Comparing Trends in BMI and Waist Circumference

The nature of excess body weight may be changing over time to one of greater central adiposity. The aim of this study is to determine whether BMI and waist circumference (WC) are increasing proportionately among population subgroups and the range of bodyweight, and to examine the public health implications of the findings. Our data are from two cross‐sectional surveys (the US National Health and Nutrition Examination Studies (NHANES) in 1988–1994 (NHANES III) and 2005–2006), from which we have used samples of 15,349 and 4,176 participants aged ≥20 years. Between 1988–1994 and 2005–2006 BMI increased by an average of 1.8 kg/m² and WC by 4.7 cm (adjusted for sex, age, race‐ethnicity, and education). The increase in WC was more than could be attributed simply to increases in BMI. This independent increase in WC (of on average, 0.9 cm) was consistent across the different BMI categories, sexes, education levels, and race‐ethnicity groups. It occurred in younger but not older age groups. Overall in each BMI category, the prevalence of low‐risk WC decreased and the prevalence of increased‐risk or substantially increased‐risk WC increased. These results suggest that the adverse health consequences associated with obesity may be increasingly underestimated by trends in BMI alone. Since WC is closely linked to adverse cardiovascular outcomes, it is important to know the prevailing trends in both of these parameters.     

Development of Health‐Related Waist Circumference Thresholds Within BMI Categories

Objective: To develop and cross‐validate waist circumference (WC) thresholds within BMI categories. The utility of the derived values was compared with the single WC thresholds (women, 88 cm; men, 102 cm) recommended by NIH and Health Canada. Research Methods and Procedures: The sample included adults classified as normal weight (BMI = 18.5 to 24.9), overweight (BMI = 25 to 29.9), obese I (BMI = 30 to 34.9), and obese II+ (BMI ≥ 35) from the Third U.S. National Health and Nutrition Examination Survey (NHANES III; n = 11, 968) and the Canadian Heart Health Surveys (CHHS; n = 6286). Receiver operating characteristic curves were used to determine the optimal WC thresholds that predicted high risk of coronary events (top quintile of Framingham scores) within BMI categories using the NHANES III. The BMI‐specific WC thresholds were cross‐validated using the CHHS. Results: The optimal WC thresholds increased across BMI categories from 87 to 124 cm in men and from 79 to 115 cm in women. The validation study indicated improved sensitivity and specificity with the BMI‐specific WC thresholds compared with the single thresholds. Discussion: Compared with the recommended WC thresholds, the BMI‐specific values improved the identification of health risk. In normal weight, overweight, obese I, and obese II+ patients, WC cut‐offs of 90, 100, 110, and 125 cm in men and 80, 90, 105, and 115 cm in women, respectively, can be used to identify those at increased risk.     

Waist Circumference is an Independent Correlate of Errors in Self‐Reported BMI

Although there are issues of reporting bias surrounding the use of self‐reported BMI, it is frequently the method employed to establish the prevalence of obesity. The goal of this study was to assess whether, independently of measured BMI, waist circumference (WC) was associated with the magnitude of the difference between self‐reported and measured BMI within a large sample of European‐American (EA) and African‐American (AA) adults. Self‐reported height and weight, and measured height, weight, and WC were collected on 12,809 adults (61% women, 66% EA) aged 18–65 years. Mean negative BMI differences (self‐reported minus measured BMI) were identified in all race‐by‐sex groups (AA men: ?0.55; EA men: ?0.63; AA women: ?0.91; EA women: ?0.67). WC was negatively associated with the BMI difference such that a higher WC was associated with greater under‐reporting of BMI. However, after adjusting for age and measured BMI, WC was positively associated with the BMI difference in all race‐by‐sex groups. These results suggest that WC could be useful in gaining an insight into people's awareness of their own body size and fatness.     

