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Biomedical subjects

S B Heymsfield

Publications and source records attributed to S B Heymsfield.

At least 55 records · Page 3Linked to original sources
PubMed2001

Alternative treatments for weight loss: a critical review.

"Nontraditional" or "alternative" treatments are extremely popular, especially with respect to obesity and body composition. Although such treatments are widely used, it is not clear that these are supported by the existing data in the peer-reviewed literature. Herein, we review the data on 18 methods/products advocated as potential anti-obesity/fat-reducing agents. We have found that none have been convincingly demonstrated to be safe and effective in two or more peer-reviewed publications of randomized double-blind placebo-controlled trials conducted by at least two independent laboratories. Nevertheless, some have plausible mechanisms of action and encouraging preliminary data that are sufficiently provocative to merit further research.

Anti-Obesity Agents↗
PubMed2001

Moderate energy restriction increases bone resorption in obese postmenopausal women.

BACKGROUND: Weight reduction reduces bone mineral density (BMD) and increases the risk of osteoporosis. OBJECTIVE: We investigated whether bone is mobilized in postmenopausal women during energy restriction and whether hormones regulate bone turnover and mass. DESIGN: Twenty-seven obese postmenopausal women with a mean (+/-SD) age of 55.9 +/- 7.9 y and body mass index (in kg/m(2)) of 33.0 +/- 3.8 completed the 6-mo study. Fourteen women followed a moderate energy-restricted diet (WL group) and 13 control subjects maintained their body weight (WM group). Body weight, bone turnover markers, serum parathyroid hormone (PTH), and dietary intake were measured throughout the study. Total-body BMD, sex hormone binding globulin, leptin, and estrone were measured at baseline and at week 25. RESULTS: In the WL group, body weight decreased by 10.2 +/- 5.5% (P < 0.001), body fat mass decreased by 18.7 +/- 11.3% (P < 0.001), and total-body BMD decreased by 1.2 +/- 1.2%; these changes were significantly different from those in the WM group (P < 0.05). Serial measurements showed chronically elevated rates of bone resorption and formation during energy restriction that were greater than in the WM group (P < 0.05). Serum sex hormone binding globulin increased and leptin decreased with weight loss (P < 0.05). Serum PTH tended to increase in the WL group but not in the WM group (P < 0.06). The reduction in fat mass with weight loss was directly associated with a decrease in serum estrone (P < 0.01, R(2) = 0.50). CONCLUSIONS: Moderate energy restriction increases bone turnover in obese postmenopausal women and may be regulated in part by alterations in serum PTH and estrone.

Absorptiometry, Photon↗
PubMed2001

The reconstruction of Kleiber's law at the organ-tissue level.

The relationship between resting energy expenditure (REE) (kJ/d) and body mass (M) (kg) is a cornerstone in the study of energy physiology. By expressing REE as a function of body mass observed across mammals, Kleiber formulated the now classic equation: REE = 293M(0.75). The biological processes underlying Kleiber's law have been a topic of long-standing interest and speculation. In the present report we develop a new perspective of Kleiber's law by developing an organ-tissue level REE model consisting of five components: liver, brain, kidneys, heart and remaining tissues. The resting thermal output of each component is the product of the component's specific resting metabolic rate (K) and mass (T). With increasing body size, the K values for all five components had negative exponents and were directly proportional to M(-0.08--0.27), and all component T values were directly proportional to M(0.76-1.01). The resulting exponents of the product (K x T) were M(0.60-0.86) for the five components. Although the (K x T) values of individual components do not scale equally, their combined formula (286M(0.76)) is similar to that observed by Kleiber on the whole-body level. Modeling mammalian REE at the organ-tissue level provides new insights and pathways for future mechanistic explorations of REE-body composition relationships.

Animals↗
PubMed2001

Skeletal muscle mass and aging: regional and whole-body measurement methods.

Skeletal muscle is a large compartment that can now be quantified using research and clinically applicable regional and whole-body methods. The most important advances are the two imaging methods, computed tomography (CT) and magnetic resonance imaging (MRI). Both CT and MRI can serve as regional and whole-body reference methods when evaluating other approaches for estimating skeletal muscle mass. Imaging methods also afford the opportunity to quantify both anatomic skeletal muscle and the smaller adipose-tissue free skeletal muscle component. Other available methods for estimating skeletal muscle, either regional or at the whole body level, include dual-energy x-ray absorptiometry, in vivo neutron activation analysis-whole body counting, anthropometry, ultrasound, bioimpedance analysis, and urinary metabolite markers. Each method is reviewed in the context of the aging process, cost, availability, practicality, and desired accuracy. New insights should be possible when skeletal muscle mass, measured using these methods, is combined with other descriptors of muscle biochemical and mechanical function.

