Influence of body composition on bone mineral content in elderly women. A preliminary report.
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Absorptiometry, Photon↗
Biomedical subjects
A Pietrobelli
Publications and source records attributed to A Pietrobelli.
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↗
Weight loss increases and fat loss decreases all-cause mortality rate: results from two independent cohort studies.
OBJECTIVE: In epidemiological studies, weight loss is usually associated with increased mortality rate. Contrarily, among obese people, weight loss reduces other risk factors for disease and death. We hypothesised that this paradox could exist because weight is used as an implicit adiposity index. No study has considered the independent effects of weight loss and fat loss on mortality rate. We studied mortality rate as a function of weight loss and fat loss. DESIGN: Analysis of 'time to death' in two prospective population-based cohort studies, the Tecumseh Community Health Study (1890 subjects; 321 deaths within 16y of follow-up) and the Framingham Heart Study (2731 subjects; 507 deaths within 8y of follow-up), in which weight and fat (via skinfolds) loss were assessable. RESULTS: In both studies, regardless of the statistical approach, weight loss was associated with an increased, and fat loss with a decreased, mortality rate (P < 0.05). Each standard deviation (s.d.) of weight loss (4.6 kg in Tecumseh, 6.7 kg in Framingham) was estimated to increase the hazard rate by 29% (95% confidence interval CI), (14%, 47%, respectively) and 39% (95% CI, 25%, 54% respectively), in the two samples. Contrarily, each s.d. of fat loss (10.0 mm in Tecumseh, 4.8 mm in Framingham) was estimated to reduce the hazard rate 15% (95% CI, 4%, 25%) and 17% (95% CI, 8%, 25%) in Tecumseh and Framingham, respectively. Generalisability of these results to severely (that is, body mass index BMI) > or = 34) obese individuals is unclear. CONCLUSIONS: Among individuals that are not severely obese, weight loss is associated with increased mortality rate and fat loss with decreased mortality rate.
Adipose Tissue↗
An independent, inverse association of high-density-lipoprotein-cholesterol concentration with nonadipose body mass.
BACKGROUND: Increasing body mass index (BMI) is associated with progressively lower serum HDL-cholesterol concentrations, although the underlying body-composition compartment accounting for this unfavorable lipid change remains uncertain. OBJECTIVE: Because growing evidence favors a role of lean tissue in HDL homeostasis, the hypothesis was tested that non-adipose tissue components of body mass explain the inverse association of HDL cholesterol and BMI. DESIGN: Fasting serum lipid concentrations and body composition [total, subcutaneous, and visceral adipose tissue; adipose tissue-free mass (ATFM); and skeletal muscle by whole-body magnetic resonance imaging and body cell mass by 40K counting) were evaluated in healthy adults. Body-composition compartments were expressed as height2-normalized indexes. RESULTS: An inverse correlation was observed between serum HDL cholesterol and BMI in women (n = 68; R2 = 0.08, P = 0.023) and men (n = 61; R2 = 0.07, P = 0.046). Significant inverse correlations (P = 0.005-0.02) were also observed between HDL cholesterol and nonadipose components (ie, ATFM, skeletal muscle, and body cell mass) but not between HDL cholesterol and any adipose tissue component. The association between HDL cholesterol and ATFM remained significant after serum triacylglycerol was controlled for. When BMI was entered into the HDL cholesterol-ATFM regression model, BMI was not a significant independent variable. The strongest correlate of serum triacylglycerol was visceral adipose tissue (P = 0.002 for both women and men). CONCLUSIONS: Lean tissues and body cell mass appear to account in part for the long-observed inverse association of HDL cholesterol and BMI. These observations suggest a link between nonadipose tissue compartments and the greater cardiovascular risk associated with high BMI.
Adipose Tissue↗
Hydration of fat-free body mass: review and critique of a classic body-composition constant.