BMI and Waist Circumference as Predictors of Well‐being in Older Adults: Findings From the English Longitudinal Study of Ageing

The aim of this study is to examine the association of BMI and waist circumference (WC), with a quality of life (QoL) indicator designed for older ages (CASP19), and with depressive symptoms (Centre for Epidemiologic Studies Depression Scale). We included 8,688 individuals aged ≥52 years who participants of Wave 2 (2004–2005) and Wave 3 (2006–2007) of the English Longitudinal Study of Ageing (ELSA). To explore cross‐sectional relationships (2004–2005), we fitted regression models for BMI and WC (included simultaneously) as our predictors of QoL and depressive symptoms adjusted for covariates. To explore longitudinal relationships, BMI and waist at baseline (2004–2005) were related to the each outcome variable measured at follow‐up (2006–2007), and adjusted for baseline characteristics (2004–2005). For a given BMI, larger WC was associated with lower QoL and higher risk of depressive symptoms for women in cross‐sectional and longitudinal analyses. By contrast for a given WC increased BMI for women was positively associated with QoL and lower odds of depressive symptoms. In men, for a given BMI, increased WC was related to QoL only cross‐sectionally; neither WC nor BMI at baseline were associated with depressive symptoms (cross‐sectionally or longitudinally). In conclusion among older people, for a given BMI, increased WC was related with higher risk of poor QoL and, for women, of depressive symptoms; whereas for a given WC, increased BMI had a protective effect on QoL for women.     

Waist Circumference,BMI, Smoking,and Mortality in Middle‐Aged Men and Women

Objective: Measurement of waist circumference alone as a proxy of abdominal fat mass has been suggested as a simple clinical alternative to BMI for detecting adults with possible health risks due to obesity. Research Methods and Procedures: From 1993 to 1997, 27, 178 men and 29, 875 women, born in Denmark, 50 to 64 years of age, were recruited in the Danish prospective study Diet, Cancer and Health. By the end of the year 2000, 1465 deaths had occurred. We evaluated the relationship between waist circumference and BMI (simultaneously included in the model) and all‐cause mortality. We used Cox regression models to estimate the mortality‐rate ratios and to consider possible confounding from smoking. Results: Waist circumference among both men and women showed a strong dose‐response type of relationship with mortality when adjusted for BMI, whereas the low range of BMI was inversely associated with mortality when adjusted for waist circumference. A 10% larger waist circumference corresponded to a 1.48 (95% confidence interval: 1.36 to 1.61) times higher mortality over the whole range of waist circumference. The associations were independent of age and time since baseline examination. Restriction to never smokers showed a similar pattern, but a weakening of the associations. Discussion: Despite the high correlation between waist circumference and BMI, the combination may be very relevant in clinical practice because waist circumference for given BMI was a strong predictor of all‐cause mortality. The inverse association between BMI and mortality for given waist circumference was diminished in never smokers, particularly for high values of BMI.     

Relationship of BMI,Waist Circumference,and Weight Change with Use of Health Services by Older Adults

Objective: To examine the relationship of BMI, waist circumference (WC), and weight change with use of health care services by older adults. Research Methods and Procedures: This was a prospective cohort study conducted from 2001 to 2003 among 2919 persons representative of the non‐institutionalized Spanish population ≥60 years of age. Analyses were performed using logistic regression, with adjustment for age, educational level, size of place of residence, tobacco use, alcohol consumption, and presence of chronic disease. Results: Obesity (BMI ≥ 30 kg/m²) and abdominal obesity (WC >102 cm in men and >88 cm in women) in 2001 were associated with greater use of certain health care services among men and women in the period 2001–2003. Compared with women with WC ≤ 88 cm, women with abdominal obesity were more likely to visit primary care physicians [odds ratio (OR): 1.36; 95% confidence limit (CL): 1.06–1.73] and receive influenza vaccination (OR: 1.30; 95% CL: 1.03–1.63). Weight gain was not associated with greater health service use by either sex, regardless of baseline BMI. Weight loss was associated with greater health service use by obese and non‐obese subjects of both sexes. In comparison with those who reported no important weight change, non‐obese women who lost weight were more likely to visit hospital specialists (OR: 1.45; 95% CL: 1.02–2.06), receive home medical visits (OR: 1.61; 95% CL: 1.06–2.45), be hospitalized (OR: 1.88; 95% CL: 1.29–2.74), and have more than one hospital admission (OR: 2.31; 95% CL: 1.19–4.47). Discussion: Obesity and weight loss are associated with greater health service use among the elderly.     

