Biomedical subjects

S Heshka

Publications and source records attributed to S Heshka.

At least 19 recordsLinked to original sources

PubMed2006

MRI-measured bone marrow adipose tissue is inversely related to DXA-measured bone mineral in Caucasian women.

INTRODUCTION: Recent studies suggest that bone marrow adipose tissue (BMAT) might play a role in the pathogenesis of osteoporosis. Previous research using regional magnetic resonance spectroscopy methods to measure BMAT has reported inconsistent findings on the relationship between BMAT and dual-energy absorptiometry (DXA)-measured bone mineral density (BMD). METHODS: In the present study, total body and pelvic BMAT were evaluated in 56 healthy women (age 18-88 yrs, mean +/- SD, 47.4 +/- 17.6 yrs; BMI, 24.3 +/- 4.2 kg/m(2)) with T1-weighted whole-body magnetic resonance imaging (MRI). BMD was measured using the whole-body DXA mode (GE Lunar DPX, software version 4.7). RESULTS: A strong negative correlation was observed between pelvic BMAT and BMD (total-body BMD, R = -0.743, P < 0.001; pelvic BMD, R = -0.646, P < 0.001), and between total-body BMAT and BMD (total-body BMD, R = -0.443, P < 0.001; pelvic BMD, R = -0.308, P < 0.001). The inverse association between pelvic BMAT and BMD remained strong after adjusting for age, weight, total body fat, and menopausal status (partial correlation: total-body BMD, R = -0.553, P < 0.001; pelvic BMD, R = -0.513, P < 0.001). BMAT was also highly correlated with age (pelvic BMAT, R = 0.715, P < 0.001; total-body BMAT, R = 0.519, P < 0.001). CONCLUSION: MRI-measured BMAT is thus strongly inversely correlated with DXA-measured BMD independent of other predictor variables. These observations, in the context of DXA technical concerns, support the growing evidence linking BMAT with low bone density.

Absorptiometry, Photon↗

PubMed2006

Visceral adipose tissue: relationships between single slice areas at different locations and obesity-related health risks.

BACKGROUND: Visceral adipose tissue (VAT) is widely recognized as conveying the highest health risk in humans among the currently measurable adipose tissue compartments. A recent study indicated that the traditionally measured VAT area at L(4)-L(5) is not the VAT area with the highest correlation with total VAT volume. At present, it is unknown whether the area with the highest correlation is also the most strongly associated with obesity-related health risk. OBJECTIVE: The study aim was to establish which VAT slice area(s) are most strongly associated with obesity-related health risk indicators. DESIGN: The subjects were a convenience sample of healthy adults who completed whole-body magnetic resonance imaging (MRI) scans. The correlations, with appropriate adjustments, were examined between individual MRI slice VAT areas and fasting serum/plasma triglycerides (TG), high-density lipoprotein cholesterol (HDL), glucose, insulin and blood pressure. RESULTS: The sample consisted of 283 healthy men (age (mean+/-s.d.) 41.9+/-15.8 years; BMI, 26.0+/-3.2 kg/m(2); VAT, 2.7+/-1.8 L) and 411 women (age, 48.1+/-18.7 years; BMI 27.0+/-5.4 kg/m(2); VAT, 1.7+/-1.2 L). After adjusting for age, race, menopause status, scan position and specific blood analysis laboratory, VAT area at L(4)-L(5) had lower correlations with most metabolic risk factors including serum/plasma TG, HDL, glucose, insulin and blood pressure than VAT volume in both men and women. The VAT areas 10 and 15 cm above L(4)-L(5) in men had higher or equal correlations with health risk measures than VAT volume. In women, the VAT area 5 cm above or below L(4)-L(5) and total VAT volume had similar correlations with health risk measures. CONCLUSIONS: An appropriately selected single slice VAT area is an equally reliable phenotypic marker of obesity-related health risk as total VAT volume. However, in both men and women the VAT slice area at the traditional L(4)-L(5) level is not the best marker of obesity-related health risk.

Abdomen↗

PubMed2005

Low physical activity levels of modern Homo sapiens among free-ranging mammals.

