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Biomedical subjects

Stanley Heshka

Publications and source records attributed to Stanley Heshka.

15 recordsLinked to original sources
PubMed2003

Weight loss with self-help compared with a structured commercial program: a randomized trial.

CONTEXT: Although commercial weight loss programs provide treatment to millions of clients, their efficacy has not been evaluated in rigorous long-term trials. OBJECTIVE: To compare weight loss and health benefits achieved and maintained through self-help weight loss vs with a structured commercial program. DESIGN AND SETTING: A 2-year, multicenter randomized clinical trial with clinic visits at 12, 26, 52, 78, and 104 weeks conducted at 6 academic research centers in the United States between January 1998 and January 2001. PARTICIPANTS: Overweight and obese men (n = 65) and women (n = 358) (body mass index, 27-40) aged 18 to 65 years. INTERVENTION: Random assignment to either a self-help program (n = 212) consisting of two 20-minute counseling sessions with a nutritionist and provision of self-help resources or to a commercial weight loss program (n = 211) consisting of a food plan, an activity plan, and a cognitive restructuring behavior modification plan, delivered at weekly meetings. MAIN OUTCOME MEASURES: Weight change was the primary outcome measure. Secondary outcomes included waist circumference, body mass index, blood pressure, serum lipids, glucose, and insulin levels. RESULTS: At 2 years, 150 participants (71%) in the commercial group and 159 (75%) in the self-help group completed the study. In the intent-to-treat analysis, mean (SD) weight loss of participants in the commercial group was greater than in the self-help group at 1 year (-4.3 [6.1] kg vs -1.3 [6.1] kg, respectively; P<.001) and at 2 years (-2.9 [6.5] kg vs -0.2 [6.5] kg, respectively; P<.001). Waist circumference (P =.003) and body mass index (P<.001) decreased more in the commercial group. Changes in blood pressure, lipids, glucose, and insulin levels were related to changes in weight in both groups, but between-group differences in biological parameters were mainly nonsignificant by year 2. CONCLUSION: The structured commercial weight loss program provided modest weight loss but more than self-help over a 2-year period.

Adult↗
PubMed2003

Recombinant variant of ciliary neurotrophic factor for weight loss in obese adults: a randomized, dose-ranging study.

CONTEXT: Obese individuals tend to resist the weight-regulating effects of exogenously administered leptin. A genetically engineered recombinant human variant ciliary neurotrophic factor (rhvCNTF) that signals through leptinlike pathways in the hypothalamus has been shown to bypass leptin resistance in animal models of obesity. OBJECTIVE: To identify a safe and well-tolerated dose of rhvCNTF that causes weight loss in obese adults. DESIGN, SETTING, AND PATIENTS: Twelve-week, double-blind, randomized, parallel-group, dose-ranging, multicenter clinical trial conducted at 2 university obesity clinics and at 5 independent clinical research clinics from March 2000 to August 2001, and including 173 nondiabetic obese adults, 82.6% of whom were women, with a mean (SD) body mass index of 41.1 (4.1). INTERVENTIONS: Patients were randomly assigned to receive daily for 12 weeks subcutaneous injections of placebo (n = 32) or 0.3 microg/kg (n = 32), 1.0 microg/kg (n = 38), or 2.0 microg/kg (n = 33) of rhvCNTF. Another group received 1.0 microg/kg for 8 weeks and placebo for 4 weeks (n = 38), but they were not included in the primary analysis. All participants received instructions for a reduced-calorie diet (World Health Organization formula minus 500 kcal/d). MAIN OUTCOME MEASURES: Change in weight during the 12-week double-blind treatment period and proportion of patients who achieved a weight loss of at least 5%. RESULTS: Of the 173 randomized patients, 123 (71%) completed the double-blind dosing period. Mean (SEM) changes in kilograms from baseline body weights were 0.1 (0.6) for placebo and -1.5 (0.6) for the 0.3, -4.1 (0.6) for the 1.0, and -3.4 (0.7) for the 2.0 microg/kg of rhvCNTF dosage groups (P<.001, test for trend). Two patients (8.7%) in the placebo and 2 (8.3%) in the 0.3- microg/kg, 8 (29.6%) in the 1.0- microg/kg, and 5 (26%) in the 2.0- microg/kg treatment groups achieved a weight loss of at least 5%. Recombinant human variant CNTF was generally well tolerated although adverse events occurred in 75% of patients receiving placebo and 78% to 93% of patients receiving rhvCNTF, in a dose-related fashion, with mild injection site reactions as the most frequently reported adverse event. CONCLUSIONS: In this initial, dose-ranging, 12-week study, treatment with rhvCNTF resulted in more weight loss than placebo. These preliminary findings require confirmation in large prospective clinical trials.