Absorptiometry, Photon↗
PubMed2001

Unreliable use of standard muscle hydration value in obesity.

Intramuscular water content is assumed to be constant in humans independent of their anthropometric characteristics. To verify whether this assumption is correct, intramuscular water, proteins, glycogen, and both total and intramyocytic triglycerides were measured in 51 samples of rectus abdominis muscle obtained from 16 lean and 35 overweight and obese subjects (body mass index cutoff 24.9 kg/m2). Data (referred to as wet tissue) were analyzed by means of a composition model at the cellular level of the skeletal muscle (SM). The average SM water content was 76.3 +/- 3.3% in normal-weight individuals and 65.7 +/- 5.8% in obese subjects (P < 0.0001). Total triglycerides were 5.5 +/- 2.3% in controls and 19.0 +/- 7.0% in obese subjects (P < 0.0001). The intramyocytic triglyceride fraction was also increased in obese subjects. The composition model provides an explanation for the negative correlation between total triglycerides and intramuscular water, and some of the model parameters were determined from the experimental data. In conclusion, although the hydration of fat-free SM mass may be unchanged in obese subjects, the hydration of in toto muscle mass decreases as its lipid content increases.

Adult↗
PubMed2001

Magnitude and variation of ratio of total body potassium to fat-free mass: a cellular level modeling study.

Potassium is an essential element of living organisms that is found almost exclusively in the intracellular fluid compartment. The assumed constant ratio of total body potassium (TBK) to fat-free mass (FFM) is a cornerstone of the TBK method of estimating total body fat. Although the TBK-to-FFM (TBK/FFM) ratio has been assumed constant, a large range of individual and group values is recognized. The purpose of the present study was to undertake a comprehensive analysis of biological factors that cause variation in the TBK/FFM ratio. A theoretical TBK/FFM model was developed on the cellular body composition level. This physiological model includes six factors that combine to produce the observed TBK/FFM ratio. The ratio magnitude and range, as well as the differences in the TBK/FFM ratio between men and women and variation with growth, were examined with the proposed model. The ratio of extracellular water to intracellular water (E/I) is the major factor leading to between-individual variation in the TBK/FFM ratio. The present study provides a conceptual framework for examining the separate TBK/FFM determinants and suggests important limitations of the TBK/FFM method used in estimating total body fat in humans and other mammals.

Adipose Tissue↗
PubMed2001

Bone turnover and density in obese premenopausal women during moderate weight loss and calcium supplementation.

Bone turnover is increased during weight loss in postmenopausal women and can be suppressed with calcium supplementation. In this study, we assessed the influence of energy restriction with and without calcium supplementation (1 g/day) in premenopausal women. Thirty-eight obese premenopausal women (body mass index [BMI] of 35.0 +/- 3.9 kg/m2) completed a 6-month study of either moderate weight loss or weight maintenance. During weight loss, women were randomly assigned to either a calcium supplementation (n = 14) or placebo group (n = 14) and lost 7.5 +/- 2.5% of their body weight. The control group of women (n = 10) maintained their body weight. Total body and lumbar bone mineral density (LBMD) and content were measured by dual-energy X-ray absorptiometry (DXA) at baseline and after weight loss. Throughout the study, blood and urine samples were collected to measure bone turnover markers and hormones. During moderate energy restriction, dietary calcium intake decreased (p < 0.05) and the bone resorption marker deoxypyridinoline (DPD) increased slightly (p < or = 0.05) without evidence of bone loss. Calcium supplementation during weight loss tended to increase lumbar BMD by 1.7% (p = 0.05) compared with the placebo or weight maintenance groups. In contrast to our previous findings in postmenopausal women, premenopausal obese women who consume a low calcium diet do not lose bone over a 6-month period, whether their weight is stable or decreasing moderately.

Absorptiometry, Photon↗
PubMed2000

Effects of weight loss with orlistat on glucose tolerance and progression to type 2 diabetes in obese adults.

