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Biomedical subjects

S Heymsfield

Publications and source records attributed to S Heymsfield.

At least 19 recordsLinked to original sources
PubMed2005

Segment-specific resistivity improves body fluid volume estimates from bioimpedance spectroscopy in hemodialysis patients.

Discrepancies in body fluid estimates between segmental bioimpedance spectroscopy (SBIS) and gold-standard methods may be due to the use of a uniform value of tissue resistivity to compute extracellular fluid volume (ECV) and intracellular fluid volume (ICV). Discrepancies may also arise from the exclusion of fluid volumes of hands, feet, neck, and head from measurements due to electrode positions. The aim of this study was to define the specific resistivity of various body segments and to use those values for computation of ECV and ICV along with a correction for unmeasured fluid volumes. Twenty-nine maintenance hemodialysis patients (16 men) underwent body composition analysis including whole body MRI, whole body potassium (40K) content, deuterium, and sodium bromide dilution, and segmental and wrist-to-ankle bioimpedance spectroscopy, all performed on the same day before a hemodialysis. Segment-specific resistivity was determined from segmental fat-free mass (FFM; by MRI), hydration status of FFM (by deuterium and sodium bromide), tissue resistance (by SBIS), and segment length. Segmental FFM was higher and extracellular hydration of FFM was lower in men compared with women. Segment-specific resistivity values for arm, trunk, and leg all differed from the uniform resistivity used in traditional SBIS algorithms. Estimates for whole body ECV, ICV, and total body water from SBIS using segmental instead of uniform resistivity values and after adjustment for unmeasured fluid volumes of the body did not differ significantly from gold-standard measures. The uniform tissue resistivity values used in traditional SBIS algorithms result in underestimation of ECV, ICV, and total body water. Use of segmental resistivity values combined with adjustment for body volumes that are neglected by traditional SBIS technique significantly improves estimations of body fluid volume in hemodialysis patients.

Algorithms↗
PubMed2003

Some aspects of measuring levels of potassium in the brain.

The general aim of this work is to measure brain potassium (K) levels as a marker of intracellular water content and to test the hypothesis of whether edema in multiple sclerosis (MS) is associated with increased intracellular brain water. For that purpose, a system to measure K in brain is being developed. Our specific aim is to assess the potential contribution to the K photopeak from cranial K located outside the brain. For this, a simplified spherical phantom to represent the brain, a square box to represent the cranium, and a K point source to assess the contributions due to K outside the brain were used. It is estimated that only about 1-2% of the K photopeak might be attributable to K outside the brain.

Brain Chemistry↗
PubMed2001

Meeting summary.

Explore the source record for details and available documents.

Body Weight↗
PubMed2001

Caloric restriction mimetics: physical activity and body composition changes.

As the only paradigm that has consistently increased life span and inhibited the onset and/or progression of disease, dietary restriction has multiple effects on a variety of organ systems. In this brief review, the goal of the panel was to attempt to understand the role of changes in physical activity and body composition as possible modulators of the life span in experimental animals and humans. We focus on whether changes in exercise behavior and body composition produce similar changes as those found in dietary restriction and whether these changes can be used to either replace or enhance the beneficial effects of dietary restriction. The complexity of the two stimuli is emphasized in our report, with suggestions offered on how to better interpret existing research. Our panel briefly examines evidence in experimental animals and humans about the specific contributions of each of these factors to altering life span and age-related pathologies. We also discuss additional animal studies and/or human intervention studies that could be performed to clarify these issues. Finally, we provide suggested avenues for future research in this area of changes in physical activity and body composition as dietary restriction mimetics.

Animals↗
PubMed2000

Gamma resonance absorption. New approach in human body composition studies.

The main stream of body elemental analysis is based on the delayed, prompt, and inelastic neutron interactions with the main elements found in the human body, and subsequent analysis of the measured delayed or prompt gamma ray spectra. This methodology traditionally was, and still is, applied for whole body analysis and requires relatively high radiation doses. A new method, based on gamma nuclear resonance absorption (GNRA), is being established at Brookhaven National Laboratory as part of its body composition program. The method is element specific with a high tomographic spatial-resolution capability, at a small fraction of the radiation dose used in the current system. The new system, with its components and capabilities, is described below.