Adult↗
PubMed2003

The metabolic syndrome: prevalence and associated risk factor findings in the US population from the Third National Health and Nutrition Examination Survey, 1988-1994.

BACKGROUND: The metabolic syndrome is an important cluster of coronary heart disease risk factors with common insulin resistance. The extent to which the metabolic syndrome is associated with demographic and potentially modifiable lifestyle factors in the US population is unknown. METHODS: Metabolic syndrome-associated factors and prevalence, as defined by Adult Treatment Panel III criteria, were evaluated in a representative US sample of 3305 black, 3477 Mexican American, and 5581 white men and nonpregnant or lactating women aged 20 years and older who participated in the cross-sectional Third National Health and Nutrition Examination Survey. RESULTS: The metabolic syndrome was present in 22.8% and 22.6% of US men and women, respectively (P =.86). The age-specific prevalence was highest in Mexican Americans and lowest in blacks of both sexes. Ethnic differences persisted even after adjusting for age, body mass index, and socioeconomic status. The metabolic syndrome was present in 4.6%, 22.4%, and 59.6% of normal-weight, overweight, and obese men, respectively, and a similar distribution was observed in women. Older age, postmenopausal status, Mexican American ethnicity, higher body mass index, current smoking, low household income, high carbohydrate intake, no alcohol consumption, and physical inactivity were associated with increased odds of the metabolic syndrome. CONCLUSIONS: The metabolic syndrome is present in more than 20% of the US adult population; varies substantially by ethnicity even after adjusting for body mass index, age, socioeconomic status, and other predictor variables; and is associated with several potentially modifiable lifestyle factors. Identification and clinical management of this high-risk group is an important aspect of coronary heart disease prevention.

Adult↗
PubMed2003

Maternal-child feeding patterns and child body weight: findings from a population-based sample.

BACKGROUND: Certain mother-child feeding patterns (MCFPs) may promote childhood obesity and/or disordered eating. OBJECTIVES: To assess the demographic correlates of MCFPs and to test whether differences in MCFPs are associated with child body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters) z scores in a population-based study. DESIGN: A secondary analysis of the National Longitudinal Survey of Youth main and child cohorts was conducted on more than 1000 Hispanic, African American, and non-Hispanic/non-African American children, aged 3 to 6 years. The MCFPs were measured by means of 3 interview questions probing mother-allotted child food choice, child compliance during meals, and child obedience during meals. RESULTS: Mothers of non-Hispanic/non-African American children allotted greater food choice than mothers of African American or Hispanic children. Maternal BMI and other demographic measures were unrelated to MCFPs. The lowest levels of mother-allotted child food choice and child eating compliance were associated with reduced child BMI, with mean BMI z scores of -0.36 and -0.41, respectively. Effect sizes were small, however, and MCFPs did not discriminate children who were overweight or at risk for being overweight from children who were not (P>.05). CONCLUSIONS: Feeding strategies providing the least child food choice were associated with reduced child BMI. However, MCFPs did not relate to child overweight status.

Analysis of Variance↗
PubMed2003

Volume estimates by imaging methods: model comparisons with visible woman as the reference.

OBJECTIVE: To compare the accuracy of four volume estimation models to actual tissue and organ volumes measured in the visible woman. METHODS: Actual volumes were calculated from 1-mm-thick visible woman images that were segmented for five major components including subcutaneous and visceral adipose tissue across the 1730 available slices. Four available models resolved to two equations: truncated cone/truncated pyramid vs. two-column/parallel trapezium. Between-slice interval and initial slice were systematically varied when deriving component volumes using the two equations in four regions. RESULTS: For each compartment and each between-slice interval, the means of the two-column model were always the same as the corresponding reference volumes, whereas those of the truncated cone model were smaller than the reference volumes. Similarly, the coefficient variation for the two-column model was always smaller than for the truncated cone model. DISCUSSION: The equation based on the parallel trapezium and the two-column models is more accurate in estimating tissue volumes than the corresponding equation for truncated pyramid and truncated cone models. This finding has important implications for the volume calculations of imaging-based body compartments such as adipose tissue.

Anatomy↗
PubMed2003

Larger mass of high-metabolic-rate organs does not explain higher resting energy expenditure in children.