Obesity prevalence rates are increasing worldwide and one prevailing hypothesis is that physical activity levels of modern humans are markedly reduced compared to those of our Paleolithic ancestors. We examine this hypothesis by deriving relative activity energy expenditure from available doubly labeled water and indirect calorimetry data in free-ranging non-human mammals. Our results, given the constraints posed by limited data availability, suggest that a low physical activity level, much less than that observed in free-ranging non-human mammals or highly active humans, is present in modern adult humans living within advanced settings. Our observations lend support to the hypothesis that low activity-related energy expenditure levels contribute to the rising worldwide prevalence of obesity.

Animals↗

PubMed2003

Is there an association between skeletal muscle mass and bone mineral density among African-American, Asian-American, and European-American women?

Skeletal muscle strength is a factor in the growth and maintenance of bone density and both skeletal muscle mass and bone mineral density are related to bone fracture risk. We studied the relationship between total body bone mineral density (TBBMD) and total appendicular skeletal muscle mass (TASM) estimated by dual-energy X-ray absorptiometry (DEXA) in African-American (AA), Asian-American (AsA), and European-American (EA) premenopausal (PRM) and postmenopausal (POM) women. The age- and weight-adjusted TBBMD-TASM association was positive in all PRM race groups and in POM EA, but was negative in POM AA and POM AsA. Body weight and age were positively and negatively associated with TBBMD, respectively, and the relationship was stronger in POM. In all race groups the variability in TBBMD was significantly greater in POM women.

Absorptiometry, Photon↗

PubMed2003

A novel soy-based meal replacement formula for weight loss among obese individuals: a randomized controlled clinical trial.

OBJECTIVE: To assess the efficacy and safety of a low calorie soy-based meal replacement program for the treatment of obesity. DESIGN: A 12-week prospective randomized controlled clinical trial. SETTING: Outpatient weight control research unit. SUBJECTS: One hundred obese (28<BMI<or=41 kg/m(2)) volunteers between the ages of 35 and 65 y. Seventy-four participants completed the trial. INTERVENTION: Participants were randomized to either the meal replacement treatment group (n=50; 240 g/day, 1200 kcal/day) or control group (n=50). Both groups at baseline received a single dietary counseling session and a pamphlet describing weight loss practices. MAIN OUTCOME MEASURES: Weight, body fat, serum lipid concentrations. RESULTS: : By intent-to-treat analysis, the treatment group lost significantly more weight than the control group (7.00 vs 2.90 kg; P<0.001) and had a greater change in total (22.5 vs 6.8 mg/dl; P=0.013) and LDL cholesterol (21.2 vs 7.1 mg/dl; P<0.009). Among completers only, the treatment group again lost more weight (7.1 kg; n=37 vs 2.9 kg; n=37; P=0.0001) and had a greater reduction in total cholesterol (26.1 mg/dl; n=37 vs 6.7 mg/dl; P=0.0012) and a greater change in LDL cholesterol (21.6 vs 5.5 mg/dl; P=0.0025). (For any given degree of weight loss, the reduction in LDL cholesterol was significantly greater in the treatment group.) Treatment was well tolerated and no serious side effects were detected. CONCLUSIONS: Use of this soy-based meal replacement formula was effective in lowering body weight, fat mass and in reducing LDL cholesterol beyond what could be expected given the weight lost.

Adult↗

PubMed2002

Sexual dimorphism in the energy content of weight change.

BACKGROUND: The energy content of weight change is assumed to be sex- and age-neutral at 3,500 kcal/pound or 32.2 MJ/kg. OBJECTIVES: As sexual dimorphism in body composition generally exists in mammals, the primary hypothesis advanced and tested was that the energy content of weight change differs between men and women. DESIGN: The energy content of 129 adult men and 287 women was measured by neutron activation analysis. Cross-sectional energy content prediction models were developed and then evaluated in two longitudinal samples: one that used the same methods in 26 obese women losing weight; and the other a compilation of 18 previously reported weight change-body composition studies. RESULTS: Multiple regression modeling identified weight, sex, age and height as total energy content predictor variables with significant sex x weight (P<0.001) and age x weight (P<0.001) interactions; total model r(2) and s.e.e. were 0.89 and 107.3 MJ, respectively. The model's predictive value was supported in both longitudinal evaluation samples. Model calculations using characteristics of representative adults gaining or losing weight suggested that the energy content of weight change in women (approximately 30.1-32.2 MJ/kg) is near to the classical value of 32.2 MJ/kg and that in men the value is substantially lower, approximately 21.8-23.8 MJ/kg. The predicted energy content of weight change increases by about 10% in older (age approximately 70 y) vs younger (approximately 35 y) men and women. CONCLUSIONS: Sexual dimorphism and age-dependency appears to exist in the estimated energy content of weight change and these observations have important clinical and research implications.