The assumed "constancy" of fat-free body mass hydration is a cornerstone in the body-composition research field. Hydration, the observed ratio of total body water to fat-free body mass, is stable at approximately 0.73 in mammals and this constancy provides a means of estimating total body fat in vivo. This review examines both in vitro and in vivo data that support the hydration constancy hypothesis and provides a critique of applied methodology. Biological topics of interest are then examined and critical areas in need of future research are identified. These are important issues because water dilution is the only method currently available for estimating body fat in all mammals, which range in body mass by a factor of 10(4).
Absorptiometry, Photon↗
The relationship between body composition and physical performance in older women.
BACKGROUND: The relationship between age-associated change in body composition and physical disability is still unknown. Skeletal muscle mass declines with age in both sexes; however, since women have less muscle mass per unit of weight than men, these changes may be more debilitating in women. OBJECTIVE: To evaluate the relationship between body composition and physical performance. DESIGN: A cross-sectional study. PARTICIPANTS: 144 women aged 68 to 75 were selected randomly from the general population of Verona. MEASUREMENTS: Body composition was evaluated using dual energy X-ray absorptiometry and bioimpedance. Physical performance was evaluated using a modified version of the Activities of Daily Living scale. Distance walked in 6 minutes was calculated, and isometric knee strength was tested. RESULTS: Normal women had a significantly lower body mass index (BMI) and percent body fat. These women also had a higher ratio of body cell mass (BCM) and total fat free mass (FFM) than women with physical impairments. After adjusting for BMI, women in the lowest tertile of muscle strength had significantly lower BCM than those in the highest tertile. CONCLUSIONS: These cross-sectional data show that although muscle strength is related to fat-free mass, disability in older women is associated with heavier BMI and with a higher percentage of body fat.
Absorptiometry, Photon↗
Hydration of fat-free body mass: new physiological modeling approach.
Water is an essential component of living organisms, and in adult mammals the fraction of fat-free body mass (FFM) as water is remarkably stable at approximately 0.73. The stability of FFM hydration is a cornerstone of the widely used water isotope dilution method of estimating total body fat. At present, the only suggested means of studying FFM hydration is by experimental total body water (TBW) and FFM measurements. Although deviations from the classical hydration constant are recognized, it is unknown if these are explainable physiological aberrations and/or methodological errors. Moreover, many questions related to hydration stability prevail, including body mass and age effects. These unresolved questions and the importance of the TBW-fat estimation method led us to develop a cellular level FFM hydration model. This physiological model reveals that four water-related ratios combine to produce the observed TBW-to-FFM ratio. The mean and range of FFM hydration observed in adult humans can be understood with the proposed physiological model as can variation in the TBW-to-FFM ratio over the human life span. An extension of the model to the tissue-organ body composition level confirms on a theoretical basis a small but systematic decrease in hydration observed in mammals ranging in body mass by a factor of 10(5). The present study, the first to advance a physiological hydration model, provides a conceptual framework for the TBW-fat estimation method and identifies important areas that remain to be studied.
Aging↗
Evidence for independent genetic influences on fat mass and body mass index in a pediatric twin sample.
OBJECTIVE: Insight into genetic and environmental influences on fat mass, independent of body mass index (BMI; kg/m2), is expected to enhance methods for treating pediatric obesity. However, few studies have estimated the heritability of fat mass in pediatric samples, and those conducted have relied primarily on BMI measurements. PRESENT STUDY: Using bioimpedance analysis, the present study tested a series of hypotheses predicting significant genetic and environmental influences on percent body fat (PBF) above and beyond BMI. Subjects were 66 pairs of twins, including 41 monozygotic and 25 dizygotic pairs, from 3 to 17 years of age. Structural equation modeling tested hypotheses, adjusting for demographic variables. RESULTS: Analyses indicated significant genetic influences on PBF, with genes estimated to account for 75% to 80% of the phenotypic variation. The remaining variation was attributable to nonshared environmental influences. Multivariate analyses revealed sizable genetic correlations and environmental correlations between BMI and PBF (rg =.74 and re =.67, respectively), suggesting that some genes and environmental experiences influence both phenotypes. However, analyses confirmed genetic and environmental influences on PBF above and beyond BMI. For example, 62.5% of the total genetic variation in PBF was attributable to genes that influenced PBF but not BMI. CONCLUSION: There seems to be a substantial genetic contribution to fat mass distinct from BMI in a sample of children and adolescents. Studies testing putative genetic or environmental determinants of pediatric obesity might be strengthened further by including research-based body composition methods.
