass for over a century. Traditionally, descriptive models using regression analysis are applied, linking REE with metabolically active compartments such as body cell mass (BCM) and fat-free body mass (FFM). Recently developed whole body magnetic resonance imaging (MRI) and echocardiography methods now allow estimation of all major organs and tissue volumes in vivo. Because measured values are available for REE, BCM, and FFM content of individual organs and tissues, it should now be possible to develop energy expenditure-body composition estimation models based on MRI-measured organ-tissue volumes. Specifically, the present investigation tested the hypothesis that in vivo estimation of whole body REE, BCM, and FFM is possible using MRI- and echocardiography-derived organ volumes combined with previously reported organ-tissue metabolic rates and chemical composition. Thirteen subjects (5 females, 8 males) had REE, BCM, and FFM measured by indirect calorimetry, whole body 40K counting, and dual-energy X-ray absorptiometry, respectively. Models developed from estimated and measured variables were highly correlated, with no significant differences between those estimated and measured [e.g., calculated vs. measured REE: r = 0.92, P < 0. 001; (mean +/- SD) 6,962 +/- 1,455 and 7,045 +/- 1,450 kJ/day, respectively (P = not significant)]. Strong associations were observed between REE, individual or combined organ weights, BCM, and FFM that provide new insights into earlier observed metabolic phenomona. The present approach, the first to establish an energy expenditure-body composition link with a mechanistic model in vivo, has the potential to greatly expand our knowledge of energy expenditure-body size relationships in humans.

Adolescent↗
PubMed1998

Does adipose tissue influence bioelectric impedance in obese men and women?

Bioelectric-impedance analysis overestimates fat-free mass in obese people. No clear hypotheses have been presented or tested that explain this effect. This study tested the hypothesis that adipose tissue affects measurements of resistance by using data for whole body and body segment resistance and by using muscle, adipose tissue, and bone volumes from magnetic resonance imaging for 86 overweight and obese men and women (body mass index > 27 kg/m2; age 38.5 +/- 10.2 yr). In multiple-regression analysis, muscle volumes had strong associations with resistance, confirming that the electric currents are conducted primarily in the lean soft tissues. Subcutaneous adipose tissue had a slight but statistically significant effect in women, primarily for the leg, suggesting that adipose tissue can affect measured resistance when the volume of adipose tissue is greater than muscle volume, as may occur in obese women in particular. This resulted in a slight overestimation of fat-free mass (e.g., +3 kg) when a bioelectric-impedance-analysis equation calibrated for nonobese female subjects was applied.

Adipose Tissue↗
PubMed1998

Cadaver validation of skeletal muscle measurement by magnetic resonance imaging and computerized tomography.

Magnetic resonance imaging (MRI) and computerized tomography (CT) are promising reference methods for quantifying whole body and regional skeletal muscle mass. Earlier MRI and CT validation studies used data-acquisition techniques and data-analysis procedures now outdated, evaluated anatomic rather than adipose tissue-free skeletal muscle (ATFSM), studied only the relatively large thigh, or found unduly large estimation errors. The aim of the present study was to compare arm and leg ATFSM cross-sectional area estimates (cm2) by using standard MRI and CT acquisition and image-analysis methods with corresponding cadaver estimates. A second objective was to validate MRI and CT measurements of adipose tissue embedded within muscle (interstitial adipose tissue) and surrounding muscle (subcutaneous adipose tissue). ATFSM area (n = 119) by MRI [38.9 +/- 22.3 (SD) cm2], CT (39.7 +/- 22.8 cm2), and cadaver (39.5 +/- 23.0 cm2) were not different (P > 0.001), and both MRI and CT estimates of ATFSM were highly correlated with corresponding cadaver values [MRI: r = 0.99, SE of estimate (SEE) 3.9 cm2, P < 0.001; and CT: r = 0.99, SEE = 3.8 cm2, P < 0.001]. Similarly good results were observed between MRI- and CT-measured vs. cadaver-measured interstitial and subcutaneous adipose tissue. For MRI-ATFSM the intraobserver correlation for duplicate measurements in vivo was 0. 99 [SEE = 8.7 cm2 (2.9%), P < 0.001]. These findings strongly support the use of MRI and CT as reference methods for appendicular skeletal muscle, interstitial and subcutaneous adipose tissue measurement in vivo.

Adipose Tissue↗
PubMed1998

Calcium supplementation suppresses bone turnover during weight reduction in postmenopausal women.