Adult↗
PubMed1999

Identification and functional analysis of novel human melanocortin-4 receptor variants.

Inactivation of the melanocortin-4 receptor (MC4-R) by gene-targeting results in mice that develop maturity-onset obesity, hyperinsulinemia, and hyperglycemia. These phenotypes resemble common forms of human obesity, which are late-onset and frequently accompanied by NIDDM. It is not clear whether sequence variation of the MC4-R gene contributes to obesity in humans. Therefore, we examined the human MC4-R gene polymorphism in 190 individuals ascertained on obesity status. Three allelic variants were identified, including two novel ones, Thr112Met and Ile137Thr. To analyze possible functional alterations, the variants were cloned and expressed in vitro and compared with the wild-type receptor. One of the novel variants, Ile137Thr, identified in an extremely obese proband (BMI 57), was found to be severely impaired in ligand binding and signaling, raising the possibility that it may contribute to development of obesity. Furthermore, our results also suggest that sequence polymorphism in the MC4-R coding region is unlikely to be a common cause of obesity in the population studied, given the low frequency of functionally significant mutations.

Adolescent↗
PubMed1997

Body fat distribution before and after weight gain in anorexia nervosa.

OBJECTIVE: To study abdominal fat distribution in anorexia nervosa subjects and to assess the effects of initial weight regain on abdominal fat distribution. DESIGN: Longitudinal, clinical study. The baseline measurement was acquired within four days of admission to the eating disorders clinic. All patients were treated by re-feeding, reinforced by psychotherapy. Following weight regain of at least 5 kg, a second body fat distribution evaluation was performed. Of the 21 subjects evaluated at baseline, 14 achieved the goal of body weight regain and were retested. PATIENTS: Fourteen subjects (age: 18-38 y; body mass index: 11.5-18.3; relative body weight: 54.9-88.3%). MEASUREMENTS: Total, subcutaneous and visceral abdominal adipose tissue areas at the L4-L5 level were evaluated by computed tomography. RESULTS: At baseline the subjects showed a higher proportion of visceral adipose tissue (% visceral adipose tissue = 55.3 +/- 26.1). A significant association was observed between body weight and both subcutaneous adipose tissue and total adipose tissue. A regain of body weight of 7.3 +/- 1.6 kg was accompanied by a significant increase in total adipose tissue, comprising both subcutaneous and visceral adipose tissue. The increase observed in subcutaneous adipose tissue, however, was significantly greater than for visceral adipose tissue (212.6% vs 116.8%, respectively, P < 0.01). CONCLUSION: The results of the current study show a higher proportion of visceral adipose tissue than subcutaneous adipose tissue in anorexia nervosa subjects. With regain of body weight there is a preferential regain of subcutaneous adipose tissue. These data demonstrate a redistribution of abdominal adipose tissue with weight regain in anorexia nervosa subjects.

Abdomen↗
PubMed1997

Obesity solutions: report of a meeting.

A workshop entitled "Obesity Solutions" was held on January 11, 1996, at St. Luke's-Roosevelt Hospital in New York City and was jointly sponsored by the St. Luke's-Roosevelt Obesity Research Center and the Nestlé R&D Center, Inc., of New Milford, Connecticut. The purpose of the workshop was to bring together experts from the research community and the pharmaceutical and food industries to address the epidemic of obesity in the United States and offer potential solutions. The following is a report of that meeting.

Humans↗
PubMed1994

Effect of caloric restriction on colonic proliferation in obese persons: implications for colon cancer prevention.

