Is percentage body fat differentially related to body mass index in Hispanic Americans, African Americans, and European Americans?

How well does the body adiposity index capture adiposity change in midlife women?: The SWAN fat patterning study

OBJECTIVES

The body adiposity index (BAI) is a proposed alternative to the body mass index (BMI) that has shown good cross-sectional agreement with percent body fat (%BF) in validation studies. The objective of this study was to examine the ability of BAI to track adiposity change over time in a biracial sample of midlife women.

METHODS

African-American (n = 159) and Caucasian (n = 206) women, aged 42-60 years, at the Chicago site of the Study of Women's Health Across the Nation were followed from 2002 to 2008. BAI and BMI were calculated from measurements taken at annual assessments. %BF was quantified using whole-body dual-energy X-ray absorptiometry. Difference scores (BAI(Δ) , BMI(Δ) , and %BF(Δ) ) quantified adiposity change over a mean of 1.6 (SD = 0.7) years. Lin's concordance correlation (ρ(c) ) and Bland-Altman limits-of-agreement assessed agreement between BAI and %BF.

RESULTS

In examining adiposity change, BAI(Δ) showed poor agreement with %BF(Δ) in the overall sample (ρ(c) = 0.41), African-American women (ρ(c) = 0.36), and Caucasian women (ρ(c) = 0.43). BAI(Δ) estimated %BF(Δ) with minimal bias (+0.4%) but low precision (±6.3%BF limits-of-agreement). %BF(Δ) had weaker correlations with BAI(Δ) (rs = 0.38-0.48) than with BMI(Δ) (rs = 0.48-0.59). BAI and BMI showed similar cross-sectional associations with %BF in the overall sample and within each race (rs > 0.74).

CONCLUSIONS

We conclude that BAI is less accurate than BMI in tracking adiposity change in midlife women, and would not be a suitable replacement for BMI in most research applications involving adiposity change.

Gestational weight gain as a predictor of longitudinal body mass index transitions among socioeconomically disadvantaged women

BACKGROUND

Socioeconomically disadvantaged women are at greater risk for gestational weight gain and postpartum weight retention compared to socioeconomically advantaged women. This study examines the effect of gestational weight gain on body mass index (BMI) transitions 5 years after pregnancy in socioeconomically disadvantaged women.

METHODS

Gestational weight gain was assessed in 2136 postpartum women participating in the Fragile Families and Child Well-being study who experienced full-term, singleton gestations. Longitudinal BMI transitions were defined as a change or stability in BMI category between two time points: BMI before the index pregnancy and BMI 5 years after the index pregnancy. Logistic regression models estimated the association between gestational weight gain and longitudinal BMI transitions, controlling for health before the index pregnancy, pregnancy history, and sociodemographic characteristics.

RESULTS

Excessive gestational weight gain was related to transitioning to a higher BMI category 5 years after the index pregnancy. Compared to white women, black and Hispanic women were more likely to transition or maintain a higher BMI category. Pregnancy history (i.e., parity at index pregnancy, interim pregnancy) and public assistance participation were associated with transitioning to a higher BMI category.

CONCLUSIONS

Among socioeconomically disadvantaged women, excessive gestational weight gain is related to transitioning to, but not maintaining, a higher weight category 5 years after the index pregnancy. Black and Hispanic women who are also socioeconomically disadvantaged and overweight or obese before conception may benefit from preconception or postpartum counseling about the long-term effect of gaining excessive weight during pregnancy and in the years immediately after childbirth.

Percentage of body fat cutoffs by sex, age, and race-ethnicity in the US adult population from NHANES 1999-2004

BACKGROUND

To date, there is no consensus regarding adult cutoffs of percentage of body fat or estimated cutoffs on the basis of nationally representative samples with rigorous body-composition measurements.

OBJECTIVE

We developed cutoffs of percentage of body fat on the basis of the relation between dual-energy x-ray absorptiometry-measured fat mass and BMI (in kg/m(2)) stratified by sex, age, and race-ethnicity by using 1999-2004 NHANES data.

DESIGN

A simple regression (percentage of body fat = β(0) + β(1) × 1 ÷ BMI) was fit for each combination of sex (men and women), 3 age groups (18-29, 30-49, and 50-84 y of age), and 3 race-ethnicity groups (non-Hispanic whites, non-Hispanic blacks, and Mexican Americans). Model fitting included a consideration of complex survey design and multiple imputations. Cutoffs of percentage of body fat were computed that corresponded to BMI cutoffs of 18.5, 25, 30, 35, and 40 on the basis of estimated prediction equations.

RESULTS

R(2) ranged from 0.54 to 0.72 for men (n = 6544) and 0.58 to 0.79 for women (n = 6362). In men, the percentage of body fat that corresponded to a BMI of 18.5, 25, 30, 35, and 40 across age and racial-ethnic groups ranged from 12.2% to 19.0%, 22.6% to 28.0%, 27.5% to 32.3%, 31.0% to 35.3%, and 33.6% to 37.6%, respectively; the corresponding ranges in women were from 24.6% to 32.3%, 35.0% to 40.2%, 39.9% to 44.1%, 43.4% to 47.1%, and 46.1% to 49.4%, respectively. The oldest age group had the highest cutoffs of percentage of body fat. Non-Hispanic blacks had the lowest cutoffs of percentage of body fat. Cutoffs of percentage of body fat were higher in women than in men.

CONCLUSIONS

Cutoffs of percentage of body fat that correspond to the current US BMI cutoffs are a function of sex, age, and race-ethnicity. These factors should be taken into account when considering the appropriateness of levels of percentage of body fat.

Analysis of body composition methods in a community sample of African American women

The purposes of the authors in this study were: (1) to determine whether published body mass index and bioelectrical impedance analysis equations agreed with dual energy x-ray absorptiometry body fat percentage measures and (2) to estimate new body mass index and bioelectrical impedance analysis equations in a sample of African American women. Linear regression was used to determine how well 10 body mass index and bioelectrical impedance analysis equations reflected dual energy x-ray absorptiometry body fat percentage measures in this sample of 74 African American women; new body mass index and bioelectrical impedance analysis equations were created using dual energy x-ray absorptiometry body fat percentage measures as the dependent variable. Participants (M = 47.6 years, SD = 7.7) were classified as overweight or obese (BMI Mean BF% = 35.4, SD = 8.2; BIA Mean BF% = 43.3, SD = 6.9; DXA Mean BF% = 41.5, SD = 6.1). R(2) and SEE values indicated that all body mass index and bioelectrical impedance analysis equations were a poorer fit with less precision, and the new bioelectrical impedance analysis equation discussed in this article was a better fit and was more precise. All 10 body mass index and bioelectrical analysis equations inaccurately estimated dual energy x-ray absorptiometry body fat percentage measures in our sample. The new body mass index equation discussed in this article had less estimation bias and more precision than the published body mass index equations and may be a more accurate equation in African American women.

Comparison of fat-free mass in super obesity (BMI ≥ 50 kg/m2) and morbid obesity (BMI <50 kg/m2) in response to different weight loss surgeries

BACKGROUND

Differences in excess weight loss, body mass index (BMI) change, and body composition have been related to different types of bariatric procedures. Our objective was to explore these alterations related to body mass in superobese (SO) and morbidly obese (MO) patients in a university hospital setting.

METHODS

Patients provided written informed consent and had their body composition measured before and after surgery using bioimpedance (Tanita 310). The t test was used to compare MO and SO. Pearson's correlations were used to examine the BMI, excessive BMI loss, percentage of body fat (BF) change, and fat-free mass.

RESULTS

A total of 133 MO patients had a BMI of 43.3 kg/m(2) and 88 SO patients had a BMI of 59.4 kg/m(2). The percentage of BF was 46.7% and 51.9% (P < .0001). The differences in the follow-up period after surgery (21.5 and 20.6 months; P = .62) and patient age (43.4 and 42.5 yr) were not significant, but the gender distribution was significant (P = .003). After surgery, the MO patients had a BMI of 30.9 ± 5.7 kg/m(2) and the SO patients had a BMI of 37.3 ± 9.0 kg/m(2). The percentage of BF was not different between the 2 groups (MO, 33.1% ± 9.6% and SO, 35.0% ± 12.4%; P = .21). Gender differences in the percentage of BF were present before surgery; however, after surgery, these were absent for the men in the 2 groups (24.8% and 26.6%; P = .51). The change in the BMI and the change in the BF had a stronger correlation for the MO patients (r = .83 versus r = .53) than for the SO patients. The fat-free mass loss correlated with the change in BMI without regard to procedure. The percentage of excessive BMI loss was 65.1% for the MO and 63.4% for the SO patients (P = .64).