BACKGROUND: Orlistat is a gastrointestinal lipase inhibitor that reduces dietary fat absorption by approximately 30%, promotes weight loss, and may reduce the risk of developing impaired glucose tolerance and type 2 diabetes in obese subjects. OBJECTIVE: To test the hypothesis that orlistat combined with dietary intervention improves glucose tolerance status and prevents worsening of diabetes status more effectively than placebo. METHODS: We pooled data from 675 obese (body mass index, 30-43 kg/m2) adults at 39 US and European research centers in 3 randomized, double-blind, placebo-controlled multicenter clinical trials. Subjects received placebo plus a low-energy diet during a 4-week lead-in period. On study day 1, the diet was continued, and subjects were randomized to receive placebo 3 times a day (n=316) or treatment with orlistat, 120 mg 3 times a day (n=359), for 104 weeks. A standard 3-hour oral glucose tolerance test was performed on day 1 and at the end of treatment. MAIN OUTCOME MEASURES: The categorical assessment of glucose tolerance status (normal, impaired, diabetic) and changes in status from randomization to end of treatment were the primary efficacy measures. The secondary measures were fasting and postchallenge glucose and insulin levels. RESULTS: The mean length of follow-up was 582 days. Subjects who were treated with orlistat lost more weight (mean +/- SEM, 6.72 +/- 0.41 kg from initial weight) than subjects who received placebo (3.79+/-0.38 kg; P<.001). A smaller percentage of subjects with impaired glucose tolerance at baseline progressed to diabetic status in the orlistat (3.0%) vs placebo (7.6%) group. Conversely, among subjects with impaired glucose tolerance at baseline, glucose levels normalized in more subjects after orlistat treatment (71.6%) vs placebo (49.1%; P=.04). CONCLUSIONS: The addition of orlistat to a conventional weight loss regimen significantly improved oral glucose tolerance and diminished the rate of progression to the development of impaired glucose tolerance and type 2 diabetes.

Adult↗
PubMed2000

Anthropometry and methods of body composition measurement for research and field application in the elderly.

Evaluation of body composition is important in the study of human energy and protein metabolism as methods are available for quantifying energy stores and protein content at a single point in time; energy-protein balance can be monitored over time; and dynamic measures of energy and protein metabolism can be referenced to body mass and related measurable components for between-individual comparisons. This review emphasizes the need for considering subject age when developing body composition component prediction models that are applied in elderly populations. An overview of body composition research is provided that emphasizes compartment and level definitions and interrelations. Two broad method categories, mechanistic and descriptive, are then critically examined in relation to their role in energy-protein metabolism and aging research. Our collective review indicates that all major body composition components are now measurable using one or more methods that are based on non age-dependent assumptions. We also found that some methods, particularly descriptive field methods (eg anthropometry), may be based on age-sensitive assumptions and measurements and suggestions for future development of these methods are provided. Lastly, as body composition differences between races, cultures, and countries are now recognized, it would be useful to create international cooperative groups with the aim of developing widely applicable descriptive field methods based on simple available techniques such as anthropometry and bioimpedance analysis.

Aged↗
PubMed2000

Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index.

BACKGROUND: Although international interest in classifying subject health status according to adiposity is increasing, no accepted published ranges of percentage body fat currently exist. Empirically identified limits, population percentiles, and z scores have all been suggested as means of setting percentage body fat guidelines, although each has major limitations. OBJECTIVE: The aim of this study was to examine a potential new approach for developing percentage body fat ranges. The approach taken was to link healthy body mass index (BMI; in kg/m(2)) guidelines established by the National Institutes of Health and the World Health Organization with predicted percentage body fat. DESIGN: Body fat was measured in subjects from 3 ethnic groups (white, African American, and Asian) who were screened and evaluated at 3 universities [Cambridge (United Kingdom), Columbia (United States), and Jikei (Japan)] with use of reference body-composition methods [4-compartment model (4C) at 2 laboratories and dual-energy X-ray absorptiometry (DXA) at all 3 laboratories]. Percentage body fat prediction equations were developed based on BMI and other independent variables. RESULTS: A convenient sample of 1626 adults with BMIs < or =35 was evaluated. Independent percentage body fat predictor variables in multiple regression models included 1/BMI, sex, age, and ethnic group (R: values from 0.74 to 0.92 and SEEs from 2.8 to 5.4% fat). The prediction formulas were then used to prepare provisional healthy percentage body fat ranges based on published BMI limits for underweight (<18.5), overweight (> or =25), and obesity (> or =30). CONCLUSION: This proposed approach and initial findings provide the groundwork and stimulus for establishing international healthy body fat ranges.

Absorptiometry, Photon↗
PubMed2000

Total-body skeletal muscle mass: development and cross-validation of anthropometric prediction models.