Trends in Waist Circumference among U.S. Adults

Objective: Waist circumference has been proposed as a measure of obesity or as an adjunct to other anthropometric measures to determine obesity. Our objective was to examine temporal trends in waist circumference among adults in the U.S. Research Methods and Procedures: We used data from 15, 454 participants ≥20 years old in National Health and Nutrition Examination Survey (NHANES) III (1988 to 1994) and 4024 participants ≥20 years old from National Health and Nutrition Examination Survey 1999 to 2000. Results: The unadjusted waist circumference increased from 95.3 (age‐adjusted, 96.0 cm) to 98.6 (age‐adjusted, 98.9 cm) cm among men and from 88.7 (age‐adjusted 88.9 cm) to 92.2 (age‐adjusted 92.1 cm) cm among women. The percentiles from the two surveys suggest that much of the waist circumference distribution has shifted. Statistically significant increases occurred among all age groups and racial or ethnic groups except men 30 to 59 years old, women 40 to 59 and ≥70 years old, and women who were Mexican American or of “other” race or ethnicity. Discussion: These results demonstrate the rapid increase in obesity, especially abdominal obesity, among U.S. adults. Unless measures are taken to slow the increase in or reverse the course of the obesity epidemic, the burden of obesity‐associated morbidity and mortality in the U.S. can be expected to increase substantially in future years.     

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

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

BMI and Waist Circumference; Cross-Sectional and Prospective Associations with Blood Pressure and Cholesterol in 12-Year-Olds

Objective

Childhood and adolescent overweight, defined by body mass index (BMI) are associated with an increased risk of cardiovascular disease in later life. Abdominal adiposity may be more important in associations with cardiovascular diseases but waist circumference (WC) has been rarely studied in children. We studied associations between BMI and WC and blood pressure (BP) and cholesterol in 12-year-old children and prospectively changes in BMI or WC status between age 8 and 12 years and BP and cholesterol at age 12.

Study Design

Weight, height, WC, BP and cholesterol concentrations were measured in 1432 children at age 12 years. Linear regression was used to study the associations between high BMI and large WC (>90^th percentile) and BP and cholesterol.

Results

Systolic BP was 4.9 mmHg higher (95% (CI 2.5, 7.2) in girls and 4.2 mmHg (95%CI 1.9, 6.5) in boys with a high BMI. Large WC was also associated with higher systolic BP in girls (3.7 mmHg (95%CI 1.3, 6.1)) and boys (3.5 mmHg (95%CI 1.2, 5.8)). Diastolic BP and cholesterol concentrations were significantly positively (HDL cholesterol negatively) associated with high BMI and large WC, too. Normal weight children with a history of overweight did not have higher blood pressure levels or adverse cholesterol concentrations than children that were normal weight at both ages.

Conclusion

A high BMI and large WC were associated with higher BP levels and adverse cholesterol concentrations. WC should be taken into account when examining cardiovascular risk factors in children.     

Cut‐points for Waist Circumference in Europids and South Asians

There is little strong evidence that currently recommended higher waist circumference cut‐points for Europids compared with South Asians are associated with similar risk for type 2 diabetes. This study was designed to provide such evidence. Longitudinal studies over 5 years were conducted among 5,515 Europid and 2,214 ethnically South Asian participants. Age‐standardized diabetes incidence at different levels of waist circumference and incidence difference relative to a reference value were calculated. The Youden Index was used to determine waist circumference cut‐points. At currently recommended cut‐points, estimated annual diabetes incidence for a 50‐year‐old Europid was <0.6% for both sexes, and for a 50‐year‐old South Asian, 5.8% for men and 2.1% for women. Annual diabetes incidence of 1% was observed for a 50 year old at a waist circumference 35–40 cm greater in Europid compared to South Asian men and women. Incidence difference between recommended cut‐points and a reference value (80 cm in men, 70 cm in women) was 0.3 and 4.4% per year for Europid and South Asian men, and 0.2 and 0.8% per year for Europid and South Asian women, respectively. Waist circumference cut‐points chosen using the Youden Index were shown to be dependent on obesity levels in the population. The much higher observed risk of diabetes in South Asians compared to Europids at the respective recommended waist circumference cut‐points suggests that differences between them should be greater. Approaches that use the Youden Index to select waist circumference cut‐points are inappropriate and should not be used for this purpose.     

