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

Eating frequency is associated with energy intake but not obesity in midlife women

Midlife women tend to gain weight with age, thus increasing risk of chronic disease. The purpose of this study was to examine associations between overweight/obesity and behavioral factors, including eating frequency, in a cross-sectional national sample of midlife women (n = 1,099) (mean age = 49.7 years, and BMI = 27.7 kg/m²). Eating behaviors and food and nutrient intakes were based on a mailed 1-day food record. BMI was calculated from self-reported height and weight, and level of physical activity was assessed by self-reported questionnaire. After exclusion of low-energy reporters (32% of sample), eating frequency was not associated with overweight/obesity (P > 0.05) and was not different between BMI groups (normal, 5.21 ± 1.79; overweight, 5.16 ± 1.74; obese, 5.12 ± 1.68, P = 0.769). Adjusted logistic regression showed that eating frequency, snacking frequency, breakfast consumption, eating after 10 PM and consuming meals with children or other adults were not significantly associated with overweight/obesity. Total energy intake increased as eating frequency increased in all BMI groups, however, obese women had greater energy intake compared to normal weight women who consumed the same number of meals and snacks. Intake of fruit and vegetables, whole grains, dietary fiber, dairy, and added sugars also increased as eating frequency increased. While eating frequency was not associated with overweight/obesity, it was associated with energy intake. Thus, addressing total energy intake rather than eating frequency may be more appropriate to prevent weight gain among midlife women.

Low-fat dietary pattern and change in body-composition traits in the Women's Health Initiative Dietary Modification Trial

BACKGROUND

The Women's Health Initiative Dietary Modification (DM) Trial was a randomized controlled trial that compared the effects of a low-fat (≤20% of total energy) or a usual diet in relation to chronic disease risk in postmenopausal women.

OBJECTIVE

We characterized long-term body-composition changes associated with the DM trial and potential modifiers of these associations.

DESIGN

In the DM trial, 48,835 women aged 50-79 y were randomly assigned to intervention (40%) or comparison (60%) groups. We studied a subset with whole-body dual-energy X-ray absorptiometry scans at baseline and during follow-up. Changes in fat mass (FM), lean mass (LM), and percentage body fat between the intervention (n = 1580) and comparison (n = 2731) groups at years 1, 3, and 6 were compared. By using generalized estimating equations, we calculated overall differences between groups and tested for interactions with age, diabetes, race-ethnicity (white, black, and Hispanic), body mass index (BMI), and hormone therapy (HT).

RESULTS

The intervention women experienced significantly greater reductions in percentage body fat, FM, and LM at years 1 and 3 than did women in the comparison group (all P < 0.05). At year 6, only the FM change was significantly different between groups. Overall, the intervention was associated with reductions in percentage body fat (-0.8%; 95% CI: -1.0%, -0.6%), FM (-1.1 kg; 95% CI: -1.3, -0.8 kg), and LM (-0.17 kg; 95% CI: -0.28, -0.06 kg) during follow-up (all P < 0.003). Intervention associations varied by race-ethnicity, BMI, diabetes, and HT and remained significant after adjustment for physical activity.

CONCLUSION

This intervention was associated with modest long-term body-composition changes; the findings were more robust in years 1 and 3. This trial was registered at clinicaltrials.gov as NCT00000611.

Comparison of dual-energy x-ray absorptiometric and anthropometric measures of adiposity in relation to adiposity-related biologic factors

Dual-energy x-ray absorptiometry (DXA) can provide accurate measurements of body composition. Few studies have compared the relative validity of DXA measures with anthropometric measures such as body mass index (BMI) and waist circumference (WC). The authors compared correlations of DXA measurements of total fat mass and fat mass percent in the whole body and trunk, BMI, and WC with obesity-related biologic factors, including blood pressure and levels of plasma lipids, C-reactive protein, and fasting insulin and glucose, among 8,773 adults in the National Health and Nutrition Examination Survey (1999-2004). Overall, the magnitudes of correlations of BMI and WC with the obesity-related biologic factors were similar to those of fat mass or fat mass percent in the whole body and trunk, respectively. These observations were largely consistent across different age, gender, and ethnic groups. In addition, in both men and women, BMI and WC demonstrated similar abilities to distinguish between participants with and without the metabolic syndrome in comparison with corresponding DXA measurements. These data indicate that the validity of simple anthropometric measures such as BMI and WC is comparable to that of DXA measurements of fat mass and fat mass percent, as evaluated by their associations with obesity-related biomarkers and prevalence of metabolic syndrome.