Adult↗

PubMed2001

Resting energy expenditure: systematic organization and critique of prediction methods.

There are many published methods for predicting resting energy expenditure (REE) from measured body 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 among these various 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 goal of clarifying prevailing ambiguities in the field. Our classification scheme is founded on body composition level (whole-body, tissue-organ, cellular, and molecular) and related components as the REE predictor variables. Each existing REE prediction method by body composition must belong to one body composition level. The suggested classification system, founded on a conceptual basis, highlights similarities and differences among the diverse REE-body composition prediction methods, provides a framework for teaching REE-body composition relationships, and identifies important future research opportunities.

Animals↗

PubMed2001

Is obesity a disease?

BACKGROUND: There is disagreement about whether obesity should be considered a disease, as can be seen by inconsistent usage and the advocacy of conflicting views in popular and scholarly articles. However, neither writers who refer to obesity as a disease nor those who question whether it is a disease have generally provided a definition of disease and then offered evidence that obesity does or does not fit the definition. METHOD: The characteristics of obesity were examined to determine whether they fit the common and recurring elements of definitions of disease taken from a sample of authoritative English language dictionaries. FINDINGS AND INTERPRETATIONS: Obesity, defined as a body mass index (BMI, kg/m(2)) or percentage body fat in excess of some cut-off value, though clearly a threat to health and longevity, lacks a universal concomitant group of symptoms or signs and the impairment of function which characterize disease according to traditional definitions. While it might nevertheless be possible to achieve a social consensus that it is a disease despite its failure to fit traditional models of disease, the merits of such a goal are questionable. Labeling obesity a disease may be expedient but it is not a necessary step in a campaign to combat obesity and it may be interpreted as self-serving advocacy without a sound scientific basis.

Body Mass Index↗

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

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↗

PubMed2000

Self-help weight loss versus a structured commercial program after 26 weeks: a randomized controlled study.

PURPOSE: There have been few randomized controlled trials of commercial weight-loss programs. This ongoing study compares the effects of a self-help program and a commercial program on weight loss and other measures of obesity in overweight and obese men and women. SUBJECTS AND METHODS: We report the results of the first 26 weeks of a multicenter, randomized, 2-year study of 423 subjects who had a body mass index of 27 to 40 kg/m(2). Subjects were randomly assigned to either a self-help program, consisting of two 20-minute sessions with a nutritionist and provision of printed materials and other self-help resources, or to attendance at meetings of a commercial program (Weight Watchers). Outcome measures were changes in body weight, body mass index, waist circumference, and body fat. Changes in serum homocysteine levels were measured in a subsample of participants during the first 12 weeks. RESULTS: After 26 weeks, subjects in the commercial program, as compared with those in the self-help program, had greater decreases in body weight [mean (+/- SD) -4.8+/-5.6 vs -1.4+/-4.7 kg] and body mass index (-1.7+/-1.9 vs -0.5+/-1.6 kg/m(2), both P<0.001) in intention-to-treat analyses. Among subjects measured at week 26, mean waist circumference (-4.3+/-10.5 vs -0.7+/-12.7 cm) and fat mass (-3.8 +/-7.0 vs -1.5+/-7.6 kg, both P<0.05) also decreased more among subjects in the commercial program. Mean serum homocysteine levels improved in the commercial program compared with self-help (-0.5+/-1.3 vs 0.9+/-1.8 microM, P<0.05). CONCLUSIONS: A structured commercial weight-loss program is more likely to be effective for managing moderately overweight patients than brief counseling and self-help.

Adult↗

PubMed2000

Weight stability masks sarcopenia in elderly men and women.