Fitness Alters the Associations of BMI and Waist Circumference with Total and Abdominal Fat

Objective: We tested the following hypotheses in black and white men and women: 1) for a given BMI or waist circumference (WC), individuals with moderate cardiorespiratory fitness (CRF) have lower amounts of total fat mass and abdominal subcutaneous and visceral fat compared with individuals with low CRF; and 2) exercise training is associated with significant reductions in total adiposity and abdominal fat independent of changes in BMI or WC. Research Methods and Procedures: The sample included 366 sedentary male (111 blacks and 255 whites) and 462 sedentary female (203 blacks and 259 whites) participants in the HERITAGE Family Study. The relationships between BMI and WC with total fat mass (determined by underwater weighing) and abdominal subcutaneous and visceral fat (determined by computed tomography) were compared in subjects with low (lower 50%) and moderate (upper 50%) CRF. The effects of a 20‐week aerobic exercise training program on changes in these adiposity variables were examined in 86% of the subjects. Results: Individuals with moderate CRF had lower levels of total fat mass and abdominal subcutaneous and visceral fat than individuals with low CRF for a given BMI or WC value. The 20‐week aerobic exercise program was associated with significant reductions in total adiposity and abdominal fat, even after controlling for reductions in BMI and WC. With few exceptions, these observations were true for both men and women and blacks and whites. Discussion: These findings suggest that a reduction in total adiposity and abdominal fat may be a means by which CRF attenuates the health risk attributable to obesity as determined by BMI and WC.     

Association of Long‐term Change in Waist Circumference With Insulin Resistance

Recent studies have shown that fat accumulation is associated with insulin resistance; however, the risks associated with long‐term changes and fluctuations in central fatness are less clear. This study examined the longitudinal relationship between waist circumference (WC) and insulin resistance using three dimensions of WC: baseline WC, slope of linear changes in WC, and fluctuation of WC around the slope during 20 years of follow‐up. Anthropometry, insulin resistance (homeostasis model assessment (HOMA_IR)), and lifestyle factors were obtained in a population‐based, prospective observational study (Coronary Artery Risk Development in Young Adults (CARDIA)) during 1985–2006, excluding participants who had been diagnosed with diabetes at any examination. After adjusting for socio‐demographic and lifestyle factors, the evolution of HOMA_IR from CARDIA year 15 to 20 was 6.9% higher per standard deviation of year 0 WC (P trend <0.0001) and 6.3% higher per standard deviation increase in the change in WC over the long term (P trend <0.0001). However, WC fluctuations around the linear change were not associated with insulin resistance or its evolution. The level of HOMA_IR increased substantially with steeper linear WC slope among initially thinner participants at baseline, whereas this association tended to be weaker in those with higher initial WC (P interaction <0.0001). We conclude that year 0 WC and long‐term increment in WC are associated with worsening insulin resistance. However, the association of HOMA_IR with slope of WC change may vary across the range of initial WC.     

Waist Circumference and Abdominal Obesity among Older Adults: Patterns,Prevalence and Trends

Objectives

To describe the patterns and trends in waist circumference and abdominal obesity for those aged 70–89 contrasting the standard and new age-related cut-points, and to investigate how they vary with time, age and educational level.

Methods

The subjects were 7129 men and 9244 women aged 70–89 years who participated in the Health Survey for England during 1993–2010. The outcome measures were the percentiles of waist circumference and standard and new indicators of abdominal obesity based on waist circumference. Binomial and quantile regression were used to investigate the relationship with key explanatory variables.

Results

The distribution of waist circumference among community-dwelling older adults in England has shifted upwards since 1993 (an increase in median of 4.5 cm in men and 5.1 cm in women). The prevalence of abdominal obesity has increased, while those in the low-risk group have decreased. Abdominal obesity was higher in those aged 70–79 compared to 80–89, and in those who left education earlier. The prevalence of abdominal obesity varies considerably with new and standard cut-points, which makes it impractical to use the new ones on a population that includes subjects across the adult age range.

Conclusions

Obesity is increasing among the elderly, but more work is needed on devising age-appropriate indicators of high risk based on waist circumference.     

