Biomedical subjects

Stanley Heshka

Publications and source records attributed to Stanley Heshka.

At least 37 records · Page 2Linked to original sources

PubMed2004

Intermuscular adipose tissue-free skeletal muscle mass: estimation by dual-energy X-ray absorptiometry in adults.

Skeletal muscle (SM) is a large and physiologically important compartment. Adipose tissue is found interspersed between and within SM groups and is referred to as intermuscular adipose tissue (IMAT). The study objective was to develop prediction models linking appendicular lean soft tissue (ALST) estimates by dual-energy X-ray absorptiometry (DXA) with whole body IMAT-free SM quantified by magnetic resonance imaging. ALST and total-body IMAT-free SM were evaluated in 270 healthy adults [body mass index (BMI) of <35 kg/m(2)]. The SM prediction models were then validated by the leave-one-out method and by application in a new group of subjects who varied in SM mass [anorexia nervosa (AN), n = 23; recreational athletes, n = 16; patients with acromegaly, n = 7]. ALST alone was highly correlated with whole body IMAT-free SM [model 1: R(2) = 0.96, standard error (SE) = 1.46 kg, P < 0.001]; age (model 2: R(2) = 0.97, SE = 1.38 kg, P < 0.001) and sex and race (model 3: R(2) = 0.97, SE = 1.06 kg, both P < 0.001) added significantly to the prediction models. All three models validated in the athletes and patients with acromegaly but significantly (P < 0.01-0.001) over-predicted SM in the AN group as a whole. However, model 1 was validated in AN patients with BMIs in the model-development group range (n = 11; BMI of >16 kg/m(2)) but not in those with a BMI of <16 kg/m(2) (n = 12). The DXA-based models are accurate for predicting IMAT-free SM in selected populations and thus provide a new opportunity for quantifying SM in physiological and epidemiological investigations.

Absorptiometry, Photon↗

PubMed2004

Lifestyle behaviors associated with lower risk of having the metabolic syndrome.

The metabolic syndrome is a cluster of risk factors that predisposes individuals to cardiovascular disease (CVD) and diabetes and is present in almost one fourth of adult Americans. Risk factors involved with the metabolic syndrome can be altered via modifiable lifestyle factors, such as diet, physical activity, and smoking and drinking habits. The objective of this study was to examine the extent to which these modifiable lifestyle behaviors are associated with the risk of having the metabolic syndrome. Data from the Third National Health and Nutrition Examination Survey (NHANES III), conducted between 1988 and 1994, were used to measure the risk of having the metabolic syndrome in healthy adult Americans who follow certain lifestyle behaviors, such as dietary practices, levels of physical activity, smoking and drinking habits. Low physical activity level, high carbohydrate (CHO) intake, and current smoking habits were all significantly associated with an increased risk of having the metabolic syndrome, even after adjusting for other related covariates. Relative to physically inactive subjects, being physically active was associated with lower odds ratio (OR) (0.36, confidence interval [CI] 0.21 to 0.68, P < .01) in overweight men and in normal weight (0.36, CI 0.18 to 0.70, P < .01) and overweight (0.61, CI 0.38 to 0.97, P < .05) women. Although the type of CHO could not be distinguished, relative to a high CHO diet, men having a low or moderate CHO intake had a lower risk of having the metabolic syndrome with respective ORs of 0.41 (CI 0.24 to 0.67, P < .01) and 0.44 (CI 0.25 to 0.77, P < .01); no effect of dietary CHO was observed in women. Moderate alcohol consumption was not significantly related to the risk of having the metabolic syndrome in men, but was associated with a lower OR in women (0.76, CI 0.61 to 0.95, P < .05). Regression models indicate a reduced risk of having the metabolic syndrome when selected low-risk lifestyle factors are present in combination, particularly in subjects with body mass index (BMI) < 30 kg/m(2). According to our cross-sectional logistic models, the risk of having the metabolic syndrome is substantially lower in individuals who are physically active, nonsmoking, have a relatively low CHO intake and moderate alcohol consumption, and who maintain a BMI in the non-obese range. These observations have potentially important value for public health recommendations.