Skeletal muscle loss or sarcopenia in aging has been suggested in cross-sectional studies but has not been shown in elderly subjects using appropriate measurement techniques combined with a longitudinal study design. Longitudinal skeletal muscle mass changes after age 60 yr were investigated in independently living, healthy men (n = 24) and women (n = 54; mean age 73 yr) with a mean +/- SD follow-up time of 4.7 +/- 2.3 yr. Measurements included regional skeletal muscle mass, four additional lean components (fat-free body mass, body cell mass, total body water, and bone mineral), and total body fat. Total appendicular skeletal muscle (TSM) mass decreased in men (-0.8 +/- 1.2 kg, P = 0.002), consisting of leg skeletal muscle (LSM) loss (-0.7 +/- 0.8 kg, P = 0.001) and a trend toward loss of arm skeletal muscle (ASM; -0.2 +/- 0.4 kg, P = 0.06). In women, TSM mass decreased (-0.4 +/- 1.2 kg, P = 0.006) and consisted of LSM loss (-0.3 +/- 0.8 kg, P = 0.005) and a tendency for a loss of ASM (-0.1 +/- 0.6 kg, P = 0.20). Multiple regression modeling indicates greater rates of LSM loss in men. Body weight in men at follow-up did not change significantly (-0.5 +/- 3.0 kg, P = 0.44) and fat mass increased (+1.2 +/- 2.4 kg, P = 0.03). Body weight and fat mass in women were nonsignificantly reduced (-0.8 +/- 3.9 kg, P = 0.15 and -0.8 +/- 3.5 kg, P = 0.12). These observations suggest that sarcopenia is a progressive process, particularly in elderly men, and occurs even in healthy independently living older adults who may not manifest weight loss.

Absorptiometry, Photon↗

PubMed2000

Resting energy expenditure-fat-free mass relationship: new insights provided by body composition modeling.

The relationship between resting energy expenditure (REE) and metabolically active fat-free mass (FFM) is a cornerstone in the study of physiological aspects of body weight regulation and human energy requirements. Important questions, however, remain unanswered regarding the observed linear REE-FFM association in adult humans. This led us to develop a series of REE-body composition models that provide insights into the widely used simple linear REE-FFM prediction model derived experimentally in adult humans. The new models suggest that the REE-FFM relationship in mammals as a whole is curvilinear, that a segment of this function within a FFM range characteristic of adult humans can be fit with a linear equation almost identical to that observed from a composite review of earlier human studies, and that mammals as a whole exhibit a decrease in the proportion of FFM as high metabolic rate organs with greater FFM. The present study thus provides a new approach for examining REE-FFM relationships, advances in a quantitative manner previously observed albeit incompletely formulated REE-body composition associations, and identifies areas in need of additional research.

Algorithms↗

PubMed1999

Body composition in children and adults by air displacement plethysmography.

OBJECTIVES: Air displacement plethysmography (ADP) may provide a partial alternative to body density (Bd) and therefore body composition measurement compared to conventional hydrodensitometry (Hd) in children. As there are no evaluation studies of ADP in children, this study had a two-fold objective: to compare Bd estimates by ADP and Hd; and to compare fat estimates by both ADP and Hd to fat estimates by another reference method, dual energy X-ray absorptiometry (DXA). SETTING: Obesity Research Center, St. Luke's/Roosevelt Hospital, New York, USA. SUBJECTS: One hundred and twenty subjects (66 females/54 males) who ranged in age from 6-86 y and in body mass index (BMI, kg/m2) from 14.1-40.0 kg/m2 met study entry criteria. STUDY DESIGN: Cross-sectional study of healthy children (age < or = 19 y) and adult group for comparison to earlier studies. Each subject completed ADP, Hd, and DXA studies on the same day. Only subjects with subjectively-judged successful Hd studies were entered into the study cohort. RESULTS: There was a high correlation between Bd by ADP and Hd (Bd Hd = 0.11 + 0.896 x Bd ADP; r = 0.93, SEE = 0.008 g/cm3, P < 0.0001), although the regression line slope and intercept differed significantly from 1 and 0, respectively. Additional analyses localized a small-magnitude Bd bias in the child (n = 48) subgroup. Both ADP and Hd %fat estimates were highly correlated (r > 0.9, P < 0.0001) with %fat by DXA in child and adult subgroups. Bland-Altman analyses revealed no significant %fat bias by either ADP or Hd vs DXA in either children or adults, although a bias trend (P = 0.11) was detected in the child subgroup. CONCLUSION: With additional refinements, the air displacement plethysmography system has the potential of providing an accurate and practical method of quantifying body fat in children as it now does in adults.