Waist Circumference,BMI, and Visceral Adipose Tissue in White Women and Women of African Descent

Although waist circumference (WC) is a marker of visceral adipose tissue (VAT), WC cut‐points are based on BMI category. We compared WC‐BMI and WC‐VAT relationships in blacks and whites. Combining data from five studies, BMI and WC were measured in 1,409 premenopausal women (148 white South Africans, 607 African‐Americans, 186 black South Africans, 445 West Africans, 23 black Africans living in United States). In three of five studies, participants had VAT measured by computerized tomography (n = 456). Compared to whites, blacks had higher BMI (29.6 ± 7.6 (mean ± s.d.) vs. 27.6 ± 6.6 kg/m², P = 0.001), similar WC (92 ± 16 vs. 90 ± 15 cm, P = 0.27) and lower VAT (64 ± 42 vs. 101 ± 59 cm², P < 0.001). The WC‐BMI relationship did not differ by race (blacks: β (s.e.) WC = 0.42 (.01), whites: β (s.e.) WC = 0.40 (0.01), P = 0.73). The WC‐VAT relationship was different in blacks and whites (blacks: β (s.e.) WC = 1.38 (0.11), whites: β (s.e.) WC = 3.18 (0.21), P < 0.001). Whites had a greater increase in VAT per unit increase in WC. WC‐BMI and WC‐VAT relationships did not differ among black populations. As WC‐BMI relationship did not differ by race, the same BMI‐based WC guidelines may be appropriate for black and white women. However, if WC is defined by VAT, race‐specific WC thresholds are required.     

Age‐ and Gender‐specific BMI in Terms of the Lowest Mortality in Japanese General Population

Objective: The primary purposes of our study were to establish age‐ and gender‐specific BMIs in terms of lowest mortality (risk nadir BMIs) for the Japanese population, and to then compare those to (i) BMIs for whites as determined by similar studies and to (ii) the official BMI guidelines. Methods and Procedures: A total of 32,060 men and 61,916 women aged 40–79 years underwent health check‐ups in Ibaraki prefecture, Japan, in 1993 and were followed through 2003. To determine the age‐ and gender‐specific risk nadir BMIs, coefficients and the lowest point from a quadratic model with transformed BMI were calculated by a Cox proportional hazard model. This included the quadratic term of 1/BMI and adjusted values (age, alcohol intake, and smoking status). Results: For both age and both gender categories, the relationship between all‐cause mortality risk and BMI categories are illustrated as U‐shaped curves. The risk nadir BMIs for men in the age groups of 40–59 and 60–79 years were 23.4 and 25.3 kg/m², respectively. Similarly, in women, the risk nadir BMIs were 21.6 and 23.4 kg/m², respectively. Discussion: Among the general Japanese population, the risk nadir BMI for the age group of 60–79 years was higher compared to the age group of 40–59 years, which was similar to the study for whites, and the age‐dependent risk nadir BMI differed from the official guidelines criteria. Our findings underscore the importance of weight control following appropriate indicators of body weight according to age.     

BMI,Waist Circumference,and Mortality According to Health Status in the Older Adult Population of Spain

Among the explanations proposed for the weak and inconsistent association between BMI and mortality in the elderly are the lack of adjustment for waist circumference (WC) and that the association varies with health status. This work examines the independent association of BMI and WC with mortality in older adults, and the influence of health status on this association. A cohort of 3,536 persons representative of the Spanish population aged ≥60 years was selected in 2000 and 2001, and followed prospectively until 2007. The analyses were performed with Cox models and adjusted for the main confounders. During follow‐up, 659 persons died (18.6% of the cohort). Before adjusting for WC, mortality in the upper quartile of BMI was 15% lower than in the lower quartile (hazard ratio (HR): 0.85; 95% confidence interval (CI): 0.66–1.08; P for linear trend = 0.076). After adjusting for WC, the association was even stronger, so that mortality in the upper quartile of BMI was 37% lower than in the lower quartile (HR: 0.63; 95% CI: 0.45–0.88; P for linear trend < 0.003). Before adjusting for BMI, no association was observed between WC and mortality. After adjusting for BMI, WC was positively associated with mortality (HR for upper vs. lower quartile of WC: 1.48; 95% CI: 1.07–2.05; P for linear trend = 0.008). These associations were mainly observed in those with limitations in mobility and agility. BMI has an inverse, and WC has a direct, independent association with mortality in older adults, particularly in those with worse health status.