Dietary intervention to prevent colon cancer is a major health issue. At present it is not clear which dietary factors modify colon cancer risk. Caloric restriction reduces the incidence of many spontaneous and carcinogen-induced tumors in rodents, but its role in human carcinogenesis is unknown. The relationships of body mass index (BMI), body composition, and resting metabolic rate (RMR) to colon cancer risk are also undefined. In this study involving obese persons, we measured the effect of reducing caloric intake on rectal cell proliferation, a biomarker in colon carcinogenesis, and studied the relation of BMI, body composition, and RMR to rectal cell proliferation. Colonic cell proliferation was measured in rectal biopsies from persons weighing more than 130% of ideal body weight. Follow-up biopsies were performed in patients who enrolled in and completed a 16-week behavior modification weight-reduction program in which caloric intake was reduced. Baseline measurements included body composition by total body electrical conductance, RMR, and BMI. Rectal biopsies were processed for autoradiography following incubation with [3H]thymidine. Epithelial proliferation measurements were evaluable in 35 persons at baseline and in 8 persons before and after caloric restriction. Before caloric restriction, mean (+/- SD) BMI was 38 +/- 4 kg/m2 and percentage of body fat 41 +/- 2%. Subjects reduced their caloric intake by a mean of 34 +/- 4% and their weight by 8.6 +/- 1%. Caloric restriction resulted in a 39% reduction in whole-crypt labeling index (P < 0.001) and a 57% reduction in upper crypt labeling index (P < 0.05) without reduction in crypt depth. Labeling index was unrelated to BMI, RMR, or body composition. We conclude that caloric restriction reduced rectal cell proliferation measurements--intermediate biomarkers related to colon carcinogenesis. BMI, RMR, and body composition were unrelated to colonic proliferation. Caloric restriction may have a role in colon cancer prevention.

Adult↗
PubMed1994

Asians have lower body mass index (BMI) but higher percent body fat than do whites: comparisons of anthropometric measurements.

We studied the correlations between body mass index (BMI) and percent body fat (fat%) measured by dual-photon absorptiometry (DPA) in 445 white and 242 Asian adults aged 18-94 y. In addition, comparisons in six circumferences and eight skinfold-thickness measurements between whites and Asians were made to explain the discrepancies. Although Asians had lower BMI, they were fatter than whites of both sexes. The correlations between fat% and BMI varied by BMI and sex and race. Comparisons in anthropometry show that Asians had more subcutaneous fat than did whites and had different fat distributions from whites. Asians had more upper-body subcutaneous fat than did whites. The magnitude of differences between the two races was greater in females than in males. Prediction equations developed for each sex and race, based on BMI alone, gave SEEs ranging from 4.4% to 5.7%. All were significantly improved to the range of 3.5-4.4% when age and several skinfold-thickness measurements were added.

Adipose Tissue↗
PubMed1993

The effect of psychiatric disorders on weight loss in obesity clinic patients.

Research on psychiatric disorders in obesity has indicated that obese people are not psychiatrically different from nonobese people. Few studies, however, have addressed the potential impact of psychopathology on weight control. In the present study, a consecutive sample of 37 patients presenting to a major metropolitan weight control unit were given structured diagnostic interviews (Structured Clinical Interviews for Diagnosis I and II). These patients completed one of two 12-week diet programs involving either behavior modification or liquid protein diets. After 12 weeks of a liquid protein formula diet, patients with no personality disorder lost significantly more weight than personality disordered patients; personality disordered patients on a behavioral diet tended (p < .15) to lose more weight during a 12-week diet than the patients without personality disorders. These data suggest that there are differential responses to liquid protein and behavioral diets, depending on the presence or absence of a personality disorder.

Adult↗
PubMed1988

Resting energy expenditure in lung and colon cancer.

Elevated resting energy expenditure (REE) is a possible mechanism of cancer cachexia. We measured REE by whole-body direct calorimetry in patients with colon and non-small cell lung cancer and compared the results with REE in groups of healthy subjects and in patients with anorexia nervosa, with nonmalignant gastrointestinal (GI) disease, with miscellaneous reasons for weight loss, and with chronic lung disease. The mean REE of the cancer patients was not different from healthy subjects, those with GI disease, miscellaneous causes of cachexia, and chronic lung disease, and there was no significant difference in REE between those cancer patients with weight loss and controls with weight loss, except for the anorexia nervosa patients. The REE of the anorexia nervosa patients (female) was significantly lower than the REE of females with lung cancer. Weight loss correlated with REE in female lung cancer patients. Serial comparison of REE of ten cancer patients who lost 5% to 18% of their body weight during study showed no consistent change in REE. We conclude that patients with colon and non-small cell lung cancer, including those with weight loss, have REE similar to normal controls. Relative hypermetabolism may contribute to cancer cachexia, as may absolute hypermetabolism in some subsets of cancer patients.

Anorexia Nervosa↗
PubMed1985

Bioenergetic studies in adult patients recovering from semi-starvation.