Adipose Tissue↗
Nutrition and exercise in children with diabetes.
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Child↗
Childhood obesity: results of a multicenter study of obesity treatment in Italy.
The prevalence of pediatric obesity is increasing and many patients are followed by specialized centers or private doctors. The aim of this study was to verify short- and medium term results of a therapeutic approach based on nutritional intervention in a large pediatric population: 1383 subjects (695 females, 688 males) aged 10.1 +/- 2.7 yr, followed in 11 pediatric departments in Italy. No difference was found between centers in age, height, weight, BMI and IBW. The drop-out rate after the first visit was 30.2% (58.1% IBW > 140%) in females and 34.2% (70.7% IBW > 140%) in males. After two years of follow-up only 9.7% of females and 6.4% of males remained on treatment. Of these patients only 7.3% of females and 6.4% of males had IBW < 120%. These data show that an approach based on nutritional intervention alone is not sufficient for long-term treatment of pediatric obesity. Only an approach started early and involving the family can produce permanent results.
Adolescent↗
Garcinia cambogia (hydroxycitric acid) as a potential antiobesity agent: a randomized controlled trial.
CONTEXT: Hydroxycitric acid, the active ingredient in the herbal compound Garcinia cambogia, competitively inhibits the extramitochondrial enzyme adenosine triphosphate-citrate (pro-3S)-lyase. As a citrate cleavage enzyme that may play an essential role in de novo lipogenesis inhibition, G cambogia is claimed to lower body weight and reduce fat mass in humans. OBJECTIVE: To evaluate the efficacy of G cambogia for body weight and fat mass loss in overweight human subjects. DESIGN: Twelve-week randomized, double-blind, placebo-controlled trial. SETTING: Outpatient weight control research unit. PARTICIPANTS: Overweight men and women subjects (mean body mass index [weight in kilograms divided by the square of height in meters], approximately 32 kg/m2). INTERVENTION: Subjects were randomized to receive either active herbal compound (1500 mg of hydroxycitric acid per day) or placebo, and both groups were prescribed a high-fiber, low-energy diet. The treatment period was 12 weeks. Body weight was evaluated every other week and fat mass was measured at weeks 0 and 12. MAIN OUTCOME MEASURES: Body weight change and fat mass change. RESULTS: A total of 135 subjects were randomized to either active hydroxycitric acid (n = 66) or placebo (n = 69); 42 (64%) in the active hydroxycitric acid group and 42 (61%) in the placebo group completed 12 weeks of treatment (P = .74). Patients in both groups lost a significant amount of weight during the 12-week treatment period (P<.001); however, between-group weight loss differences were not statistically significant (mean [SD], 3.2 [3.3] kg vs 4.1 [3.9] kg; P = .14). There were no significant differences in estimated percentage of body fat mass loss between treatment groups, and the fraction of subject weight loss as fat was not influenced by treatment group. CONCLUSIONS: Garcinia cambogia failed to produce significant weight loss and fat mass loss beyond that observed with placebo.
Adult↗
Prader-Willi syndrome: relationship of adiposity to plasma leptin levels.