CONCLUSIONS

The SO patients achieved excessive BMI loss similar to that of the MO patients, with more SO men choosing biliopancreatic diversion/duodenal switch. At a BMI of 37.3 kg/m(2), the SO patients had a percentage of BF that was not different from that of the MO patients at 30.9 kg/m(2). The fat-free mass losses correlated with the change in BMI.

Instrument selection for randomized controlled trials: why this and not that?

A fundamental linchpin for obtaining rigorous findings in quantitative research involves the selection of survey instruments. Psychometric recommendations are available for the processes for scale development and testing and guidance for selection of established scales. These processes are necessary to address the validity link between the phenomena under investigation, the empirical measures and, ultimately, the theoretical ties between these and the world views of the participants. Detailed information is most often provided about study design and protocols, but far less frequently is a detailed theoretical explanation provided for why specific instruments are chosen. Guidance to inform choices is often difficult to find when scales are needed for specific cultural, ethnic, or racial groups. This paper details the rationale underlying instrument selection for measurement of the major processes (intervention, mediator and moderator variables, outcome variables) in an ongoing study of postpartum Latinas, Madres para la Salud [Mothers for Health]. The rationale underpinning our choices includes a discussion of alternatives, when appropriate. These exemplars may provide direction for other intervention researchers who are working with specific cultural, racial, or ethnic groups or for other investigators who are seeking to select the 'best' instrument. Thoughtful consideration of measurement and articulation of the rationale underlying our choices facilitates the maintenance of rigor within the study design and improves our ability to assess study outcomes.

Inverted BMI rather than BMI is a better proxy for percentage of body fat

BACKGROUND

Percentage of body fat (BF%) is a known risk factor for a range of healthcare problems but is difficult to measure. An easy to measure proxy is the weight/height(2) ratio known as the Body Mass Index (BMI kg/m(2)). However, BMI does have some inherent weaknesses which are readily overcome by its inverse iBMI (1000/BMI, cm(2)/kg).

METHODS

The association between BF% and both BMI and iBMI together with their distributional properties was explored using previously published data from healthy (n = 2993) and diseased populations (n = 298).

RESULTS

BMI is skewed whereas iBMI is symmetrical and so is better approximated by the normal distribution. The relationship between BF% and BMI is curved, but that of iBMI and BF% is linear and thus iBMI explains more of the variation in BF% than BMI. For example a unit increase in BMI for a group of thin women represents an increase of 2.3% in BF, but for obese women this represents only a 0.3% increase in BF-a 7-fold difference. The curvature stems from body mass being the numerator in BMI but the denominator in BF% resulting in a form of hyperbolic curve which is not the case with iBMI. Furthermore, BMI and iBMI have different relationships (interaction) with BF% for men and women, but these differences are less marked with iBMI.

CONCLUSIONS

Overall, these characteristics of iBMI favour its use over BMI, especially in statistical models.

Ethnic differences in the relationship between body mass index and percentage body fat among Asian children from different backgrounds

Overweight and obesity in Asian children are increasing at an alarming rate; therefore a better understanding of the relationship between BMI and percentage body fat (%BF) in this population is important. A total of 1039 children aged 8-10 years, encompassing a wide BMI range, were recruited from China, Lebanon, Malaysia, The Philippines and Thailand. Body composition was determined using the 2H dilution technique to quantify total body water and subsequently fat mass, fat-free mass and %BF. Ethnic differences in the BMI-%BF relationship were found; for example, %BF in Filipino boys was approximately 2 % lower than in their Thai and Malay counterparts. In contrast, Thai girls had approximately 2.0 % higher %BF values than in their Chinese, Lebanese, Filipino and Malay counterparts at a given BMI. However, the ethnic difference in the BMI-%BF relationship varied by BMI. Compared with Caucasian children of the same age, Asian children had 3-6 units lower BMI at a given %BF. Approximately one-third of the obese Asian children (%BF above 25 % for boys and above 30 % for girls) in the study were not identified using the WHO classification and more than half using the International Obesity Task Force classification. Use of the Chinese classification increased the sensitivity. Results confirmed the necessity to consider ethnic differences in body composition when developing BMI cut-points and other obesity criteria in Asian children.

Generalized equations for estimating DXA percent fat of diverse young women and men: the TIGER study

PURPOSE

Popular generalized equations for estimating percent body fat (BF%) developed with cross-sectional data are biased when applied to racially/ethnically diverse populations. We developed accurate anthropometric models to estimate dual-energy x-ray absorptiometry BF% (DXA-BF%) that can be generalized to ethnically diverse young adults in both cross-sectional and longitudinal field settings.

METHODS

This longitudinal study enrolled 705 women and 428 men (aged 17-35 yr) for 30 wk of exercise training (3 d·wk(-1) for 30 min·d(-1) of 65%-85% predicted V˙O2max). The distribution of ethnicity was as follows: 37% non-Hispanic white, 29% Hispanic, and 34% African-American. DXA-BF%, skinfold thicknesses, and body mass index (BMI) were collected at baseline and after 15 and 30 wk.

RESULTS

Skinfolds, BMI, and race/ethnicity were significant predictors of DXA-BF% in linear mixed model regression analysis. For comparable anthropometric measures (e.g., BMI), DXA-BF% was lower in African-American women and men but higher in Hispanic women compared with non-Hispanic white. Addition of BMI to the skinfold model improved the SEE for women (3.6% vs 4.0%), whereas BMI did not improve prediction accuracy of men (SEE = 3.1%).

CONCLUSIONS

These equations provide accurate predictions of DXA-BF% for diverse young women and men in both cross-sectional and longitudinal settings. To our knowledge, these are the first published body composition equations with generalizability to multiple time points, and the SEE estimates are among the lowest published in the literature.

African genetic admixture is associated with body composition and fat distribution in a cross-sectional study of children

OBJECTIVE

Although differences in body composition parameters among African American (AA), Hispanic American (HA) and European American (EA) children are well documented, the factors underlying these differences are not completely understood. Environmental and genetic contributors have been evaluated as contributors to observed differences. This study evaluated the extent to which African or European ancestral genetic background influenced body composition and fat distribution in 301 peripubertal AA (n = 107), HA (n = 79) and EA (n = 115) children aged 7-12.

DESIGN

Estimates of African admixture (AFADM) and European admixture (EUADM) were obtained for every subject using 142 ancestry informative DNA markers. Dual energy X-ray absorptiometry and computed tomography scanning were used to determine body composition and abdominal fat distribution, respectively. Multiple regression models were conducted to evaluate the contribution of admixture estimates to body composition and fat distribution.

RESULTS

Greater AFADM was associated with lower fat mass (P = 0.0163), lower total abdominal adipose tissue (P = 0.0006), lower intra-abdominal adipose tissue (P = 0.0035), lower subcutaneous abdominal adipose tissue (P = 0.0115) and higher bone mineral content (BMC) (P = 0.0253), after adjusting for socio-economic status, sex, age, height, race/ethnicity and pubertal status. Greater EUADM was associated with lower lean mass (LM) (P = 0.0056).

CONCLUSION

These results demonstrate that ancestral genetic background contributes to racial/ethnic differences in body composition above and beyond the effects of racial/ethnic classification and suggest a genetic contribution to total body fat accumulation, abdominal adiposity, LM and BMC.

Drug disposition in obesity and protein–energy malnutrition

Clinical response to medication can differ between patients. Among the known sources of variability is an individual's nutrition status. This review defines some pharmacokinetic terms, provides relevant body size metrics and describes the physiologic influences of protein–energy malnutrition and obesity on drug disposition. Weight-based drug dosing, which presumes a healthy BMI, can be problematic in the protein–energy malnourished or obese patient. The use of total body weight, lean body weight, or an adjusted body weight depends on the drug and how it is differently handled in malnutrition or obesity. Most of the recognized influences are seen in drug distribution and drug elimination as a result of altered body composition and function. Distribution characteristics of each drug are determined by several drug-related factors (e.g. tissue affinity) in combination with body-related factors (e.g. composition). Drug elimination occurs through metabolic and excretory pathways that can also vary with body composition. The current data are limited to select drugs that have been reported in small studies or case reports. In the meantime, a rational approach to evaluate the potential influences of malnutrition and obesity can be used clinically based on available information. Antimicrobials are discussed as a useful example of this approach. Further advancement in this field would require collaboration between experts in body composition and those in drug disposition. Until more data are available, routine monitoring by the clinician of the protein–energy malnourished or obese patient receiving weight-based drug regimens is necessary.

Cultural considerations in the care of children with spina bifida

Spina bifida occurs when the neural tube fails to close during early fetal development, resulting in a range of neural tube defects (NTDs). The cause of spina bifida is not fully understood, but scientists believe that NTDs are the result of genetic and environmental factors acting simultaneously. The Centers for Disease Control reports that spina bifida and other NTDs occur more frequently in some ethnic groups, such as Hispanic people, than in others. The United States is increasingly multicultural and diverse, and it is becoming more difficult to categorize individuals into a single racial/ethnic group. This article uses the term ethnicity as defined by the Institute of Medicine and avoids using race unless part of a particular study.