Adult↗

PubMed2004

Combination of BMI and Waist Circumference for Identifying Cardiovascular Risk Factors in Whites.

OBJECTIVE: BMI (kilograms per meters squared) and waist circumference (WC) (measured in centimeters) are each associated with the risk of developing cardiovascular disease (CVD). Therefore, a combination of the two may be more effective in identifying subjects at risk than either alone. The present study sought to identify the combination of BMI and WC that has the strongest association with CVD risk factors in whites. RESEARCH METHODS AND PROCEDURES: Subjects were 8712 white men and women from the Third National Health and Nutrition Examination Survey. The optimal combination of BMI and WC was developed using logistic regression models with BMI and WC as predictors and CVD risk factors as outcomes. The combined measure of BMI and WC using current cut-off points was also examined. Sensitivity, specificity, and receiver operating characteristics curves were compared between the combined measures and BMI alone. RESULTS: For white men, the optimal combination of BMI and WC for identifying CVD risk factors was 0.68 x BMI + 0.32 x WC. This combination generated a score that better estimated the odds of having CVD risk factors than either alone. For white women, WC alone largely determined the likelihood of having CVD risks. The combination of BMI and WC using current cut-off points may provide an improved measure of CVD risk. Combined measures showed a higher sensitivity or a shorter distance in receiver operating characteristic curves in the identification of CVD risk factors. DISCUSSION: Combined measures of BMI and WC may provide a higher overall test performance for CVD risk factors and may be useful in some ethnic groups as an improved means of screening subjects for further evaluation in the clinical setting.

Body Constitution↗

PubMed2004

Sex-specific fat distribution is not linear across pubertal groups in a multiethnic study.

OBJECTIVE: To investigate sexual dimorphism and race differences in fat distribution (android/gynoid) before and during puberty. RESEARCH METHODS AND PROCEDURES: Fat distribution was measured by skinfold thickness and DXA in healthy African-American, Asian, and white subjects (n = 920), divided into pre-, early, and late pubertal groups. RESULTS: Gynoid fat masses adjusted for covariates were lower in late pubertal compared with prepubertal boys, but were not consistently greater in late pubertal compared with prepubertal girls. Progression of sex-specific fat distribution with increasing maturation was present in Asians only. Among African-American and white subjects, early pubertal boys had greater gynoid fat mass compared with the prepubertal group, whereas early pubertal girls had less gynoid fat mass compared with the prepubertal group. Sexual dimorphism in fat distribution was present in all pubertal groups, except among whites at early puberty. Among girls, Asians had lower gynoid fat than whites and African Americans in all pubertal groups. Among boys, Asians had less gynoid fat by DXA in early puberty and late puberty. DISCUSSION: Comparison among races demonstrated differences in sexual dimorphism and sex-specific fat distribution with progression in pubertal group. However, in all race groups, the fat distribution of late pubertal boys was more "male" or "android" than prepubertal boys, but late pubertal girls did not differ consistently from prepubertal girls. These findings suggested that the greater sexual dimorphism of fat distribution in late puberty compared with prepuberty may be attributable to larger changes in boys with smaller changes in girls.

Adipose Tissue↗

PubMed2004

Body-composition differences between African American and white women: relation to resting energy requirements.