OBJECTIVE: Prader-Willi syndrome (PWS) is an autosomal dominant disorder involving the proximal long arm of chromosome 15, in which obesity is common. However, there is limited information on the underlying physiological mechanisms promoting obesity in this population. We tested whether there was a significant positive association between leptin and total body fat (TBF) in subjects with PWS, and whether this association was stronger among subjects with than without PWS. RESEARCH METHODS AND PROCEDURES: We studied 21 PWS patients and 64 non-PWS controls on whom we measured serum leptin, total body fat, glucose, insulin, and resting energy expenditure. We tested whether the slope of the regression line between leptin and TBF (in kg), measured by dual energy X-ray absorptiometry, was the same for PWS patients and non-PWS controls. RESULTS: Regression analyses indicated that the leptin-TBF association was significantly stronger among PWS patients. In contrast, the slope of the leptin-body mass index association did not significantly differ between PWS patients and non-PWS controls. None of the other outcome variables showed associations with leptin. DISCUSSION: Results suggest that the role of leptin in promoting obesity may be greater among subjects with PWS than among non-PWS controls.
Absorptiometry, Photon↗
Body mass index as a measure of adiposity among children and adolescents: a validation study.
OBJECTIVES: To test the hypothesis that in a healthy pediatric population body mass index (BMI) (kilograms per meter square) is a valid measure of fatness that is independent of age for both sexes. METHODS: Total body fat (TBF) (in kilograms) and percent of body weight as fat (PBF) were estimated by dual energy x-ray absorptiometry (DXA) in 198 healthy Italian children and adolescents between 5 and 19 years of age. We developed multiple regression analysis models with TBF and percent body fat as dependent variables and BMI, age, and interaction terms as independent variables. Separate analyses were conducted for boys and girls. RESULTS: BMI was strongly associated with TBF (R2 = 0.85 and 0.89 for boys and girls, respectively) and PBF (R2 =0.63 and 0.69 for boys and girls, respectively). Confidence limits on BMI-fatness association were wide, with individuals of similar BMI showing large differences in TBF and in PBF. Age was a significant covariate in all regression models. Addition of nonlinear terms for BMI did not substantially increase the R2 for TBF and PBF models in boys and girls. CONCLUSION: Our results support the use of BMI as a fatness measure in groups of children and adolescents, although interpretation should be cautious when comparing BMI across groups that differ in age or when predicting a specific individual's TBF or PBF.
Absorptiometry, Photon↗
Appendicular skeletal muscle mass: prediction from multiple frequency segmental bioimpedance analysis.
OBJECTIVES: Bioimpedance analysis (BIA) methods have potential to predict appendicular skeletal muscle mass (SM), although available 50 kHz prediction models include, in addition to impedance (Z), an independent age term. An age term in models is undesirable as it reflects incomplete understanding of underlying conduction physiology. This study tested the hypothesis, based on fluid distribution models related to aging, that appendicular SM bioimpedance analysis (BIA) prediction models would no longer include an independent age term, after first controlling for stature-adjusted appendicular impedance (height2/Z), at injected frequencies greater than 50 kHz. DESIGN: Cross-sectional evaluation of adults who had segmental Z and phase angle (phi) measured with multiple frequency BIA, and arm and leg SM with dual-energy X-ray absorptiometry (DXA). Skeletal muscle prediction models were developed with appendicular SM as dependent variable and height2/Z, gender, age and phi as potential independent variables. RESULTS: Examination of hypothesis in 49 subjects indicated: both arm and leg SM were highly correlated with height2/segmental Z at frequencies ranging from 1-300 kHz; gender was significant covariate in prediction models only at 1 kHz; age remained a significant covariate after controlling for height2/segmental Z at all frequencies; phi did not add significantly to models; and SM prediction models gave maximum R2 at 50 kHz for arm but R2 continued to rise up to 300 kHz for leg. CONCLUSION: Although multifrequency BIA did not eliminate SM prediction model age term, our findings suggest injected frequencies up to 300 kHz may have advantages for evaluating leg SM over conventional 50 kHz method.
Adult↗
Six-compartment body composition model: inter-method comparisons of total body fat measurement.