Accuracy of current body mass index obesity classification for white, black, and Hispanic reproductive-age women

OBJECTIVE

To compare the National Institutes of Health's (NIH) body mass index (BMI)-based classification to identify obesity in comparison with the World Health Organization (WHO), which uses percent body fat, among white, black, and Hispanic reproductive-aged women.

METHODS

Body weight, height, BMI, and percent body fat (dual-energy X-ray absorptiometry generated) were determined for 555 healthy adult women aged 20-33 years (mean+/-standard deviation 26.5+/-4.0 years). Diagnostic accuracy of the NIH-based obesity definition (BMI of 30 kg/m or higher) was determined using the WHO criterion standard (percent body fat greater than 35%).

RESULTS

Obesity as defined by the NIH (BMI 30 kg/m or higher) and by WHO (percent body fat greater than 35%) classified 205 (36.9%) and 350 (63.1%) of the women as obese, respectively. The NIH-defined obesity cutoff values had 47.8%, 75.0%, and 53.9% sensitivity in white, black and Hispanic, women, respectively. White and Hispanic women had 2.9% greater percent body fat than black women for a given BMI. Receiver operating characteristics curves analyses showed that the respective sensitivities improved to 85.6%, 81.3%, and 83.2%, and that 311 women (56.0%) were classified as obese as a whole when race or ethnic-specific BMI cutoff values driven by our data (BMI at or above 25.5, 28.7, and 26.2 kg/m for white, black, and Hispanic women, respectively) were used to detect percent body fat-defined obesity.

CONCLUSION

Current BMI cutoff values recommended by the NIH failed to identify nearly half of reproductive-aged women who met the criteria for obesity by percent body fat. Using race or ethnic-specific BMI cutoff values would more accurately identify obesity in this population than the existing classification system.

Nutritional status and socioeconomic change among Toba and Wichí populations of the Argentinean Chaco

The prevalence of overweight and obesity is growing at an accelerated pace in disadvantaged populations. Indigenous populations all over the world, whose lifestyle is changing rapidly and drastically, seem to be particularly prone to show an increased prevalence of overweight and its co-morbidities among adults. The aim of this study was to evaluate the association between socioeconomic and nutritional statuses in adults of two indigenous populations of the Argentine Gran Chaco: the Toba and Wichí of the province of Formosa. Originally hunter-gatherers, they are now more settled and engage in temporary wage labor and local political positions. A total of 541 adults (>20 years old) participated in the study. Almost 50% of the adult Toba and 34% of the adult Wichí were overweight and 10% of adults in both populations were obese. Socioeconomic status was positively associated with body mass index in both populations. Furthermore, political connectedness with the non-indigenous sector, as in the case of community leaders, was highly correlated with obesity. Differences within and between groups can be explained by biocultural factors that include gender, diet (foraged vs store-bought), lifestyle (sedentary vs more active), and history of political power. Our study highlights the interactions among social, cultural, and political economic variables, such as political hierarchies within the group or degree of social connectedness with community leaders. By making these variables an integral part of our analysis and interpretation, we hope to improve our understanding of the situation of indigenous populations in transition.

Body size and risk of prostate cancer in Jamaican men

We investigated the associations between body size and risk of prostate cancer in a hospital-based case-control study in Jamaica. Height, weight, waist, and hip circumference were measured at enrollment, and data collected on medical and lifestyle factors for newly diagnosed cases (n = 243) and controls (n = 275). Compared with men in the normal range of waist-hip ratio (WHR), men with WHR > or =0.95 were at greater risk of total prostate cancer (OR,1.72; CI, 1.01-3.00) and high-grade cancer (OR, 2.02; CI, 1.03-3.96). With additional control for BMI, the association with WHR remained significant for total prostate cancer (OR, 1.90; CI, 1.01-3.53) and high-grade disease (OR, 2.94; CI, 1.34-6.38). There was no association between waist circumference and cancer without control for BMI but after controlling for BMI, waist circumference >90 cm (OR, 2.45; CI, 1.01-5.94) and >102 cm (OR, 5.57; CI, 1.43-18.63) showed a dose-response relationship with high-grade disease. Height and BMI were not associated with risk of prostate cancer. Abdominal obesity may be associated with risk of high-grade prostate cancer. Risk may be greater in those with higher abdominal obesity relative to overall size. The results further highlight the importance of investigating relationships by characteristics of the tumor.

Elderly Mexicans have less muscle and greater total and truncal fat compared to African-Americans and Caucasians with the same BMI

BACKGROUND

How body composition, specifically skeletal muscle mass, compares in Mexican elderly to other ethnic groups has not previously been reported. We tested the hypothesis that older adults from Northwest Mexico (Mex) would have similar total appendicular skeletal muscle (TASM) compared with New York dwelling Caucasians (Cauc) and African-Americans (AA).

METHODS

Two hundred and eighty nine Mex (135 males and 154 females), 166 AA (36 males and 130 females) and 229 Cauc (64 males and 165 females), aged 60-98 years were assessed. Total and regional fat and lean tissues were measured by whole-body dual energy X-ray absorptiometry where TASM is the sum of arm and leg bone-free and fat-free lean tissue. Differences in TASM were tested by ANCOVA, with age, height, and body mass index (BMI) as covariates.

RESULTS

TASM adjusted for ethnicity, age, height and BMI, were 22.6 +/- 0.2 kg and 17.8 +/- 0.1 kg for males and females, respectively (p < 0.001). Among males with similar age, height, and BMI, Mex had less TASM compared with AA and Cauc (p < 0.001). Total body fat and truncal fat were higher (p < 0.001) and FFM lower (p < 0.001) in Mex compared to both AA and Cauc males after adjusting for age and BMI. Among females, Mex had higher total and truncal fat (p < 0.001) after adjusting for age and BMI, and significantly lower TASM (p < 0.001) after adjusting for age, height, and BMI compared to AA and Cauc females.

CONCLUSIONS

Elderly Mex have a different body composition compared with AA and Cauc of a similar BMI and age. Mex have significantly less TASM with greater total and truncal fat. In the long-term, Mex elderly may be at greater risk for sarcopenic obesity compared to other ethnic groups.

Idiopathic intracranial hypertension is associated with lower body adiposity

OBJECTIVE

To characterize the obesity phenotype(s) in patients with idiopathic intracranial hypertension (IIH).

DESIGN

Database study.

PARTICIPANTS

We studied 44 consecutive patients with IIH, in addition to 184 women attending the obesity clinic of the same medical center and 199 obese women participating in the first Israeli national survey on health and nutrition conducted in 1999 and 2000.

METHODS

Anthropometric parameters were compared with those of 2 control groups of the same age range.

MAIN OUTCOME MEASURES

Weight, height, and waist and hip circumference were measured.

RESULTS

Forty subjects, comprising 91.0% of this cohort, were either overweight (body mass index, 25.0-29.9 kg/m(2)) or obese (body mass index > or = 30 kg/m2). Mean waist circumference was 95.3 cm for IIH, 99.8 cm for the national survey, and 114.5 cm for the obesity clinic cohort (P<0.001), whereas hip circumference was 121 cm for IIH, 118.4 cm for the national survey, and 125.8 cm (P = not significant) for the obesity clinic cohorts. Waist-to-hip ratio, a descriptive measure of body fat distribution approximately reflecting upper to lower body fat ratio, was 0.79 in the patients with IIH, 0.84 in the national survey group, and 0.91 in the obesity clinic cohort (P<0.001; all comparisons were adjusted for age and body mass index).

CONCLUSIONS

In IIH, fat tends to preferentially accumulate in the lower body relative to other obese women of the same range. Whereas most complications of obesity, such as hypertension, diabetes, dyslipidemia, and the metabolic syndrome, are linked to upper body adiposity, IIH may represent a unique condition potentially induced by nonvisceral fat-related mechanisms.

FINANCIAL DISCLOSURE(S)

The authors have no proprietary or commercial interest in any materials discussed in this article.