Bone mobilization, lowering of bone mineral density (BMD), and osteoporotic fractures are recognized in postmenopausal women with weight loss. Because a high-calcium intake suppresses bone loss in peri- and postmenopausal women, the present randomized, double-blind, placebo-controlled study was designed to test the hypothesis that calcium supplementation prevents net bone mobilization and consequent bone mineral loss during voluntary weight reduction in obese postmenopausal women. Subjects were placed on a moderate energy-restricted diet and either calcium supplementation (1 g/day) or placebo for 6 months. Body weight, bone turnover markers (pyridinium cross-links), osteocalcin, and parathyroid hormone (PTH) were measured at treatment weeks 1-5, 7, 10, 13, 16, 20, and 25. Total body BMD, insulin-like growth factor, 25-hydroxyvitamin D, and sex hormone binding globulin (SHBG) were measured at baseline and week 25. The calcium supplemented (n = 15; age 60.9 +/- 9.4 years, body mass index [BMI] 33.2 +/- 4.6 kg/m2) and placebo (n = 16; age 55.8 +/- 8.3 years, BMI 32.9 +/- 4.5 kg/m2) groups lost similar amounts of weight over the study interval (10.2 +/- 5.3% vs. 10.0 +/- 5.2%) and both groups increased SHBG (p < 0.001). There was a statistical effect of calcium supplementation during weight loss to suppress pyridinium cross-links, osteocalcin, and PTH (p < 0.05, < 0.01, and < 0.05, respectively). Loss of BMD tended to be greater in the placebo group by 1.4% (p < 0.08) after weight loss. One gram per day calcium supplementation normalizes the increased calcium-PTH axis activity and the elevated bone turnover rate observed during moderate voluntary energy restriction in postmenopausal women.

Adult↗
PubMed1997

QTc interval (cardiac repolarization): lengthening after meals.

Weight reduction, either by dietary or surgical means, is associated with prolongation of the heart rate corrected QT interval (QTc = QT/R-R0.5) and, on occasion, sudden death. Screening subjects with obesity before weight loss for prolonged QTc intervals is an accepted practice, although at present, there are no guidelines for whether subjects should be fasting before electrocardiogram (EKG) evaluation. The aim of this study was to test the hypothesis that EKG QTc interval duration is independent of meal ingestion. The hypothesis was tested in 11 healthy subjects who ingested a 500-kcal formula meal. A small decrease in absolute QT interval and a steady decline in R-R interval were observed for up to 60 minutes after formula ingestion. The QTc interval increased above baseline at 15 minutes (p < 0.007) after meal, a change that persisted for the 1-hour postmeal observation period. Spectral analysis of EKG R-R intervals (low-/high-frequency amplitude ratio) indicated a change in cardiac autonomic flow after meal ingestion. The QTc interval did not lengthen and R-R low-/high-frequency amplitude ratio remained unchanged in eight subjects evaluated in a similar manner but in whom isovolumic amounts of water replaced the meal. These observations suggest that (1) cardiac repolarization changes with fasting and feeding, (2) the QTc interval is influenced by meal intake, and (3) the autonomic nervous system may play a role in meal-related QTc changes. These findings have implications for the evaluation of patients with obesity before starting and during weight loss treatment.

Adult↗
PubMed1997

Body fat and water changes during pregnancy in women with different body weight and weight gain.

OBJECTIVE: To determine the fat deposited during pregnancy in women gaining according to recommendations of the Institute of Medicine and the relationship of weight gain to fat gain in women of different starting weights (classified by their body mass index). METHODS: A cohort study of healthy, nonsmoking women, 18-36 years of age, identified during prenatal visits at three hospital clinics and one birthing center in New York City. From a pool of 432 eligible volunteers who signed a consent form, body composition measurements were performed on 200 women at weeks 14 (+/-2) and 37+ of pregnancy, and bone mineral mass was measured at 2-4 weeks postpartum. Body fat was estimated with a model that used total body water, weight, and density and bone mineral mass. RESULTS: In women gaining as recommended by the Institute of Medicine, fat gains during pregnancy for women underweight, normal weight, overweight, or obese before pregnancy were 6.0 +/- 2.6 kg, 3.8 +/- 3.4 kg, 3.5 +/- 4.1 kg, and -0.6 +/- 4.6 kg, respectively. Higher weight gain increased fat gain. Body water gain was not different among the four prepregnancy weight groups. CONCLUSION: Recommended weight gain should not cause obesity in any weight group. Underweight women will normalize their body composition if they gain as recommended, whereas obese women will have little or no change in body fat. A majority of women do not gain as recommended during pregnancy.

Adipose Tissue↗
PubMed1997

A multi-center comparison of dual energy X-ray absorptiometers: in vivo and in vitro soft tissue measurement.