BACKGROUND: Children have a high resting energy expenditure (REE) relative to their body weight. The decline in REE during growth may be due to changes in body composition or to changes in the metabolic rate of individual organs and tissues. OBJECTIVES: The goals were to quantify body-composition components in children at the organ-tissue level in vivo and to determine whether the observed masses 1) account for the elevated REE in children and 2) account, when combined with specific organ-tissue metabolic constants, for children's REE. DESIGN: This was a cross-sectional evaluation of 15 children (aged 9.3 +/- 1.7 y) and 13 young adults (aged 26.0 +/- 1.8 y) with body mass indexes (in kg/m(2)) < 30. Magnetic resonance imaging-derived in vivo measures of brain, liver, kidney, heart, skeletal muscle, and adipose tissue were acquired. REE was measured by indirect calorimetry (REE(m)). Previously published organ-tissue metabolic rate constants were used to calculate whole-body REE (REE(c)). RESULTS: The proportion of adipose-tissue-free mass as liver (3.7 +/- 0.5% compared with 3.1 +/- 0.5%; P < 0.01) and brain (6.2 +/- 1.2% compared with 3.3 +/- 0.9%; P < 0.001) was significantly greater in children than in young adults. The addition of brain and liver mass significantly improved the model but did not eliminate the role of age. REE(c) with published metabolic coefficients underestimated REE(m) (REE(c) = 3869 +/- 615 kJ/d; REE(m) = 5119 +/- 769 kJ/d; P < 0.001) in children. CONCLUSION: The decline in REE during growth is likely due to both a decrease in the proportion of some of the more metabolically active organs and tissues and changes in the metabolic rate of individual organs and tissues.

Adolescent↗
PubMed2003

Total body potassium differs by sex and race across the adult age span.

BACKGROUND: Total body potassium (TBK) is an index of fat-free mass. Data describing changes in TBK in African American, Asian, or Hispanic populations have not been reported. OBJECTIVE: The aim was to investigate possible sex and racial differences in TBK in adults over an age range of 70 y. DESIGN: The study used longitudinal and cross-sectional data collected in a body-composition unit from 973 men and 1368 women of African American, Asian, white, and Hispanic race-ethnicity. Random coefficient models in which baseline weight and height were taken into account were applied to estimate sex-specific changes in TBK among the 4 racial-ethnic groups. RESULTS: The ages of 30 and 31 y were identified for women and men, respectively, as the cutoffs after which TBK began to decline. Both sexes had similar racial-ethnic patterns for expected mean TBK at the age cutoffs: African Americans had the highest value, followed by whites, Hispanics, and Asians. After the age cutoffs, the decline in TBK differed by race and sex. In women, African Americans showed the most rapid decline, whereas Asians had the lowest. In men, Hispanics had the most rapid decline in TBK, followed by African Americans, whites, and Asians. CONCLUSION: Significant sex and racial differences exist in the rate of change in TBK with age. Further studies are needed to explore the associations of declining TBK with health risks.

Adult↗
PubMed2003

Percentage body fat ranges associated with metabolic syndrome risk: results based on the third National Health and Nutrition Examination Survey (1988-1994).

BACKGROUND: Increasing attention has focused on the association between body fatness and related metabolic risk factors. The quantitative link between percentage body fat (%BF) and the risk of metabolic syndrome is unknown. OBJECTIVES: The objectives were to determine the risk [odds ratios (ORs)] of metabolic syndrome based on %BF in black and white men and women in the United States and to provide corresponding ranges of %BF associated with a risk equivalent to body mass index (BMI; in kg/m(2)). DESIGN: The subjects were participants in the third National Health and Nutrition Examination Survey and were divided into those with and without the metabolic syndrome. OR equations were derived from logistic regression models for %BF and BMI, with the 25th percentile in the study population as the reference. Ranges were developed by associating %BF with the equivalent risk of metabolic syndrome based on established BMI cutoffs. RESULTS: Four sets (men, women, black, and white) of OR curves were generated for %BF and for BMI by using data from 8259 adults. The ORs for metabolic syndrome were lower in blacks than in whites at any given %BF or BMI. The developed cutoffs for %BF differed between men and women but showed only small race and age effects. A simplified set of sex-specific %BF ranges for the risk of metabolic syndrome were developed. CONCLUSIONS: The risk of metabolic syndrome can be established from measured %BF by using either the developed OR curves or %BF thresholds at traditional BMI cutoffs. This information should prove useful in both clinical and research settings.

Adipose Tissue↗
PubMed2003

Magnitude and variation of fat-free mass density: a cellular-level body composition modeling study.