Comparison of body fatness measurements by near-infrared reactance and dual-energy X-ray absorptiometry in normal-weight and obese black and white women

The aim of the present study was to compare body fat percent (BF %) using single-site near-IR reactance (NIR) and dual-energy X-ray absorptiometry (DXA) in a cohort of normal-weight (BMI < 25 kg/m2) black (n 102) and white (n 71); and obese (BMI > or = 30 kg/m2) black (n 117) and white (n 41) South African women (18-45 years). NIR-derived BF % was significantly correlated with DXA-derived BF % in all groups: normal-weight black (r 0.55, 95 % CI: 0.40, 0.67, P < 0.001) and white (r 0.69, 95 % CI: 0.53, 0.79, P < 0.001) women; obese black (r 0.59, 95 % CI: 0.46, 0.70, P < 0.001) and white (r 0.56, 95 % CI: 0.30, 0.74, P < 0.001) women. NIR under-predicted BF% compared to DXA in black women (normal-weight, - 4.36 (sd 4.13) % and obese, - 3.41 (sd 3.72) %), while smaller mean differences were observed in white women (normal-weight, - 0.29 (sd 4.19) % and obese, - 0.81 (sd 3.09) %), irrespective of normal-weight or obese status (P < 0.001). In obese subjects, NIR-derived BF % did not measure values greater than approximately 45 %, while the maximum DXA-derived measure was 58 %. In conclusion, although there was a significant relationship between NIR- and DXA-derived BF %, NIR under-predicted BF % in normal-weight and obese black South African women compared to DXA, but to a greater extent in subjects with very high levels of adiposity (>45 %). The results of single-site NIR as a measure of BF % should therefore be interpreted with caution, particularly in women of African descent and in those with very high levels of adiposity.

Left ventricular mass, abdominal circumference and age: the Fels longitudinal study

PURPOSE

To determine the relationship of abdominal circumference with increased left ventricular mass (LVM) from young adulthood into old age.

METHODS

Cross-sectional echocardiographic images were taken from 182 men and 220 women in the Fels Longitudinal Study 20 to 75 years of age to determine left ventricular mass. Left ventricular mass was divided by stature raised to the power of 2.7 (LVM/ht2.7) in order to minimize the impact of heart size variation from body size without overcompensating for the adverse effect of obesity. Abdominal circumference was measured and BMI calculated from stature and weight and categories of overweight, obesity and abdominal obesity were determined using published cut points. Regression models were used to describe the relationships of age, abdominal circumference, BMI and self-reported physical activity to LVM/ht2.7.

RESULTS

Age, abdominal circumference and BMI were each positively and significantly related to an increased LVM/ht2.7 in men and women (p < 0.05). In the men, multivariate models indicated that abdominal circumference and BMI were both significantly related to an increased LVM/ht2.7, but the inclusion of BMI in these models for the women reduced the association of abdominal circumference and physical activity below significant levels. In the men, there was also a quadratic association of abdominal circumference with LVM/ht2.7 that was significant along with BMI and physical activity. Sex-specific logistic regressions with BMI and abdominal circumference obesity categories did not change or improve the initial findings in men or women.

CONCLUSIONS

In women, increases in abdominal fatness as reflected in abdominal circumference at any age are linearly related to an increase in LVM/ht2.7, but the relationship of overall fatness as reflected in BMI with LVM/ht2.7 is stronger. In men, both abdominal fatness and overall fatness at any age are linearly related to an increase LVM/ht2.7. However, the significant curvilinear association of abdominal circumference and a linear association of BMI and physical activity with LVM/ht2.7 indicate the possible positive covariate relationship of overall muscle mass with LVM/ht2.7. This reflects the physiological changes with age and demonstrate, in part, the complexity of the interpretations of the inter associations of body composition, the cardiovascular system and the aging process, but the impact among the elderly and the known inadequacy of BMI at these ages remains an area for continued clinical study.

Racial differences in body fat distribution among reproductive-aged women

We examined the influence of race/ethnicity on body fat distribution for a given body mass index (BMI) among reproductive-aged women. Body weight, height, and body fat distribution were measured with a digital scale, wall-mounted stadiometer, and dual-energy x-ray absorptiometry, respectively, on 708 healthy black, white, and Hispanic women 16 to 33 years of age. Multiple linear regression was used to model the relationship between race/ethnicity and different body fat distribution variables after adjusting for BMI, age at menarche, and demographic and lifestyle variables. For a given BMI, white women had the highest total fat mass (FM(total)), trunk fat mass (FM(trunk)), and leg fat mass (FM(leg)), whereas Hispanic women had the highest percentage of FM(trunk) (%FM(trunk)) and trunk-to-limb fat mass ratio (FMR(trunk-to-limb)). Conversely, black women had the lowest FM(total), FM(trunk), percentage body fat mass (%FM), %FM(trunk), and FMR(trunk-to-limb), and the highest percentage of FM(leg). The %FM was similar in whites and Hispanics and lower in blacks. The race x BMI interactions were significant for almost all of the body fat distribution variables. Increasing in differences with increasing BMI were apparent between blacks and whites in FM(trunk), %FM(trunk), FMR(trunk-to-limb), %FM(leg), and %FM, and between blacks and Hispanics in FM(trunk), %FM(trunk), FMR(trunk-to-limb), and FM(leg). In summary, the distribution of body fat for a given BMI differs by race among reproductive-aged women. These findings raise questions regarding universally applied BMI-based guidelines for obesity and have implications for patient education regarding individual risk factors for cardiovascular disease and metabolic complications.

Body weight, lifestyle, dietary habits and gastroesophageal reflux disease

While lifestyle modifications are currently used as first-line treatment for subjects with gastroesophageal reflux disease (GERD), the pathogenetic role of lifestyle factors and consequently, the efficacy of lifestyle measures is controversial. Our aim was to systematically review the pathogenetic link between overweight/obesity, dietary habits, physical activity and GERD, and the beneficial effect of specific recommended changes, by means of the available literature from the 1999 to the present. Obesity, in particular, abdominal obesity, plays a key role in determining GERD symptoms and complications through mechanical and metabolic effects. Controlled weight loss (by diet or surgery) is effective in improving GERD symptoms. No definitive data exist regarding the role of diet and, in particular, of specific foods or drinks, in influencing GERD clinical manifestations. Moderate physical activity seems to be beneficial for GERD, while vigorous activity may be dangerous in predisposed individuals. In conclusion, being obese/overweight and GERD-specific symptoms and endoscopic features are related, and weight loss significantly improves GERD clinical-endoscopic manifestations. The role of dietary behavior, mainly in terms of specific dietary components, remains controversial. Mild routine physical activity in association with diet modifications, i.e. a diet rich in fiber and low in fat, is advisable in preventing reflux symptoms.

Body mass index bias in defining obesity of diverse young adults: the Training Intervention and Genetics of Exercise Response (TIGER) study

The BMI cut-score used to define overweight and obesity was derived primarily using data from Caucasian men and women. The present study evaluated the racial/ethnic bias of BMI to estimate the adiposity of young men and women (aged 17-35 years) using dual-energy X-ray absorptiometry (DXA) determination of percentage body fat (DXA-BF%) as the referent standard. The samples were 806 women and 509 men who were tested from one to three times over 9 months providing 1300 observations for women and 820 observations for men. Linear mixed models (LMM) regression showed that with age and BMI controlled, DXA-BF% of African-American (AA) men and women, Asian-Indian men and women, Hispanic women and Asian women significantly differed from non-Hispanic white (NHW) men and women. For the same BMI of NHW women, the DXA-BF% of AA women was 1.76 % lower, but higher for Hispanic (1.65 %), Asian (2.65 %) and Asian-Indian (5.98 %) women. For the same BMI of NHW men, DXA-BF% of AA men was 4.59 % lower and 4.29 % higher for Asian-Indian men. Using the recommended BMI cut-scores to define overweight and obesity systematically overestimated overweight and obesity prevalence for AA men and women, and underestimated prevalence for Asian-Indian men and women, Asian women and Hispanic women. The present study extends the generalisability of research documenting the racial/ethnic bias of the universal overweight and obesity BMI cut-scores.

Cross-validation of generalised body composition equations with diverse young men and women: the Training Intervention and Genetics of Exercise Response (TIGER) Study

Generalised skinfold equations developed in the 1970s are commonly used to estimate laboratory-measured percentage fat (BF%). The equations were developed on predominately white individuals using Siri's two-component percentage fat equation (BF%-GEN). We cross-validated the Jackson-Pollock (JP) generalised equations with samples of young white, Hispanic and African-American men and women using dual-energy X-ray absorptiometry (DXA) as the BF% referent criterion (BF%-DXA). The cross-sectional sample included 1129 women and men (aged 17-35 years). The correlations between BF%-GEN and BF%-DXA were 0.85 for women and 0.93 for men. Analysis of measurement error showed that BF%-GEN underestimated BF%-DXA of men and women by 1.3 and 3.0 %. General linear models (GLM) confirmed that BF%-GEN systematically underestimated BF%-DXA of Hispanic men and women, and overestimated BF%-DXA of African-American men. GLM were used to estimate BF%-DXA from the JP sum of skinfolds and to account for race/ethnic group bias. The fit statistics (R and standard error of the estimate; see) of the men's calibration model were: white, R 0.92, see 3.0 %; Hispanic, R 0.91, see 3.0 %; African-American, R 0.95, see 2.6 %. The women's statistics were: white and African-American, R 0.86, see 3.8 %; Hispanic, R 0.83, see 3.4 %. These results showed that BF%-GEN and BF%-DXA were highly correlated, but the error analyses documented that the generalised equations lacked accuracy when applied to these racially and ethnically diverse men and women. The inaccuracy was linked to the body composition and race/ethnic differences between these Training Intervention and Genetics of Exercise Response (TIGER) study subjects and the men and women used to develop the generalised equations in the 1970s and using BF%-DXA as the referent criterion.