OBJECTIVE: To assess intra- and inter-site soft tissue variability by dual energy X-ray absorptiometry (DXA). DESIGN: Cross-sectional trial. SETTING: Three medical research institutions. SUBJECTS: Five humans (in vivo) and four phantoms (in vitro), configured from two whole body phantoms with artificial skeletons and thickness overlays. INTERVENTIONS: Duplicate total-body DXA scans were performed on all subjects at each institution within a 15 d period. RESULTS: All intra-site coefficients of variation (CV) were < 0.5% for total tissue mass, but in vitro and in vivo Cvs were 7.2% and 2.3% for fat mass (FM) and 2.5% and 0.9% for lean mass (LM), respectively. Several total-body and regional FM and LM measurements were significantly different between sites (P < 0.05), with percent differences between sites ranging from 2.6-13.3% for FM and from 1.6-13.6% for LM. Site 2 was consistently lower for FM and Site 3 was consistently lower for LM. CONCLUSIONS: These results stress the need for both rigorous and standardized cross-calibration procedures for soft tissue measurement by DXA.

Absorptiometry, Photon↗
PubMed1997

Electrocardiographic QTC interval: short-term weight loss effects.

OBJECTIVE: Prolongation of the QTc interval is a risk-factor for ventricular arrhythmias and sudden death. There is a correlation between body mass index (BMI) and QTc, with longer intervals observed in obese subjects. Dieting and weight loss on selected diets are also associated with prolongation of the QTc interval, although the mechanisms and risk factors of this syndrome are not clearly established. The aim of the current investigation was to determine if short-term weight loss over seven days while living on a metabolic ward influences cardiac repolarization as indicated by QT interval duration. DESIGN AND SUBJECTS: The electrocardiogram QT, RR, and QTc (QT/RR(0.5)) intervals were assessed in 30 healthy obese (BMI > 27 kg/m2) men and women ingesting a balanced 1120 kcal/d formula diet (23% kcal as fat and 52 g protein/d). RESULTS: Weight loss (3.9 +/- 1.7 kg) over seven days had no measurable effect on the RR interval and there was a significant (P = 0.02) shortening of the QT interval (mean +/- s.d., 0.395 +/- 0.028-0.386 +/- 0.027 s) and borderline significant (P = 0.11) shortening of the QTc (0.411 +/- 0.028-0.404 +/- 0.025 s) interval. The QTc interval normalized in three subjects with prolonged baseline QTc (> 0.44 s). A statistically significant (P = 0.007) reduction in systolic blood pressure early in the course of weight loss (day 2) accompanied the electrocardiographic changes. CONCLUSION: These results fail to support the development of cardiac repolarization abnormalities in obese patients who ingest a nutritionally balanced low calorie diet over seven days. A significant reduction in QT interval duration and amelioration of abnormally prolonged baseline QTc intervals suggest improved cardiac repolarization with early weight loss.

Adult↗
PubMed1997

Body mass index and all-cause mortality among people age 70 and over: the Longitudinal Study of Aging.

OBJECTIVES: To assess the relationship between body mass index (BMI; kg/m2) and mortality in a large nationally representative sample of US adults over age 70 years. DESIGN: Prospective longitudinal cohort study, the Longitudinal Study of Aging (LSOA). Subjects were all those 7260 black and white people (2769 men, 4491 women) initially interviewed in 1984 for whom height and weight were available. These subjects were followed through to 1990. MEASUREMENTS: Measurements included self-reported height and weight, date of death if subjects died, sex, age, race, measures of socio-economic status, number of living first degree relatives, and responses to questions asking whether the subject had retired due to poor health, had difficulty eating, worried about their health, and felt their health was worse than during the prior year. Smoking status was not assessed. RESULTS: When analyzed via Cox proportional hazard regression, the relationship between BMI and mortality, represented by means of hazard ratio, was clearly U-shaped for both men and women. The base of the curves was fairly wide suggesting that a broad range of BMIs are well tolerated by older adults. The minimum mortality (estimated from the fitted proportional hazard models) occurred at a BMI of approximately 31.7 for women and 28.8 for men. The results were essentially unchanged, if analyses were weighted, if various disease states were controlled for, and if apparently unhealthy subjects were excluded. CONCLUSIONS: The finding of the relatively high BMI (27-30 for men, 30-35 for women) associated with minimum hazard in persons older than seventy years supports some previously documented findings and opposes others and, if confirmed in future research, has implications for public health and clinical recommendations.

Aged↗
PubMed1997

Resting metabolic rate in obese, premenopausal black women.