BACKGROUND: Body composition differs between African American (AA) and white women, and the resting metabolic rate (RMR) is likely to be lower in AA women than in white women. OBJECTIVE: We tested 2 hypotheses: that AA women have a greater proportion of low-metabolic-rate skeletal muscle (SM) and bone than do white women and that between-race musculoskeletal differences are a function of body weight. DESIGN: Hypothesis 1 was tested by comparing SM, bone, adipose tissue, and high-metabolic-rate residual mass across 22 pairs of matched AA and white women. Magnetic resonance imaging and dual-energy X-ray absorptiometry were used to partition weight into 4 components, and RMR was both calculated from tissue-organ mass and measured. Hypothesis 2 was evaluated by measuring SM, bone, fat, and residual mass in 521 AA and white women with the use of dual-energy X-ray absorptiometry alone. RESULTS: Hypothesis 1: AA women had greater SM ( +/- SD group difference: 1.52 +/- 2.48 kg; P < 0.01) and musculoskeletal mass (1.72 +/- 2.66 kg; P < 0.01) than did white women. RMR calculated from body composition and measured RMR did not differ; RMR estimated by both approaches tended to be lower (approximately 160 kJ/d) in AA women than in white women. Hypothesis 2: SM was significantly correlated with weight, height, age, and race x weight interaction; greater SM in the AA women was a function of body weight. CONCLUSIONS: Lower RMRs in AA women than in white women are related to corresponding differences in the proportions of heat-producing tissues and organs, and these race-related body-composition differences increase as a function of body weight.

Adipose Tissue↗

PubMed2004

Visceral adipose tissue: relations between single-slice areas and total volume.

BACKGROUND: Visceral adipose tissue (VAT), which is linked with the metabolic consequences of obesity, is usually characterized by measuring VAT area at the L4-L5 vertebral interspace. However, the location of the slice with the strongest relation to VAT volume is not established. OBJECTIVE: We sought to investigate the relations between cross-sectional VAT areas at different anatomic locations and VAT volume in a large, diverse sample of healthy subjects. DESIGN: VAT volume was derived from slice areas taken at 5-cm intervals from magnetic resonance images in 121 healthy men [x +/- SD age: 41.9 +/- 15.8 y; body mass index (BMI; in kg/m(2)): 26.0 +/- 3.2; VAT: 2.7 +/- 1.8 L] and 198 healthy women (age: 48.1 +/- 18.7 y; BMI: 27.0 +/- 5.4; VAT: 1.7 +/- 1.2 L). Regression models were developed to identify the best single slice for estimating VAT volume. RESULTS: The VAT area 10 cm above L4-L5 (A(+10)) in men (R(2) = 0.932, P < 0.001) and 5 cm above L4-L5 (A(+5)) in women (R(2) = 0.945, P < 0.001) had the highest correlation with abdominal VAT. R(2) increased by only 3.8% in men and 0.5% in women with adjustment for age, race, scanning position, BMI, and waist circumference. Studies using A(+10) in men and A(+5) in women will require 14% and 9% fewer subjects, respectively, than those using slices at L4-L5 and will have equivalent power. CONCLUSION: Measurement of slice areas at A(+10) in men and A(+5) in women provides greater power for the detection of VAT volume differences than does measurement at L4-L5.

Abdomen↗

PubMed2004

Dual-energy x-ray absorptiometry-measured lean soft tissue mass: differing relation to body cell mass across the adult life span.

Lean soft tissue (LST) measured by dual-energy X-ray absorptiometry (DEXA) is used as a metabolic measure in aging research despite evidence of extracellular fluid expansion and a corresponding reduction in body cell mass (BCM) in older participants. We investigated the hypothesis that the fraction of LST as BCM is smaller with greater age. Men and women (n = 2043) had DEXA and 40K-counting for body potassium and BCM measured on the same day. Both BCM and LST were lower with greater age but the relative lowering was larger for BCM. A multiple linear regression model was fitted with BCM/LST as the dependent variable, and age, sex, and interaction terms as independent variables. Men had a mean BCM/LST greater (p < .001) than women; quadratic and cubic age terms were also significant or approached significance. Thus, the fraction of LST as BCM is smaller in older adults, a finding that has implications for the interpretation of DEXA results.

Absorptiometry, Photon↗

PubMed2004

Effect of calcium supplementation on weight and fat loss in women.