Comparisons of percentage body fat, body mass index, waist circumference, and waist-stature ratio in adults

BACKGROUND

Body mass index (BMI), waist circumference (WC), and the waist-stature ratio (WSR) are considered to be possible proxies for adiposity.

OBJECTIVE

The objective was to investigate the relations between BMI, WC, WSR, and percentage body fat (measured by dual-energy X-ray absorptiometry) in adults in a large nationally representative US population sample from the National Health and Nutrition Examination Survey (NHANES).

DESIGN

BMI, WC, and WSR were compared with percentage body fat in a sample of 12,901 adults.

RESULTS

WC, WSR, and BMI were significantly more correlated with each other than with percentage body fat (P < 0.0001 for all sex-age groups). Percentage body fat tended to be significantly more correlated with WC than with BMI in men but significantly more correlated with BMI than with WC in women (P < 0.0001 except in the oldest age group). WSR tended to be slightly more correlated with percentage body fat than was WC. Percentile values of BMI, WC, and WSR are shown that correspond to percentiles of percentage body fat increments of 5 percentage points. More than 90% of the sample could be categorized to within one category of percentage body fat by each measure.

CONCLUSIONS

BMI, WC, and WSR perform similarly as indicators of body fatness and are more closely related to each other than with percentage body fat. These variables may be an inaccurate measure of percentage body fat for an individual, but they correspond fairly well overall with percentage body fat within sex-age groups and distinguish categories of percentage body fat.

Racial and geographic issues in gastroesophageal reflux disease

Gastroesophageal reflux disease (GERD) is a common chronic disorder that is associated with a huge economic burden in the western countries and significantly decreased quality of life. This review focuses on the various multicultural issues in the epidemiology, pathophysiology, diagnosis, and treatment of GERD. The prevalence of GERD appears to be highest in North America and Europe, whereas epidemiologic data from the Indian subcontinent, Africa, South America, and the Middle East are sparse. A limited number of studies have elucidated ethnic differences in GERD in multiracial populations. African Americans and Asians appear to be at a lower risk for the development of complicated GERD including Barrett's esophagus (BE). Whether the pathophysiology of GERD differs among different populations remains to be answered satisfactorily. It appears that most of the factors involved in the pathogenesis of GERD, as described in western populations, are present in Asians but at a lower scale. The current recommendations for the management of GERD by the American College of Gastroenterology may not meet the need for different ethnic groups or for different geographic regions. Recognition of language barriers in understanding the common terms used to describe reflux symptoms should be borne in mind while treating GERD patients with different ethnic backgrounds. In addition, a universally accepted definition for treatment success in GERD patients is lacking. Given the negative impact on health-related quality of life, significant cost ramifications, and increased risk for BE and esophageal adenocarcinoma, the study of multicultural issues in GERD should be considered.

Sex and genetic effects on upper and lower body fat and associations with diabetes in multigenerational families of African heritage

Very few studies have comprehensively defined the genetic and environmental influences on body fat storage in the arms and legs and their association with diabetes, especially in families of African heritage. We analyzed body fat distribution by dual-energy x-ray absorptiometry (percentage total fat, percentage trunk fat, percentage arm fat, and percentage leg fat) and fasting serum glucose in 471 individuals (mean age, 43 years) from 8 multigenerational Afro-Caribbean families (mean family size = 51; 3535 relative pairs). Diabetes was inversely associated with percentage leg fat (P = .009) and, to some extent, positively associated with percentage arm fat independent of age, sex, and body size (P = .08), but not with anthropometric or dual-energy x-ray absorptiometric measures of total and central adiposity. Furthermore, percentage leg fat was inversely, whereas percentage arm fat was positively, associated with body mass index, waist circumference, and serum glucose (P < .01). Residual heritability (h2r) for arm and leg fat was significant (P < .01) and high: 62% (for percentage arm fat) and 40% (for percentage leg fat). Moreover, sex-specific h2r for leg fat was considerably higher (P = .02) in women than in men (h2r values, 58% vs 17%, respectively). Genetic correlation (rho(G)) between arm and leg fat was -0.61 (P < .01), suggesting that only 37% of the covariation between these 2 adipose tissue depots may be due to shared genetic influences. This study provides new evidence for a strong genetic and sex contribution to upper and lower body fat, with relatively little covariation between these traits due to shared genes. Our findings also suggest that, in this population, leg fat is associated with diabetes independent of overall adiposity.

Comparisons of body volumes and dimensions using three-dimensional photonic scanning in adult Hispanic-Americans and Caucasian-Americans

BACKGROUND

We studied whether significant differences exist between Hispanic-Americans (H-A) and Caucasian-Americans (C-A) in body dimensions using a newly validated three-dimensional photonic scanner (3DPS).

METHODS

We compared two cohorts of 34 adult U.S.-based H-A (19 females) and 40 adult C-A (25 females) of similar age and body mass index (BMI, kg/m(2)). We measured total body volume (TBV), trunk volume (TV), and other body dimensions, including waist and hip circumferences, estimated percentage body fat (%fat), calculated TV/TBV, and waist-to-hip ratio.

RESULTS

For female cohorts, there were no significant differences in age, weight, height, and 3DPS-measured variables between the two ethnic cohorts. For male cohorts, C-A had greater height (p = 0.014), but there were no significant differences in absolute or proportional volumes or dimensions between the two cohorts.

CONCLUSIONS

Results demonstrate that, in these H-A and C-A cohorts of similar age and BMI, total and regional body volumes and dimensions, as well as their proportions, approximate each other very closely in both sexes; these variables also show similar relationships with %fat in each sex. This is in contradistinction to previous study reports using other measurement techniques.

Gender differences in the relationship between percent body fat (%BF) and body mass index (BMI) in Japanese children

The purpose of the present study was to examine whether gender differences exist in the relationship between percent body fat (%BF) and body mass index (BMI) in Japanese children using a population-based cohort. Subjects are comprised of 187 boys and 163 girls aged 9-10, and 137 boys and 155 girls aged 12-13. Percent BF was measured using a bipedal biometrical impedance analysis (BIA) device. The relationship between %BF and BMI was investigated as a function of age and gender with Pearson's correlation coefficient. Strong linear relationships existed between %BF and BMI, especially in girls (9-10-year-old boys: r=0.779, P<0.0001; 9-10-year-old girls: r=0.975, P<0.0001; 12-13-year-old boys: r=0.786, P<0.0001; 12-13-year-old girls: r=0.975, P<0.000l). These results indicate that %BF can be predicted from BMI in Japanese children aged 9-10 and 12-13 years. The correlations in boys were not as strong as those observed in girls, that is, less variability was explained for girls than for boys. Further study will be necessary to ascertain whether the strong correlation seen among girls will be observed in different age or ethnic groups, and to ascertain the mechanism that produces this gender difference.

A comparative study of methods for diagnosis of obesity in an urban mixed-race population in Minas Gerais, Brazil

Background

Obesity is defined as an excess of total body fat and may be assessed by different methods. The objective of the present study was to establish the discriminatory power of anthropometric data in determining obesity.

Methods

The subjects comprised 685 individuals, aged 20–79 years, sampled from a population-based survey. The following indicators were used: body mass index (BMI), waist circumference (WC) and total body fat percentage estimated with both Siri's equation (%BF Siri) and foot-to-foot bioelectrical impedance analysis (%BF BIA). Sensitivity and specificity of different cut-off points for each method were determined using %BF BIA as reference.

Results

Of 685 participants, 57.6% were aged ≥ 40 years, 69.9% were women and 72.6% self-referred themselves as non-white. To classify obesity based on sex and age among women aged < 40 years, the cut-off points were BMI of 26.0 kg m− 2, WC of 84.0 cm and %BF Siri of 34.0%; in those aged ≥ 40 years, the cut-off points were 28.0 kg m− 2, 90.0 cm and 37.4%, respectively. The cut-off points among men aged < 40 years were BMI of 26.3 kg m− 2, WC of 86.0 cm and %BF Siri of 22.5%, and in those aged ≥ 40 years, 26.3 kg m− 2, 89.0 cm and 24.5%, respectively. BMI was the method with the largest area under the curve (AUC) independent of sex and sex/age, yet no differences were observed in AUC between BMI and WC (P>0.05). Classifying according to skin colour did not change cut-off points in any indicator.

Conclusion

BMI and WC better discriminate obesity among women and men aged ≥ 40 years from a mixed-race population.