Receiver-operating characteristics of adiposity for metabolic syndrome: the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study

OBJECTIVE

To assess the predictive values of various adiposity indices for metabolic syndrome (MetS) among adults using baseline data from the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) cohort.

DESIGN

In a cross-sectional study, BMI, waist circumference (WC), body composition by dual-energy X-ray absorptiometry (DEXA) and metabolic risk factors such as TAG, HDL cholesterol, blood pressure, fasting glucose and insulin, uric acid and C-reactive protein were measured. Receiver-operating characteristic (ROC) curves and logistic regression analyses were conducted.

SETTING

Baltimore, Maryland.

SUBJECTS

White and African-American US adults (n 1981), aged 30-64 years.

RESULTS

In predicting risk of MetS using obesity-independent National Cholesterol Education Program Adult Treatment Panel III criteria, percentage total body fat mass (TtFM) assessed using DEXA measuring overall adiposity had no added value over WC. This was true among both men (area under the ROC curve (AUC) = 0.680 v. 0.733 for TtFM and WC, respectively; P < 0.05) and women (AUC = 0.581 v. 0.686). Percentage rib fat mass (RbFM) was superior to TtFM only in women for MetS (AUC = 0.701 and 0.581 for RbFM and TtFM, respectively; P < 0.05), particularly among African-American women. Elevated percentage leg fat mass (LgFM) was protective against MetS among African-American men. Among white men, BMI was inferior to WC in predicting MetS. Optimal WC cut-off points varied across ethnic-sex groups and differed from those recommended by the National Institutes of Health/North American Association for the Study of Obesity.

CONCLUSIONS

The study provides evidence that WC is among the most powerful tools to predict MetS, and that optimal cut-off points for various indices including WC may differ by sex and race.

Physical activity and obesity gap between black and white women in the southeastern U.S

BACKGROUND

Differences between black and white women in the associations of sedentary and active behaviors and obesity are mostly unknown.

PURPOSE

To examine associations of sedentary and active behaviors with BMI, a marker of overall obesity, in a large group of black and white women and to determine whether there are differences by race in these associations.

METHODS

Associations between time spent in sedentary and active behaviors and BMI were examined using cross-sectional data collected from 2002 to 2006 at enrollment into the Southern Community Cohort Study (SCCS) from 22,948 black and 7830 white women living in the southeastern U.S. These associations were examined using linear and polytomous logistic regression models controlling for age, race, income, education, occupational status, tobacco use, marital status, and comorbidities.

RESULTS

Time spent in sedentary behaviors was directly related to BMI whereas time spent in active behaviors such as moderate and vigorous physical activity was inversely related to BMI, with stronger associations for whites than blacks. White women in the highest quartile of sedentary behaviors were more likely to be moderately (BMI=30-39) or severely (BMI>40) obese than women in the lowest quartile (OR=2.3, 95% CI=1.8, 2.9 for moderate, and OR=4.0, 95% CI=3.1, 5.3 for severe obesity), whereas the ORs among similarly sedentary black women were modestly elevated (ORs of 1.4, 95% CI=1.2, 1.6; and 1.6, 95% CI=1.4, 1.8).

CONCLUSIONS

There are significant differences in the association of physical activity patterns and obesity between black and white women living in the southeastern U.S. Although most guidelines for prevention of obesity and maintaining weight promote increased time in moderate and vigorous physical activity, these results indicate that a reduction in sedentary behavior time may represent another useful strategy in this population.

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.