BACKGROUND: Skeletal muscle (SM) is a large body compartment of biological importance, but it remains difficult to quantify SM with affordable and practical methods that can be applied in clinical and field settings. OBJECTIVE: The objective of this study was to develop and cross-validate anthropometric SM mass prediction models in healthy adults. DESIGN: SM mass, measured by using whole-body multislice magnetic resonance imaging, was set as the dependent variable in prediction models. Independent variables were organized into 2 separate formulas. One formula included mainly limb circumferences and skinfold thicknesses [model 1: height (in m) and skinfold-corrected upperarm, thigh, and calf girths (CAG, CTG, and CCG, respectively; in cm)]. The other formula included mainly body weight (in kg) and height (model 2). The models were developed and cross-validated in nonobese adults [body mass index (in kg/m(2)) < 30]. RESULTS: Two SM (in kg) models for nonobese subjects (n = 244) were developed as follows: SM = Ht x (0.00744 x CAG(2) + 0.00088 x CTG(2) + 0.00441 x CCG(2)) + 2.4 x sex - 0.048 x age + race + 7.8, where R:(2) = 0.91, P: < 0.0001, and SEE = 2.2 kg; sex = 0 for female and 1 for male, race = -2.0 for Asian, 1.1 for African American, and 0 for white and Hispanic, and SM = 0.244 x BW + 7.80 x Ht + 6.6 x sex - 0.098 x age + race - 3.3, where R:(2) = 0.86, P: < 0.0001, and SEE = 2.8 kg; sex = 0 for female and 1 for male, race = -1.2 for Asian, 1.4 for African American, and 0 for white and Hispanic. CONCLUSION: These 2 anthropometric prediction models, the first developed in vivo by using state-of-the-art body-composition methods, are likely to prove useful in clinical evaluations and field studies of SM mass in nonobese adults.

Adult↗
PubMed2000

Body composition modeling. Application to exploration of the resting energy expenditure fat-free mass relationship.

There are now many published methods for predicting resting energy expenditure (REE) from measured body mass and composition. Although these published reports extend back almost a century, new related studies appear on a regular basis. It remains unclear what the similarities and differences are between these many methods and what, if any, advantages the newly introduced REE prediction models offer. These issues led us to develop an organizational system for REE prediction methods with the ultimate aim of clarifying prevailing ambiguities in the field. Our classification scheme is founded on the mathematical function type (descriptive and mechanistic) and body composition level (whole body-->molecular) used in REE prediction model development. The model is applied in an exploration of the well-established empirical relationship between REE and fat-free body mass (FFM). The developed relationships indicate that REE vs. FFM is a curvilinear relationship in mammals as a whole, that the relationship can be described as a linear function in humans, and that the simple linear regression line coefficients can be reconstructed from established tissue-system level component relationships. Our classification system, the first founded on a conceptual basis, highlights similarities and differences between the many diverse REE body composition prediction methods, provides a framework for teaching REE-body composition relationships to students, and suggests important future research opportunities.

Adipose Tissue↗
PubMed2000

Cellular-level body composition model. A new approach to studying fat-free mass hydration.

Fat-free mass hydration, the ratio of total body water (TBW) to fat-free mass (FFM), is stable at approximately 0.73 in mammals, and this constancy provides a means of estimating total body fat in vivo. As there is no mechanistic theory to explain the magnitude and variability in TBW/FFM, the present investigation describes a cellular-level model indicating that FFM hydration is determined by four factors: body cell mass hydration, extracellular fluid hydration, ratio of extracellular solids to TBW, and ratio of extracellular water to intracellular water. According to the model, TBW/FFM can be predicted for adult humans as a mean of 0.73, and a variation range 0.69-0.77. The suggested modeling approach provides a conceptual framework for TBW-fat estimation method and identifies important areas that remain to be studied.

Adipose Tissue↗
PubMed2000

Smaller organ tissue mass in the elderly fails to explain lower resting metabolic rate.

We previously reported our in vivo prediction of whole body resting energy expenditure (REE) using magnetic resonance imaging and echocardiography-derived organ volumes combined with published organ tissue metabolic rates. The models, developed in young healthy persons from predicted and measured variables, were highly correlated (e.g., calculated vs. measured REE, r = 0.92, p < 0.001), with no significant differences (p = NS) between them. This study employed the same approach to determine whether possible age-related decreases in organ tissue mass may account for the lower REE commonly reported in elderly persons. Measurements of REE (REEm) were acquired by indirect calorimetry. Calculated REE (REEc) models were developed from measured tissues and organs, and energy flux rates were assigned for each of the seven tissue/organ components, as reported by Elia. Older men (n = 6) and women (n = 7) had significantly lower REEm compared to REEc (p = 0.001). The magnitude of the differences were 13% and 9.5%, respectively, for men and women. These preliminary data suggest that factors other than organ atrophy may contribute to the lower metabolic rate of older persons. Further studies are required to investigate whether there is a reduction in the oxidative capacity of individual organs and tissues.

Absorptiometry, Photon↗