Body fat measurement by bioelectrical impedance and air displacement plethysmography: a cross-validation study to design bioelectrical impedance equations in Mexican adults

BACKGROUND

The study of body composition in specific populations by techniques such as bio-impedance analysis (BIA) requires validation based on standard reference methods. The aim of this study was to develop and cross-validate a predictive equation for bioelectrical impedance using air displacement plethysmography (ADP) as standard method to measure body composition in Mexican adult men and women.

METHODS

This study included 155 male and female subjects from northern Mexico, 20-50 years of age, from low, middle, and upper income levels. Body composition was measured by ADP. Body weight (BW, kg) and height (Ht, cm) were obtained by standard anthropometric techniques. Resistance, R (ohms) and reactance, Xc (ohms) were also measured. A random-split method was used to obtain two samples: one was used to derive the equation by the "all possible regressions" procedure and was cross-validated in the other sample to test predicted versus measured values of fat-free mass (FFM).

RESULTS AND DISCUSSION

The final model was: FFM (kg) = 0.7374 * (Ht2 /R) + 0.1763 * (BW) - 0.1773 * (Age) + 0.1198 * (Xc) - 2.4658. R2 was 0.97; the square root of the mean square error (SRMSE) was 1.99 kg, and the pure error (PE) was 2.96. There was no difference between FFM predicted by the new equation (48.57 +/- 10.9 kg) and that measured by ADP (48.43 +/- 11.3 kg). The new equation did not differ from the line of identity, had a high R2 and a low SRMSE, and showed no significant bias (0.87 +/- 2.84 kg).

CONCLUSION

The new bioelectrical impedance equation based on the two-compartment model (2C) was accurate, precise, and free of bias. This equation can be used to assess body composition and nutritional status in populations similar in anthropometric and physical characteristics to this sample.

Anthropometric predictors for the risk of chronic disease in non-diabetic, non-hypertensive young Mexican women

OBJECTIVES

To assess the ability of anthropometric measurements to identify young women at risk of developing diabetes, hypertension and heart disease in the future and to compare cut-off points for common anthropometric measures established with receiver-operating characteristic (ROC) curves with those reported in the literature.

DESIGN

Cross-sectional study.

SUBJECTS

Eight hundred and two young Mexican women living in semi-urban poverty. MEASUREMENTS/METHODS: The ability of anthropometric measures of fatness and fat distribution (body mass index (BMI), summed skinfold thickness (SST), waist circumference (WC), waist-to-hip ratio (WHR), conicity index (CI), abdominal volume index (AVI)) to predict risk of future disease (pre-diabetes: fasting blood glucose 100-126 mg dl-1; pre-hypertension: systolic blood pressure 120-139 mmHg and/or diastolic blood pressure 80-89 mmHg; hypertriglyceridaemia: triglycerides > or =150 mg dl-1; or a combination of risk factors) was assessed using ROC curve analysis.

RESULTS

Twenty-three of the 802 women who were interviewed had incomplete data and 50 (6.4%) were eliminated from the analysis due to hypertension and/or diabetes. Mean age of the remaining 729 women was 29.6 +/- 5.4 years and mean BMI was 27.7 +/- 4.5 kg m-2. There were no significant differences in the area under the ROC curve for BMI, WC, AVI or SST for any of the four outcomes. However, these indices performed significantly better than WHR and CI (P < 0.05). The BMI cut-off points that maximised sensitivity and specificity for the four outcomes were in the range of 27.7-28.4 kg m-2, and for WC were 89.3-91.2 cm. To detect 90% of the cases of any metabolic alteration, the necessary BMI cut-off was 26.1 kg m-2. Younger women (<25 years) were at greater risk than older women for a given BMI increment (P < 0.05).

CONCLUSIONS

We found that BMI and WC cut-off points commonly used for the identification of risk of existing disease were also appropriate in this population for the identification of risk in the future among women without diabetes or hypertension. The early identification of at-risk individuals, prior to the onset of disease, is fundamental particularly in the context of a country with scarce resources that is rapidly undergoing nutrition transition.

The association between benzo[a]pyrene-DNA adducts and body mass index, calorie intake and physical activity

Prior work suggests that body size and fat content may influence carcinogen-DNA adduct levels measured in white blood cells. Here we consider energy balance more broadly by assessing the impact of body mass index (BMI), physical activity and calorie intake on the presence of benzo[a]pyrene-DNA (BP-DNA) adducts in white blood cell DNA. Our cross-sectional study employed subjects from a separately conducted intervention trial. Physical activity and food intake data were collected at 12 and 15 months of follow-up, respectively. BP-DNA adducts were measured by high-performance liquid chromatography (HPLC) in white blood cell samples collected at 12 months of follow-up. Complete data on all variables were available from 143 subjects. Logistic regression showed that BMI was inversely associated with the presence of detectable adducts (OR = 0.90, p = 0.02), and that hours of moderate-intensity physical activity were positively associated with the presence of detectable adducts (OR = 1.04, p = 0.04). These results provide further evidence that body fat content influences carcinogen-DNA adduct levels, probably by altering the distribution of the lipophilic parent compound.

Are there differences in performance, metabolism, and quadriceps muscle activity in black African and Caucasian athletes during brief intermittent and intense exercise?

The purpose of the present study was to determine whether there are any differences in power output (PO) and/or quadriceps muscle (Quad) activity between black African and Caucasian football players during a force-velocity (fv) exercise test, which consisted of performing maximal 6-s sprints against an increasing load. Each subject started the test with a load of 2 kg and then recovered for 5 min before repeating the same test with a load increased by 2 kg. When the pedal frequency did not exceed 130 rev x min(-1), the load was increased by only 1 kg. Each subject attained the load corresponding to his maximal power if an additional increase in load (+1 kg) induced a power decrease. Nine black Africans (mean age 24.2 +/- 3.3 years) and nine Caucasians (24.7 +/- 4.2 years) (matched for stature and aerobic fitness) participated in the fv exercise test. During the test, PO, blood lactate, and the quadriceps electromyography (EMG) root mean square (Quad RMS) were assessed. Higher blood lactate was observed in Caucasians than in black Africans for POs over the load range from 4 kg up to the maximal power. However, PO and Quad RMS values were similar in Caucasians and black Africans. They also had similar lean leg volume (LLV) and consequently produced similar PO/LLV and Quad RMS/LLV values. Overall, our results suggest that Caucasians and black Africans matched for stature, VO(2max), and training background have similar PO and Quad RMS values, but different blood lactate concentrations during brief, intermittent, intense exercise performed on a cycloergometer.

Truncal fat in relation to total body fat: influences of age, sex, ethnicity and fatness

OBJECTIVE

To investigate the influence of age, sex, ethnicity and total fatness on central obesity in four ethnic populations.

DESIGN

Cross-sectional analysis of study subjects enrolled from 1993 to 2005.

SUBJECTS

A multi-ethnic (Caucasian (CA), African-American (AA), Hispanic-American (HA) and Asian (As)) convenience sample of 604 men and 1192 women (aged 18-96 years, body mass index 15.93-45.80 kg/m(2)).

MEASUREMENTS

Total body fat (TBF) and truncal fat were measured by dual-energy X-ray absorptiometry. General linear regression models were used to test for independent associations with log(10)-transformed truncal fat.

RESULTS

For all ethnicities, men had a lower percent body fat and more truncal fat than women. Log(10-)transformed truncal fat increased with TBF approximately as a square root function. At older ages, there was a greater amount of truncal fat in CA, HA and As men (approximately 0.20-0.25 kg/decade) with the effect more pronounced in AA men ( approximately 0.33 kg/decade). For women, the increment of truncal fat per decade was reduced in CA and AA women (approximately 0.07 kg) compared with As and HA women (approximately 0.33 kg). Adjusted for mean values of covariates in our sample, AA had less truncal fat than As.

CONCLUSION

The accumulation of truncal fat is strongly related to age, ethnicity and total fatness in both men and women.

Body mass index and gastroesophageal reflux disease: a systematic review and meta-analysis

BACKGROUND

Gastroesophageal reflux disease (GERD) is a common cause of morbidity and health-care utilization in many countries. Obesity is a potentially modifiable risk factor, but existing studies have conflicting results, possibly due to differences in study design, definitions, or populations.

METHODS

We performed a systematic review and meta-analysis of studies identified using MEDLINE, the Web of Science electronic database, manual literature review, and a review of expert bibliographies. Studies were included if they: (1) evaluated obesity, body mass index (BMI), or another measure of body size; (2) included data on reflux symptoms, esophagitis, or a GERD-related hospitalization; and (3) reported a relative risk or odds ratio (OR) with confidence intervals or provided sufficient data to permit their calculation.