Comparison of the classification of obesity by BMI vs. dual-energy X-ray absorptiometry in the Newfoundland population

Although BMI is the most widely used measure of obesity, debate still exists on how accurately BMI defines obesity. In this study, adiposity status defined by BMI and dual-energy X-ray absorptiometry (DXA) was compared in a large population to evaluate the accuracy of BMI. A total of 1,691 adult volunteers from Newfoundland and Labrador participated in the study. BMI and body fat percentage (%BF) were measured for all subjects following a 12-h fasting period. Subjects were categorized as underweight (UW), normal weight (NW), overweight (OW), or obese (OB) based on BMI and %BF criteria. Differences between the two methods were compared within gender and by age-groups. According to BMI criteria, 1.2% of women were classified as UW, 44.2% as NW, 34.2% as OW, and 20.3% as OB. When women were classified according to %BF criteria, 2.2% were UW, 29.6% were NW, 30.9% were OW, and 37.1% were OB. The overall discrepancy between the two methods for women was substantial at 34.7% (14.6% for NW and 16.8% for OB, P < 0.001). In men, the overall discrepancy was 35.2% between BMI and DXA (17.6% for OW and 13.5% for OB, P < 0.001). Misclassification by BMI was dependent on age, gender, and adiposity status. In conclusion, BMI misclassified adiposity status in approximately one-third of women and men compared with DXA. Caution should be taken when BMI is used in clinical and scientific research as well as clinical practice.

Increased fat mass and high incidence of overweight despite low body mass index in patients with spinal muscular atrophy

Body composition is sparsely described in spinal muscular atrophy (SMA). Body (BMI, mass/height in m(2)), fat-free (FFMI, lean mass/height in m(2)) and fat (FMI, fat mass/height in m(2)) mass indexes were estimated in 25 children (aged 5-18) with SMA (2 type I, 13 type II, 10 type III) using dual-energy radiograph absorptiometry and anthropometric data referenced to gender and age-matched healthy children (NHANES III, New York Pediatric Rosetta Body Project). BMI was 50th percentile in 11 (44%) and 85th in 5 (20%). FFMI was reduced (p<0.005) and FMI was increased (p<0.005) in the overall study cohort. FMI was 50th, 85th and 95th percentiles in 19 (76%), 10 (40%) and 5 (20%) subjects, respectively. Using a receiver operator characteristic curve, BMI above 75th, 50th and 3rd percentiles maximized sensitivity and specificity for FMI 95th, 85th and 50th percentiles, respectively. Children with SMA have reduced lean and increased fat mass compared to healthy children. Obesity is a potentially important modifiable source of morbidity in SMA.

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.

Change in body mass index is a stronger predictor of change in fat mass than lean mass in elderly black and white women

The aim of this study was to determine the relation between change in body mass index (BMI) and changes in fat mass (FM), lean soft tissue (LST), and percentage body fat (%Fat) in elderly (67.6 +/- 6.0 years) women varying in race (53 black, 144 white) who underwent measurements of BMI, FM, LST, and %Fat at baseline and after 2 years. The group did not markedly change body composition over 2 years (BMI = -0.1 +/- 1.5 kg/m(2), P = 0.53; FM = 0.0 +/- 2.8 kg, P = 0.95; LST = -0.4 +/- 1.7 kg, P < 0.001; %Fat = 0.3 +/- 2.0%, P = 0.06). Change in BMI predicted change in FM (r = 0.90, SEE = 1.19 kg FM, P < 0.001) but was less predictive of change in %Fat (r = 0.64, SEE = 1.54%Fat, P < 0.001). Change in BMI was curvilinearly related to change in LST adjusted for change in height (R = 0.76, SEE = 1.10 kg LST, P < 0.001). Change in BMI more strongly predicts change in FM than LST and could be used to monitor change in FM in community-dwelling women.

Climate amenity and BMI

OBJECTIVES

Our goal was to examine the relationship between BMI and climate amenable for physical activity at the county level in the U.S.

RESEARCH METHODS AND PROCEDURES

Using Geographic Information Systems tools and 6-year National Oceanic and Atmospheric Administration station hourly weather records, an index of amenable climate was derived for all U.S. counties. This index was linked to individual BMI in a multi-level analysis that accounted for other individual characteristics from the 2002 survey of the Behavioral Risk Factor Surveillance System.