In the United States, obesity is more prevalent in black than in non-Hispanic white women. Because low resting metabolic rate (RMR) has been suggested as a risk factor for weight gain, we compared RMR in 22 black and 20 white obese [body mass index (BMI; in kg/m2) range: 28.9-48.6 and 26.9-44.1, respectively], weight-stable, premenopausal, nondiabetic women. RMR was measured on two or three different occasions within a 1-wk period. The black and white groups did not differ significantly in age, degree of fitness, BMI, fat mass, or fat-free mass (FFM). In each group, RMR was predicted independently by FFM but not by age, degree of fitness, body fat mass, or body fat distribution. The slopes of the equations predicting RMR from FFM in black and white groups were not significantly different. However, the black women had significantly lower RMRs than the white women after adjustment for FFM measured by five body-composition models: dual-photon X-ray absorptiometry (DXA), hydrodensitometry, total body water, a three-compartment model, a four-compartment model, as well as for the absolute total-body potassium content as a measure of metabolically active FFM. By each analysis, the black women had significantly lower (P < 0.01) FFM-adjusted RMR than the white women; this difference ranged from 671 to 889 kJ/d depending on the body-composition method used to estimate FFM. This could contribute to the difference in the prevalence of obesity in the populations represented by these groups.

Adipose Tissue↗
PubMed1997

Effects of strength or aerobic training on body composition, resting metabolic rate, and peak oxygen consumption in obese dieting subjects.

Given that resting metabolic rate (RMR) is related largely to the amount of fat-free mass (FFM), the hypothesis was that strength training, which stimulates muscle hypertrophy, would help preserve both FFM and RMR during dieting. In a randomized controlled intervention trial, moderately obese subjects (aged 19-48 y) were assigned to one of three groups: diet plus strength training, diet plus aerobic training, or diet only. Sixty-five subjects (25 men and 40 women) completed the study. They received a formula diet with an energy content of 70% of RMR or 5150 +/- 1070 kJ/d (x +/- SD) during the 8-wk intervention. They were seen weekly for individual nutritional counseling. Subjects in the two exercise groups, designed to be isoenergetic, trained three times per week under supervision. Those in the strength-training group performed progressive weight-resistance exercises for the upper and lower body. Those in the aerobic group performed alternate leg and arm cycling. After 8 wk, the mean amount of weight lost, 9.0 kg, did not differ significantly among groups. The strength-training group, however, lost significantly less FFM (P < 0.05) than the aerobic and diet-only groups. The strength-training group also showed significant increases (P < 0.05) in anthropometrically measured flexed arm muscle mass and grip strength. Mean RMR declined significantly, without differing among groups. Peak oxygen consumption increased the most for the aerobic group (P = 0.03). In conclusion, strength training significantly reduced the loss of FFM during dieting but did not prevent the decline in RMR.

Adult↗
PubMed1997

Bioimpedance analysis: evaluation of leg-to-leg system based on pressure contact footpad electrodes.

Conventional single frequency bioimpedance analysis (BIA) systems require technician placement of arm and leg gel electrodes, a suitable location for recumbent measurements, and a separate measurement of body weight. The aim of this study was to evaluate a new single frequency 50 KHz leg-to-leg bioimpedance analysis (BIA) system combined with a digital scale that employs stainless steel pressure-contact foot pad electrodes for standing impedance and body weight measurements. Healthy adults were evaluated for 1) electrode validity and 2) potential for body component estimation. Pressure-contact foot-pad electrode measured impedance was highly correlated with (N = 9, r = 0.99, P < 0.001) impedance measured using conventional gel electrodes applied to the plantar surface of both lower extremities; mean (+/-SD) impedance was systematically higher by about 15 ohms for pressure contact electrodes (526 +/- 56 ohms vs 511 +/- 59 ohms; P < 0.001). Second, the relationship between stature-adjusted leg-to-leg impedance (H2/Z) measured by the new system and two body composition components (total body water by 3H2O dilution (N = 144); and fat-free body mass, by underwater weighing and dual x-ray absorptiometry (N = 231)) was modeled using multiple regression analysis. Correlation coefficients for H2/Z alone versus body composition components were lower for leg-to-leg BIA than for arm-to-leg BIA; correlation coefficients and SEEs became similar for the leg-to-leg and arm-to-leg BIA systems with addition of three covariates (age, gender, and waist/hip circumference ratio) to regression models. The leg-to-leg pressure contact electrode BIA system has overall performance characteristics for impedance measurement and body composition analysis similar to conventional arm-to-leg gel electrode BIA and offers the advantage of increased speed and ease of measurement.

Absorptiometry, Photon↗