OBJECTIVE: To compare 16 currently used total body fat methods to a six-compartment criterion model based on in vivo neutron activation analysis. DESIGN: Observational, inter-method comparison study. SUBJECTS: Twenty-three healthy subjects (17 male and 6 female). MEASUREMENTS: Total body water (TBW) was measured by tritium dilution; body volume by underwater weighing (UWW); total body fat and bone mineral by dual-energy X-ray absorptiometry (DXA), total body potassium (TBK) by whole-body 40K counting; total body carbon, nitrogen, calcium, phosphorus, sodium and chlorine by in vivo neutron activation analysis; skinfolds/circumferences by anthropometry (Anth); and resistance by single-frequency bioimpedance analysis (BIA). RESULTS: The average of total body fat mass measurements by the six-compartment neutron activation model was 19.7+/-10.2kg (mean+/-s.d.) and comparable estimates by other methods ranged from 17.4-24.3 kg. Although all 16 methods were highly correlated with the six-compartment criterion model, three groups emerged based on their comparative characteristics (technical error, coefficient of reliability, Bland-Altman analysis) relative to criterion fat estimates, in decreasing order of agreement: 1. multi-compartment model methods of Baumgartner (19.5+/-9.9 kg), Heymsfield (19.6+/-9.9 kg), Selinger (19.7+/-10.2 kg) and Siri-3C (19.6+/-9.9 kg); 2. DXA (20.0+/-10.8 kg), Pace-TBW (18.8+/-10.1 kg), Siri-2C (20.0+/-9.9 kg), and Brozek-UWW (19.4+/-9.2 kg) methods; and 3. Segal-BIA (17.4+/-7.2 kg), Forbes-TBN (21.8+/-10.5 kg), Durnin-Anth (22.1+/-9.5 kg), Forbes-TBK (22.9+/-11.9 kg), and Steinkamp-Anth (24.3+/-9.5 kg) methods. CONCLUSION: Relative to criterion fat estimates, body composition methods can be organized into three groups based on inter-method comparisons including technical error, coefficient of reliability and Bland-Altman analysis. These initial groupings may prove useful in establishing the clinical and research role of the many available fat estimation methods.
Absorptiometry, Photon↗
Meta-analysis of the association of the Trp64Arg polymorphism in the beta3 adrenergic receptor with body mass index.
OBJECTIVE: As a result of efforts to isolate obesity-promoting genes, the Trp64Arg polymorphism in the beta3 adrenergic receptor locus, has been studied by many investigators. Results of the studies have varied in statistical significance and magnitude of the association of the polymorphism with body mass index (BMI: kg/m2). This has led to controversy about whether this polymorphism is associated with meaningful changes in BMI. To clarify the possible association, we conducted a meta-analysis. DESIGN: Meta-analytic study. MEASUREMENTS: For each genotype of the beta3 adrenergic receptor (Trp/Trp; Trp/Arg; Arg/Arg), we extracted the number of subjects, mean and standard deviation of BMI from 23 studies, including 36 different subgroups with a total of 7399 subjects. Other indices and obesity-related variables were not considered. RESULTS: No significant association of the Trp64Arg polymorphism with BMI was found. The weighted mean BMI difference between Trp/Trp homozygotes and Trp/Arg heterozygotes was 0.19 (s.e. = 0.11; P = 0.07). In addition, the distribution of effect sizes was not significantly heterogeneous (chi2=38.68; df 35; P = 0.31) suggesting that the variation of the effect sizes across the subgroups is not significant. A further weighted regression analysis, utilizing all three genotypes and adjusting for the random subgroup effect, also showed the effect of the polymorphism on BMI is not significant (F = 1.72, df = (2,54), P = 0.19). CONCLUSION: Based on existing data, the Trp64Arg polymorphism does not appear to be significantly associated with BMI. Moreover, we found no evidence for effect heterogeneity, suggesting that the effect of the polymorphism is not moderated by ethnicity or diabetic status.
Arginine↗
Techniques used in measuring human body composition.
Remarkable progress is evident in the field of body composition research. This review summarizes main body composition research concepts, examines new component measurement methodologies and identifies potential areas for future research. As the dual-energy X-ray absorptiometry is now gaining acceptance, both clinically and in the research laboratory, as a useful body composition method, particular emphasis is placed on this important approach.
Absorptiometry, Photon↗