RESULTS

We identified 20 studies that included 18,346 patients with GERD. Studies from the United States demonstrated an association between increasing BMI and the presence of GERD (95% confidence interval [CI]= 1.36-1.80, overweight, OR = 1.57, P value homogeneity = 0.51, 95% CI = 1.89-2.45, obese, OR = 2.15, P= 0.10). Studies from Europe provided heterogeneous results despite stratification for several factors; individual studies demonstrated both positive associations and no association.

CONCLUSIONS

This analysis demonstrates a positive association between increasing BMI and the presence of GERD within the United States; this relationship became apparent only after stratification by country and level of BMI. These results support the evaluation of weight reduction as a potential therapy for GERD. Further studies are needed to evaluate potential mechanisms and any differences in this relationship among different study populations.

Changes in fat-free mass during significant weight loss: a systematic review

OBJECTIVE

To identify the proportion of weight lost as fat-free mass (FFM) by various weight loss interventions.

METHODS

Medline and Embase were systematically searched for reliable measurements of FFM before and after weight loss of >10 kg and eligible data were pooled. In a fixed effect model of % FFM loss/weight loss (%FFML), linear regression analysis was used to determine the influence of degree of caloric restriction, exercise, magnitude of weight loss, initial body mass index (BMI) and type of surgery.

RESULTS

Data were included from 26 cohorts treated with dietary and behavioral interventions and 29 cohorts of bariatric surgery patients. The degree of caloric restriction was positively associated with %FFML (r (2)=0.31, P=0.006) and in three randomized controlled trials exercise was shown to decrease %FFML. Compared with laparoscopic adjustable gastric banding (LAGB), biliopancreatic diversion (BPD) and roux en Y gastric bypass (RYGB) caused greater log(e) (natural log) %FFML (r (2)=0.453, P<0.001). Differences in log(e) %FFML between surgical procedures were independent of initial BMI and magnitude of weight loss.

CONCLUSIONS

The degree of caloric restriction, exercise and rate of weight loss influence the proportion of weight lost as FFM after non-surgical interventions. For surgical interventions, BPD and RYGB result in greater %FFML than LAGB.

Associations of size at birth and dual-energy X-ray absorptiometry measures of lean and fat mass at 9 to 10 y of age

BACKGROUND

Birth weight has been positively associated with risk of overweight in later life. However, little information exists on how weight and length at birth are associated with subsequent lean and total body fat.

OBJECTIVE

We investigated the association between weight and length at birth and body composition and fat distribution in childhood.

DESIGN

Body composition was measured by using dual-energy X-ray absorptiometry in 9-10-y-old subjects (n = 3006 boys and 3080 girls). Weight and length at birth were measured or taken from hospital records.

RESULTS

Birth weight was positively associated with both lean body mass (LBM) and total body fat at 9-10 y of age in both sexes. LBM rose by 320 g per 1-SD increase in birth weight (P < 0.001), and total body fat rose by 2.5% (P = 0.001), but birth weight was unassociated with the fat-to-lean mass ratio (FLR). Ponderal index (PI) at birth (ie, weight/length3) was positively associated with LBM, total body fat, and the FLR in both sexes; the FLR increased by 2.7% in boys (P = 0.021) and by 5.0% in girls per 1-SD increase in PI (P < 0.001). Weight and length at birth did not predict central adiposity; although trunk fat had a strong positive association with PI at birth, this association disappeared after adjustment for total body fat.

CONCLUSIONS

Higher PI at birth is associated with both higher fat and lean mass in childhood but also with an increase in the FLR. PI at birth is a better predictor of subsequent adiposity than is birth weight.

Receiver-operating characteristic analyses of body mass index, waist circumference and waist-to-hip ratio for obesity: Screening in young adults in central south of China

BACKGROUND & AIMS

Recent data suggest that current obesity diagnostic criterion based on body mass index (BMI) above 30 in Caucasians may not be appropriate for Asian populations. Our aim was to identify the usefulness of BMI, waist circumference (WC) and waist-to-hip ratio (WHR) in screening for obesity in an Asian population.

METHODS

A cross-sectional sample of 1109 males and 879 females aged 20-45-yr were recruited. Height, weight, WC, hip circumference and percentage body fat (PBF) were measured in all subjects. Then receiver-operating characteristic analyses were used to evaluate the performances of the three anthropometric indices.

RESULTS

BMI, WC and WHR showed strong positive correlation with PBF (r=0.47-0.75) in both males and females within both age groups. True-positive rates ranged from 82.4% to 94.1% and 68.8% to 86.3% in males and females, respectively. True-negative rates ranged from 64.1% to 84.7% and from 56.9% to 79.0%, respectively. The areas under the curves (AUCs) for WC and BMI were high (0.76-0.92) in both sexes and divided age groups (20-30-yr and 31-45-yr), and those for WHR were a little lower (0.74-0.88).

CONCLUSIONS

BMI and WC are two important predictors for obesity in Chinese, and WHR is an alternative.

Anthropometric predictors of body fat as measured by hydrostatic weighing in Guatemalan adults

BACKGROUND

Most predictive equations currently used to assess percentage body fat (%BF) were derived from persons in industrialized Western societies.

OBJECTIVE

We developed equations to predict %BF from anthropometric measurements in rural and urban Guatemalan adults.

DESIGN

Body density was measured in 123 women and 114 men by using hydrostatic weighing and simultaneous measurement of residual lung volume. Anthropometric measures included weight (in kg), height (in cm), 4 skinfold thicknesses [(STs) in mm], and 6 circumferences (in cm). Sex-specific multiple linear regression models were developed with %BF as the dependent variable and age, residence (rural or urban), and all anthropometric measures as independent variables (the "full" model). A "simplified" model was developed by using age, residence, weight, height, and arm, abdominal, and calf circumferences as independent variables.

RESULTS

The preferred full models were %BF = -80.261 - (weight x 0.623) + (height x 0.214) + (tricipital ST x 0.379) + (abdominal ST x 0.202) + (abdominal circumference x 0.940) + (thigh circumference x 0.316); root mean square error (RMSE) = 3.0; and pure error (PE) = 3.4 for men and %BF = -15.471 + (tricipital ST x 0.332) + (subscapular ST x 0.154) + (abdominal ST x 0.119) + (hip circumference x 0.356); RMSE = 2.4; and PE = 2.9 for women. The preferred simplified models were %BF = -48.472 - (weight x 0.257) + (abdominal circumference x 0.989); RMSE = 3.8; and PE = 3.7 for men and %BF = 19.420 + (weight x 0.385) - (height x 0.215) + (abdominal circumference x 0.265); RMSE = 3.5; and PE = 3.5 for women.

CONCLUSION

These equations performed better in this developing-country population than did previously published equations.

Effects of obesity and sex on the energetic cost and preferred speed of walking

The metabolic energy cost of walking is determined, to a large degree, by body mass, but it is not clear how body composition and mass distribution influence this cost. We tested the hypothesis that walking would be most expensive for obese women compared with obese men and normal-weight women and men. Furthermore, we hypothesized that for all groups, preferred walking speed would correspond to the speed that minimized the gross energy cost per distance. We measured body composition, maximal oxygen consumption, and preferred walking speed of 39 (19 class II obese, 20 normal weight) women and men. We also measured oxygen consumption and carbon dioxide production while the subjects walked on a level treadmill at six speeds (0.50–1.75 m/s). Both obesity and sex affected the net metabolic rate (W/kg) of walking. Net metabolic rates of obese subjects were only ∼10% greater (per kg) than for normal-weight subjects, and net metabolic rates for women were ∼10% greater than for men. The increase in net metabolic rate at faster walking speeds was greatest in obese women compared with the other groups. Preferred walking speed was not different across groups (1.42 m/s) and was near the speed that minimized gross energy cost per distance. Surprisingly, mass distribution (thigh mass/body mass) was not related to net metabolic rate, but body composition (% fat) was ( r2= 0.43). Detailed biomechanical studies of walking are needed to investigate whether obese individuals adopt novel energy saving mechanisms during walking.

Validity of body mass index and waist circumference in the classification of obesity as compared to percent body fat in Chinese middle-aged women

OBJECTIVE

To evaluate the validity of currently recommended obesity cutoffs of body mass index (BMI, in kg/m(2)) and waist circumference (WC, in cm) for Asians by the WHO/IASO/IOTF and for Chinese by the Working Group on Obesity in China (WGOC) using the percentage body fat (%BF)-obesity criteria.

DESIGN

A cross-sectional study.

SUBJECTS

A total of 1122 community-based Hong Kong Chinese women aged between 41 and 63 years.

MEASUREMENTS

Total %BF and percent truncal fat (%TF) were measured using dual-energy X-ray absorptiometry. Anthropometric indices were measured using standard methods.