RESULTS

There was an inverse relationship between climate amenable to physical activity and BMI at the county level after controlling for individual risk factors, county road density, and median household income and unemployment rate. Residents in high climate-amenity counties tended to have a lower BMI.

DISCUSSION

The contribution of less amenable climate to overweight and obesity in the U.S. is likely to be substantial because it cuts across wide geographic areas. Health promotion strategies that promote mixed land use or other urban design conducive to walking and other physical activities should consider broader environmental disamenities to mitigate their influence. Strategies for outdoor physical activity should also be tailored for people of different racial groups and educational backgrounds due to observed differences in their response to climate amenity.

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.

Association of eating frequency with body fatness in pre- and postmenopausal women

OBJECTIVE

To examine associations between eating frequency (EF) and body fatness in pre- and postmenopausal women, after excluding potential low-energy reporters.

RESEARCH METHODS AND PROCEDURES

In this cross-sectional study of 220 free-living women, 64 pre- and 50 postmenopausal non-low-energy-reporting women were further analyzed (age, 24 to 74 years; BMI, 18.5 to 38.6 kg/m2). Anthropometric and body composition measurements (DXA) were performed in all study participants. EF, energy, and macronutrient intake were assessed by 3-day food record. Physical activity level and energy expenditure were assessed by self-reported questionnaire.

RESULTS

No association between EF and adiposity indices was detected in premenopausal women. In contrast, EF was positively correlated with percentage body fat in postmenopausal women (r = 0.30, p = 0.03). EF was positively correlated with total energy intake in both groups and with total energy expenditure in premenopausal women only (r = 0.34, p = 0.02). Multivariate analysis revealed that, in postmenopausal women, EF was a significant predictor of body fatness (standardized beta = 0.41, p = 0.01).

DISCUSSION

Frequent eating was not found to be related to adiposity in premenopausal women, but it was associated with increased body fat in postmenopausal women. Possible explanations could be that the frequent eating is not associated with a physically active lifestyle in postmenopausal women or that frequent eating predisposes women after menopause to a higher energy intake by increasing food stimuli and rendering it more difficult for them to control energy balance.

Body mass index and body composition measures by dual x-ray absorptiometry in patients aged 10 to 21 years with spinal cord injury

BACKGROUND/OBJECTIVE

To determine the body composition of adolescents with spinal cord injury (SCI) and to assess whether established cutoff values for obesity determined by body mass index (BMI) are valid for this population.

METHODS

Sixty patients, aged 10-21 years, with traumatic SCI (50 with paraplegia and 10 with tetraplegia) were compared with 60 gender-, age-, and BMI-matched controls (CTRL). Dual-energy x-ray absorptiometry was used to estimate regional and total bone mineral content, lean tissue mass, fat tissue mass, and body fat percentage. BMI was calculated from measured weight and stature (kg/m2).

RESULTS

Total percent body fat was significantly higher in the paraplegia group (31.4% +/- 1.2%; mean +/- SE) than in the tetraplegia and CTRL groups (25.7% +/- 2.7% and 22.9% +/- 1.1%, respectively). This change in percent total body fat was associated with a reduction of lean tissue mass in the paraplegia (37.6 +/- 1.1 kg; mean +/- SE) and tetraplegia (32.8 +/- 2.5 kg) subjects as compared to the CTRL group (46.2 +/- 1.0 kg; P < 0.001). Total fat mass was significantly greater in the paraplegia group (19.3 +/- 1.3 kg) than the CTRL and tetraplegia groups (14.9 +/- 1.2 kg and 11.7 +/- 3.0 kg, respectively). Regional measurements revealed that the greatest reduction of lean tissue mass in the SCI subjects occurred in the lower extremities, followed by the trunk. As a result of these changes in body composition, the optimal BMI for classifying obesity (trunk fat percent >30 in males and >35 in females) in subjects with SCI was 19 kg/m2 as compared to 25 kg/m2 in able-bodied subjects.

CONCLUSIONS

Patients aged 10 to 21 years with SCI have significantly decreased lean tissue mass and bone mineral content, and increased fat mass. As a result, traditional BMI cutoff criteria significantly underestimate obesity in this population. New clinically applicable criteria to define obesity should be established for SCI children and adolescents with SCI.