Absorptiometry, Photon↗

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↗

PubMed1996

Assortative mating for relative weight: genetic implications.

Most work on the genetics of relative weight has not considered the role of assortative mating, i.e., mate selection based on similarity between mates. We investigated the extent to which engaged men and women in an archival longitudinal database were similar to each other in relative body weight prior to marriage and cohabitation. After controlling for age, a small but statistically significant mate correlation was found for relative weight (r=.13, p=.023), indicating some assortative mating. Furthermore, we examined whether mate similarity in relative weight prior to marriage predicts survival of the marriage. No significant effects were found. In sum, these results are consistent with those of other studies in suggesting that there is a small but significant intermate correlation for relative weight. However, they are unique in showing that these results cannot be explained on the basis of (a) cohabitation, (b) age similarity, or (c) selective survival of marriages between couples more similar in relative weight. The implications of these findings for heritability studies, linkage studies, and the estimation of shared environmental effects are discussed.

Adult↗

PubMed1996

Obesity and risk of gallstone development on a 1200 kcal/d (5025 Kj/d) regular food diet.

OBJECTIVE: Previous studies report a greatly increased risk of gallstone formation in obese persons during periods of caloric restriction on very low calorie formula diets. The aim of the present study was to assess the risk of gallstone development in moderately obese patients losing weight on a prescribed 1200 kcal/d (5025 Kj/d) regular food diet. DESIGN AND SUBJECTS: A consecutive sample of 70 men and women (body mass index > 25 kg/m2) (mean +/- SD, 28.9 +/- 2.8 kg/m2) responding to an announcement of an outpatient weight loss program in a major metropolitan research and teaching hospital were enrolled in a meal replacement program which prescribed 1200 kcal/d (5025 Kj/d) consisting of regular foods with approximately 20 g/d fat (15% of kcal) for 16 weeks. RESULTS: Participants who completed the study (n = 34) lost a mean of 5.1 +/- 3.6 kg (p < 0.001) (range, +2.7 kg to -12.5 kg; 6.7 +/- 5.0% of body weight, range +/-3.1% to -17.0%; 0.36 +/- 0.25 kg/week) with no clinically significant adverse effects. There were no discernible new gallstones as measured by ultrasonography during the study period. Liver enzyme blood concentrations did not change significantly after 16 weeks except for alkaline phosphatase, which decreased by 4.5 mu/l from a mean initial level of 72.7 mu/l (p < 0.05). CONCLUSION: Weight loss over 16 weeks on a 1200 kcal/d (5025 Kj/d) regular food/approx 20 g/d fat (15% of kcal) diet was not accompanied by a high rate of gallstone formation in moderately obese persons.

Adult↗

PubMed1995

Genetic, environmental, and phenotypic links between body mass index and blood pressure among women.

Greater relative weight is associated with higher blood pressure, but the reasons are unknown. The inability of current technology to induce sustained weight loss among overweight persons precludes experimental tests of whether this association is causal. We evaluated the degree to which the covariation between body mass index (BMI; kg/m2) and blood pressure (BP) among women is due to pleiotropic genetic factors, environmental factors, or phenotypic causation. The sample included 75 monozygotic (MZ) and 39 dizygotic (DZ) pairs of adult female twins. "BP" was calculated as the unit-weighted mean of systolic and diastolic. Data were analyzed through structural equation modeling. A model was specified stipulating that additive genetic effects (A) and unique environmental effects (E) each contributed to the covariance between BMI and BP, thus allowing for both pleiotropic and unique environmental influences on the covariance between BMI and BP. Dropping the pleiotropic influences significantly worsened the model (chi 2 = 4.62, df = 1, P = .032), suggesting significant pleiotropic effects. Dropping the environmental influences on the cross-phenotype covariance did not significantly worsen the model (chi 2 = 1.42, df = 1, P = .233). This indicates no significant effect of the environment on the covariance between BMI and BP. Finally, a model of phenotypic causation in which BMI directly influenced BP was fitted. This model provided the best single parameter explanation of the BP-BMI covariation. These data suggest that, among women, regardless of the source of variation, changes in BMI should lead to long-standing changes in BP.

Adult↗