RESULTS

Regression analyses showed that the BMI cutoffs of 23, 24, 25, and 28 kg/m(2) corresponded to the %BF of 34.8, 35.9, 36.9 and 39.5%, and the 80 cm WC corresponded to 34% TF, respectively. Compared with the %BF obesity cutoff (>/=40%), the WHO/IASO/IOTF BMI-obesity criterion (>/=25) shows a good sensitivity (75%) and specificity (71%); and the WGOC criterion (BMI>/=28) had a low sensitivity (41%) but an excellent specificity (93%), respectively. Corresponding to the BMI cutoffs of 23, 24, 25 and 28 kg/m(2), the %BF cutoffs associated with peak kappa statistic were 33, 34, 35 and 40%, and the relevant %TF linked with 80 cm WC was 33%, respectively.

CONCLUSION

BMI and WC have a good accuracy in the prediction of obesity. Our findings suggest that the WGOC BMI cutoffs are appropriate, but 80 cm of WC is a very rigorous cutoff for this population when using the criteria of 34 and 40% of body fat or truncal fat for overweight and obesity.

Is the current BMI obesity classification appropriate for black and white postmenopausal women?

OBJECTIVE

To evaluate the relation between body fatness (%Fat) and body mass index (BMI) and to evaluate the validity of the BMI standards for obesity established by the NIH in older black and white postmenopausal women.

RESEARCH METHODS

Height, weight, BMI, and %Fat, assessed by DXA, were determined for 296 healthy, independently living women ranging in age from 50 to 80 years (M+/-s.d.; 64.4+/-7.8 years).

RESULTS

Per NIH guidelines, 32% were classified as obese (> or = 30 kg/m2, mean BMI = 28.1+/-5.5 kg/m2). In contrast, using the %Fat criterion of 38% advocated by Lohman to define obesity, 47% of our sample was obese (mean %Fat=37.3+/-6.2%). A moderately high curvilinear relation existed between BMI and %Fat (R = 0.82, SEE = 3.57 %Fat, P<0.05). Race added meaningfully to the prediction of %Fat (P<0.05) such that for the same BMI, black women will have 1% lower body fatness than white women. Based on a %Fat > or = 38 as the criterion for obesity, receiver operating characteristic (ROC) analysis, performed separately by race, indicated that the currently accepted BMI cutpoint for obesity produced low sensitivity (69% and 61% for black and white women, respectively). Alternatively, BMI values > or = 28.4 kg/m2 for black women and > or = 26.9 kg/m2 for white women to define obesity maximized classification accuracy.

CONCLUSION

We conclude that current BMI categories may not be appropriate for identifying obesity among postmenopausal women. Furthermore, the relation between BMI and %Fat is different in black compared to white women but remains constant from the sixth through the eighth decade of life.

Ultrasound of the calcaneus and bone mineral density differs in older black and white women but is not impacted by current physical activity

Black women have lower fracture rates, primarily due to bone-dependent factors; however, the racial differences in quantitative ultrasound (QUS) for older black and white women are poorly characterized, especially in regard to the mediating effects of physical activity. The primary aim of this study was to determine if QUS measures differ in age- and body-size-matched older black and white women and to explore if the racial differences were mediated by differences in current habitual physical activity. We performed dual-energy X-ray absorptiometry (DXA) bone mineral density (BMD) measures and QUS measures [broadband ultrasound attenuation (BUA), speed of sound (SOS), quantitative ultrasound index (QUI)] of the calcaneus in 30 black and 30 white women matched in age (68.3 years) and body mass index (30.0 kg/m2). Black women had greater QUS measures of SOS (1,563.6+/-31.7 vs 1,541.2+/-23.4, p=0.003) and QUI (102.6+/-18.5 vs 90.4+/-15.4, p=0.008), with a strong trend for greater BUA (79.2+/-15.1 vs 71.9+/-15.1 m/sec, p=0.066) compared with white women. As expected, black women had greater BMD measures at all sites; whole body (6.8%, p<0.010), lumbar spine (10.4%, p=0.008), proximal femur (14.2%; p<0.001) and femoral neck (20.3%; p<0.001), compared with white women. Although white women reported expending 45% more energy (p=0.03) in moderate intensity physical activity than black women on a weekly basis, current physical activity did not attenuate the difference in QUS measures between the races. The relations between QUS and BMD measures were similar in black compared with white women. After controlling for BMD, the racial differences in QUS measures were not apparent, precluding the conclusion that bone quality independently contributes to the reduction in fracture risk in older black women. The impact of current physical activity on QUS measures in older black and white women is negligible.

Body mass index is weakly associated with, and not a helpful predictor of, disease progression in men with clinically localized prostate carcinoma treated with radical prostatectomy

BACKGROUND

Several studies have recently suggested an association between body mass index (BMI) and disease progression after radical prostatectomy. In the current study, the authors examined this association and that between the reciprocal of BMI (INVBMI, 1/BMI) and progression-free probability in men treated with radical retropubic prostatectomy (RRP) for clinically localized prostate carcinoma.

METHODS

The authors retrospectively studied 2210 patients who underwent RRP at Memorial Sloan-Kettering Cancer Center between September 1986 and May 2003. Clinicopathologic variables analyzed included BMI (kg/m2), preoperative serum prostate-specific antigen level (ng/mL), clinical T classification, year of surgery, race, biopsy-derived primary and secondary Gleason grades, and INVBMI, known to better correlate with percent body fat than BMI. Cox regression analysis was used to examine the possible association between BMI or its reciprocal with disease progression after controlling for the effects of common prognostic factors. The areas under the receiver operating curve (AUC) for models with and without INVBMI were calculated.

RESULTS

Of the 2210 patients analyzed, 251 experienced disease progression in a median follow-up time of 25.9 months (range, 0-143 months). After adjusting for all clinical variables, both BMI (P = 0.071; hazards ratio [HR] = 1.027) and INVBMI (P = 0.041; HR < 0.001) were associated with disease progression. However, the areas under AUC for models with and without INVBMI were similar (range, 0.794-0.798).

CONCLUSIONS

Although conflicting evidence has been reported regarding the link between obesity and an increased risk of developing prostate carcinoma, as well as an increased risk of developing aggressive disease and prostate carcinoma-related mortality, the authors found weak associations with disease progression for both BMI and INVBMI. These variables were of negligible prognostic value in men who received surgery. Studies with longer follow-up, that examine alternative end points, and that follow treatment(s) besides surgery are needed.

Korean and Caucasian overweight premenopausal women have different relationship of body mass index to percent body fat with age

The aim of the study was to investigate in premenopausal women whether the relationship between percentage body fat (PBF) and body mass index (BMI; in kg/m2) differs between Korean Asians (Ko-As) living in Seoul, South Korea, and Caucasians (Ca) living in New York City. Healthy premenopausal women (50 Ko-As; 38 Ca), ages 22–50 yr, were studied. Weight, height, and PBF by dual-energy X-ray absorptiometry were measured. Total body dual-energy X-ray absorptiometry data were collected using GE-Lunar systems (Prodigy-Korea and DPXL-New York), and all scan analyses were performed by one technician in New York. Similar soft tissue phantoms were used for daily instrument calibrations at both sites. The relationship between PBF and BMI was assessed by multiple regression analysis with race, age, reciprocal of BMI (1/BMI), and a race-by-age interaction as the final independent variables. Race ( P = 0.003) and 1/BMI ( P < 0.001) were significantly related to PBF in this model. A significant race-by-age interaction ( P = 0.039) indicated that the slope of the lines for PBF vs. age differed between Ko-As and Ca. This study demonstrates in a Ko-As sample that the BMI-fat relationship differs significantly from that in a comparable group of Caucasian women. Investigators who use BMI as an index of fatness should be aware of the well documented differences in the relationship of BMI and fatness across race/ethnic groups.

Association of African genetic admixture with resting metabolic rate and obesity among women

OBJECTIVE

To investigate the role of genetic admixture in explaining phenotypic variation in obesity-related traits in a sample of African-American women (n = 145) and to determine significant associations between obesity traits and admixture genetic markers.

RESEARCH METHODS AND PROCEDURES

Associations between genetic admixture and BMI, resting metabolic rate, fat mass, fat-free mass, and bone mineral density were tested using linear regression considering the estimation of admixture by 1) a maximum-likelihood approach (MLA) and 2) a Bayesian analysis.

RESULTS

Both the conservative MLA and the Bayesian approach support an association between African genetic admixture and BMI. Evidence for the associations of African genetic admixture with fat mass and fat-free mass was supported by the Bayesian analysis; the MLA supported an association with bone mineral density. When the individual ancestry informative markers that were used to estimate admixture were tested for associations with BMI, significant associations were identified in chromosomes 1, 11, and 12.

DISCUSSION

These results provide evidence supporting the application of admixture mapping methods to the identification of genes that result in higher levels of obesity among African-American women. Further research is needed to replicate and further explore these findings.