The mean density of fat-free mass (FFM) is remarkably stable at 1.10 g/cm(3) in healthy adult humans, and this stability is a cornerstone of the widely applied densitometry-based two-compartment model for estimating total body fat. At present, the usual means of exploring FFM density is by in vitro or in vivo experimental studies. The purpose of the present investigation was to develop a cellular-level body composition model that includes seven factors that determine FFM density. The model, when applied with available empirical coefficients, predicted an FFM density similar to that observed in vivo. An analysis of the seven model components indicates that the ratio of extracellular solids to total body water is a major determinant of individual variation in FFM density. The difference in FFM density across sex, race, and age groups was examined with the developed model. The present study thus provides a conceptual framework for the systematic study of FFM density in humans.

Adipose Tissue↗
PubMed2002

Trunk fat and blood pressure in children through puberty.

BACKGROUND: Fat distribution is well recognized as a cardiovascular risk factor in adults. The association between android fat distribution and cardiovascular risk factors, such as blood pressure (BP), was previously reported in an African-American and Caucasian pediatric population. The aim of the present study was to investigate the relationship between BP and body fat distribution in a large cross-sectional pediatric sample. The effects of race, sex, and puberty on this relationship were assessed. METHODS AND RESULTS: BP was measured in 920 healthy children and adolescents (African-American, Asian, and Caucasian, ages 5 to 18 years). Fat distribution was determined by skinfold thickness and dual-energy X-ray absorptiometry (DXA). Pubertal status was assessed by the criteria of Tanner. Regression analysis was used to explore the association between BP and fat distribution. Significant positive relationships between systolic and diastolic BP and trunk fat adjusted for total fat were seen in boys at all pubertal stages in all 3 races by both DXA and skinfold measurements. In girls, trunk fat was not a significant predictor of BP. CONCLUSIONS: Our results demonstrate a sex difference in the relationship between BP and trunk fat in that a significant positive relationship was present in boys only. These findings, based on 2 independent measures of fat distribution, may help identify the specific features of individuals at risk, allow earlier intervention, and suggest sex-specific determinants for BP.

Abdomen↗
PubMed2002

DXA: potential for creating a metabolic map of organ-tissue resting energy expenditure components.

OBJECTIVE: This study tested the hypothesis that tissue-organ components can be derived from DXA measurements, and in turn, resting energy expenditure (REE) can be calculated from the summed heat productions of DXA-estimated brain, skeletal muscle mass (SM), adipose tissue, bone, and residual mass (RM). RESEARCH METHODS AND PROCEDURES: Subjects were divided into five groups of adults <50 years of age. The specific metabolic rate of RM was developed in 13 Group I healthy subjects and a DXA-brain mass prediction formula in 52 Group II subjects. SM, adipose tissue, and bone models were developed based on earlier reports. The composite REE prediction model (REEp) was tested in 154 Group III subjects in whom REEp was compared with measured REE (REEm). Features of the developed model were determined in 94 normal-weight men and women (Group IV) and seven spinal cord injury patients and healthy matched controls (Group V). RESULTS: REEp and REEm in Group III were highly correlated (y = 0.85x + 233; r = 0.82, p < 0.001), and no bias was detected. Both REEm (mean +/- SD, 1,579 +/- 324 kcal/d) and REEp (1,585 +/- 316 kcal/d) were also highly correlated (r values = 0.85 to 0.98; p values < 0.001) and provided similar group values to REE estimated by the Harris-Benedict equations (1,597 +/- 279 kcal/d) and Wang's composite fat-free mass-based REE equation (1,547 +/- 248 kcal/d). New insights into the sources and distribution of REE were provided by analysis of the demonstration groups. DISCUSSION: This approach offers a new practical and educational opportunity to examine REE in subject groups using modeling strategies that reveal the magnitude and distribution of fundamental somatic heat-producing units.

Absorptiometry, Photon↗
PubMed2002

Waist circumference and obesity-associated risk factors among whites in the third National Health and Nutrition Examination Survey: clinical action thresholds.

BACKGROUND: Waist circumference (WC) is strongly linked to obesity-associated risks. However, currently proposed WC risk thresholds are not based on associations with obesity-related risk factors but rather with body mass index (BMI; in kg/m(2)). OBJECTIVE: The objective was to determine the relations of WC to obesity-associated risk factors in a representative sample of US whites and to derive comparable risk thresholds for WC and BMI. DESIGN: Data on 9019 white participants of the third National Health and Nutrition Examination Survey were divided into 2 groups according to the presence of >or= 1 of 4 obesity-associated risk factors: low HDL cholesterol, high LDL cholesterol, high blood pressure, and high glucose. Odds ratio (OR) equations were derived from logistic regression models for WC and BMI with the use of the 25th percentile in the study population as the reference. Receiver operating characteristic curves for identifying risk factors were computed for WC and BMI. RESULTS: At BMIs of 25 and 30, ORs were 1.19 (95% CI: 1.06, 1.35) and 2.37 (95% CI: 1.33, 4.22) for men and 1.56 (95% CI: 1.29, 1.91) and 3.16 (95% CI: 1.94, 5.28) for women, respectively. The corresponding ORs for WC were at 90 and 100 cm for men and at 83 and 93 cm for women. Minima on the receiver operating characteristic curves for men were at 96 cm for WC and at 26 for BMI and for women were at 86 cm for WC and 25 for BMI. CONCLUSION: WC is more closely linked to cardiovascular disease risk factors than is BMI.