A model of energy-nitrogen balance developed in animals was adapted to the study of human bioenergetics. By creating balance conditions and steady-state formula infusion rates, each of the needed components of energy and nitrogen balance can now be measured with a high level of accuracy. A comprehensive description of energetic efficiency at the whole body level is possible using appropriate mathematical modeling. Key questions in human bioenergetics await these results, and our laboratory is currently undertaking these studies.

Adult↗
PubMed1982

Enteral hyperalimentation in undernourished patients with cirrhosis and ascites.

Available enteral hyperalimentation solutions used to treat undernourished cirrhotic, ascitic patients with protein intolerance are excessive in water, sodium, and in some cases protein. This study investigated the use of enteral formulae tailored to the water, sodium, and protein tolerance of 10 undernourished subjects with ascites due to alcoholic liver disease (n = 8) and postnecrotic cirrhosis (n = 2). During a 10- to 60-day (mean +/- 80 = 37 +/- 19) hyperalimentation period, three subjects were treated with a low Na (1g Na/2000 kcal), high caloric density formula (2 kcal/ml); previous encephalopathy in seven remaining subjects required infusion of a low Na, low protein (40 g/day) modular high caloric density formula. The high caloric density formula protein content in 6/7 subjects was increased to 80 to 143 g without adverse effect. Nine subjects tolerated the program well and showed improvement in the following indices: serum albumin, creatinine/height, and midarm muscle and fat areas. In selected cases, enteral hyperalimentation solutions with appropriate composition can be safely and effectively administered to cachectic cirrhotic subjects with ascites.

Adult↗
PubMed1981

Hyperalimentation of the cancer patient with protein-calorie undernutrition.

Because protein-calorie undernutrition is common in patients with neoplastic disease, nutritional support is often recommended. It is uncertain, however, that methods of supplemental alimentation successful in noncancerous subjects are suitable in cancer patients. We measured elemental balances, serum proteins, anthropometrics (triceps skinfold and mid-arm muscle area), and creatinine/height ratio in 15 undernourished patients with advanced cancer and in 10 noncancer undernourished controls during central venous or enteral hyperalimentation and found the following. (a) During central venous hyperalimentation, cancer patients showed significantly less improvement than the noncancerous controls in body weight (median increment, 5 kg in cancer patients and 8.5 kg in noncancerous), albumin (0.1 g/dl in cancer patients and 0.5 g/dl in noncancerous patients), creatinine/height ratio (4% of standard in cancer and 10% of standard in noncancer), and mid-arm muscle area (4% of standard in cancer and 11% of standard in noncancer). During enteral hyperalimentation, gains in body weight and albumin by cancer patients were significantly inferior to those in noncancerous subjects. Triceps skinfold increments, in contrast, were similar during both central venous and enteral hyperalimentation for cancer and noncancerous patients. (b) While nitrogen retention was similar in cancer and noncancer patients, the cancer group retained significantly less magnesium and phosphorus (delta Mg in cancer patients, 3.2 mEq/day central, -2.7 mEq/day enteral; delta Mg in noncancer patients, 11.9 mEq/day central, 10.1 mEq/day enteral; delta P in cancer patients, 0.13 g/day central, 0.07 g/day enteral; delta P in noncancer patients, 0.27 g/day central, 0.33 g/day enteral). The poorer balances of cancer patients were caused by increased urinary, not fecal, loss. These findings indicate a partial block in repletion of lean body mass or abnormal composition of newly deposited lean body mass when undernourished patients with advanced cancer receive hyperalimentation.

Adult↗
PubMed1977

Reversible malignant hypertension and azotemia due to urethral stricture.

A previously normotensive 24-year-old black man developed malignant hypertension and azotemia. The patient was found to have bladder outlet obstruction due to urethral stricture. Transurethral dilation resulted in brisk improvement in renal function and rapid lowering of blood pressure in association with minimal diuresis. On follow-up one year later, while he was not receiving medications, the blood pressure was 120/70 mm Hg and the creatinine clearance was 150 ml/min. A kidney biopsy specimen showed minimal residual pathologic abnormalities in the renal arteries and arterioles. The renin-angiotensin system was probably involved in the maintenance of the hypertension, in view of the elevated peripheral plasma renin activity on admission. This represents a rare case of hypertension due to urethral stricture. Despite rapid progression to azotemic malignant hypertension, urethral dilation restored the blood pressure and renal function to normal.

Adult↗