Data suggest that a diet deficient in calcium is associated with higher body weight and that augmenting calcium intake may reduce weight and fat gain or enhance loss. Our aim was to determine whether calcium supplementation during a weight loss intervention affects body fat or weight loss. Data were combined from three separate 25-wk randomized, double blind, placebo-controlled trials of 1000 mg/d calcium supplementation in 100 premenopausal and postmenopausal women. The primary outcome measures were change in body weight and fat mass adjusted for baseline values. There were no significant differences in body weight or fat mass change between the placebo and the calcium-supplemented groups in the pooled analysis (adjusted mean +/- SE; body weight, placebo -6.2 +/- 0.7 vs. Ca -7.0 +/- 0.7 kg; fat mass, placebo -4.5 +/- 0.6 vs. Ca -5.5 +/- 0.6 kg), and no significant interactions of calcium supplementation with menopausal/diet status. Analysis as separate trials also found no significant differences between the placebo and the calcium groups. Calcium supplementation did not significantly affect amount of weight or fat lost by women counseled to follow a moderately restricted diet for 25 wk. Nevertheless, the magnitude and direction of the differences for group means are consistent with a hypothesized small effect.

Adipose Tissue↗

PubMed2003

Results of soy-based meal replacement formula on weight, anthropometry, serum lipids & blood pressure during a 40-week clinical weight loss trial.

BACKGROUND: To evaluate the intermediate-term health outcomes associated with a soy-based meal replacement, and to compare the weight loss efficacy of two distinct patterns of caloric restriction. METHODS: Ninety overweight/obese (28 < BMI < or = 41 kg/m2) adults received a single session of dietary counseling and were randomized to either 12 weeks at 1200 kcal/day, 16 weeks at 1500 kcal/d and 12 weeks at 1800 kcal/d (i.e., the 12/15/18 diet group), or 28 weeks at 1500 kcal/d and 12 weeks at 1800 kcal/d (i.e., the 15/18 diet group). Weight, body fat, waist circumference, blood pressure and serum lipid concentrations were measured at 4-week intervals throughout the 40-week trial. RESULTS: Subjects in both treatments showed statistically significant improvements in outcomes. A regression model for weight change suggests that subjects with larger baseline weights tended to lose more weight and subjects in the 12/15/18 group tended to experience, on average, an additional 0.9 kg of weight loss compared with subjects in the 15/18 group. CONCLUSION: Both treatments using the soy-based meal replacement program were associated with significant and comparable weight loss and improvements on selected health variables.

Clinical Trial↗

PubMed2003

Body cell mass: model development and validation at the cellular level of body composition.

Existing models to estimate the metabolically active body cell mass (BCM) component in vivo remain incompletely developed. The classic Moore model is based on an assumed BCM potassium content of 120 mmol/kg. Our objectives were to develop an improved total body potassium (TBK)-independent BCM prediction model on the basis of an earlier model (Cohn SH, Vaswani AN, Yasumura S, Yuen K, and Ellis KJ. J Lab Clin Med 105: 305-311, 1985), to apply this improved model in subjects to explore the sex and age dependence of the TBK/BCM ratio, to develop a new TBK/BCM model on the basis of physiological associations between TBK and total body water (TBW) at the cellular level of body composition, and to fit this new model with available reference data. Subjects were 112 healthy adults who had the following components measured: TBW by 2H2O or 3H2O, extracellular water by NaBr, total body nitrogen by in vivo neutron activation, bone mineral by dual-energy X-ray absorptiometry, and TBK by whole body counting. Human reference data were collected from earlier published reports. The improved Cohn model-derived TBK/BCM ratio was (mean +/- SD) 109.0 +/- 10.9 mmol/kg and was not significantly related to sex and age. A simplified version of the new TBK-TBW model provided a TBK/BCM ratio almost identical (109.1 mmol/kg) to that derived by the improved Cohn model. The TBK-BCM prediction formula derived from the improved and new models [BCM (kg) = 1/109 x TBK (mmol); or BCM = 0.0092 x TBK] gives BCM estimates approximately 11% higher than the classic Moore model (BCM = 0.0083 x TBK) formulated on rough tissue composition estimates. The present analyses provide a physiologically based, improved, and validated TBK-BCM prediction formula that should prove useful in body composition and metabolism research.

Adult↗

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↗