Body Constitution↗
PubMed2002

Body-size dependence of resting energy expenditure can be attributed to nonenergetic homogeneity of fat-free mass.

An enduring enigma is why the ratio of resting energy expenditure (REE) to metabolically active tissue mass, expressed as the REE/fat-free mass (FFM) ratio, is greater in magnitude in subjects with a small FFM than it is in subjects with a large FFM. This study tested the hypothesis that a higher REE/FFM ratio in subjects with a small body mass and FFM can be explained by a larger proportion of FFM as high-metabolic-rate tissues compared with that observed in heavier subjects. REE was measured by indirect calorimetry, FFM by dual-energy X-ray absorptiometry (DEXA), and tissue/organ contributions to FFM by whole body magnetic resonance imaging (MRI) in healthy adults. Four tissue heat-producing contributions to FFM were evaluated, low-metabolic-rate fat-free adipose tissue (18.8 kJ/kg), skeletal muscle (54.4 kJ/kg), and bone (9.6 kJ/kg); and high-metabolic-rate residual mass (225.9 kJ/kg). Initial evaluations in 130 men and 159 women provided strong support for two key, developed models, one linking DEXA FFM with MRI FFM estimates and the other linking REE predicted from the four MRI-derived components with measured REE. There was an inverse association observed between measured REE/FFM and FFM (r(2) = 0.17, P < 0.001). Allometric models revealed a similar pattern of tissue change relative to body mass across males and females with greater proportional increases in fat-free adipose tissue and skeletal muscle than in FFM and a smaller proportional increase in residual mass than in FFM. When examined as a function of FFM, positive slopes were observed for skeletal muscle/FFM and pooled low-metabolic-rate components, and a negative slope for residual mass. Our linked REE-body composition models and associations strongly support the hypothesis that FFM varies systematically in the proportion of thermogenic components as a function of body mass and FFM. These observations have important implications for the interpretation of between-individual differences in REE expressed relative to metabolically active tissue mass.

Adult↗
PubMed2002

Sex and race differences in fat distribution among Asian, African-American, and Caucasian prepubertal children.

Sexual dimorphism in fat distribution is thought to emerge during puberty. Truncal or android body fat distribution is characteristic of adult males but is also recognized as a human cardiovascular risk factor. Race differences in truncal fat are clearly evident in adults and have been described in prepubertal children but not between Asians and other race groups. The aim of this study in African-American, Asian, and Caucasian prepubertal children was to evaluate sex differences and race differences in body fat distribution. Analysis of covariance was used to explore fat distribution in 358 prepubertal children (176 girls and 182 boys; 143 Asians, 95 African-Americans, and 120 Caucasians), measured by skinfold thickness and dual-energy x-ray absorptiometry (DXA) in a cross-sectional study. Extremity and gynoid fat masses were evaluated after adjustment for trunk or android fat, respectively, and for covariates including age, weight, height, and interactions. In Asian children, sex differences were present in models for gynoid fat by DXA only (P < 0.001), with girls having greater gynoid fat than boys. In African-American and Caucasian children, sex differences were present in models for extremity and gynoid fat masses, measured by both methods. Among girls, Asians had generally lower adjusted extremity and gynoid fat than Caucasians and African-Americans. Among boys, Asians had lower adjusted extremity fat by DXA than Caucasians (P < 0.01) but greater gynoid fat by skinfolds than African-Americans (P < 0.01). This study of prepubertal children demonstrates that: 1) sex differences in body fat distribution are present in prepubertal children but that the specific characteristics for Asians differ from African-Americans and Caucasians, and 2) differences in body fat distribution in Asian children, compared with African-Americans and Caucasians, are present but vary by sex. This comparison of African-American, Asian, and Caucasian prepubertal children suggests phenotypic differences. Additional studies are needed to explore the metabolic and health risk implications of these findings.

Abdomen↗