Increasing trends in waist circumference and abdominal obesity among US adults

Objective: Some studies have shown that abdominal obesity may be a better predictor than overall obesity for disease risks and all‐cause mortality. This study sought to examine the recent trends in waist circumference (WC) among adults in the United States. Research Methods and Procedures: Data from the National Health and Nutrition Examination Survey during 1988–1994, 1999–2000, 2001–2002, and 2003–2004 were analyzed to estimate the trends in the mean WC and the prevalence of abdominal obesity. Pooled t tests were used to test the differences in estimates between two time periods. Results: Between the periods of 1988–1994 and 2003–2004, the age‐adjusted mean WC increased from 96.0 cm to 100.4 cm among men (p < 0.001) and from 89.0 cm to 94.0 cm among women (p < 0.001); the age‐adjusted prevalence of abdominal obesity increased from 29.5% to 42.4% among men (p < 0.001) and from 47.0% to 61.3% among women (p < 0.001). Between the periods of 1999–2000 and 2003–2004, a significant increase occurred in mean WC only among men (from 99.0 cm to 100.4 cm; p = 0.03) and in the prevalence of abdominal obesity among both men (from 37.0% to 42.2%; p = 0.03) and women (from 55.3% to 61.3%; p = 0.04). People with a BMI of 25 to 29 kg/m² had a greater relative increase in abdominal obesity. Discussion: The mean WC and the prevalence of abdominal obesity among U.S. adults have increased continuously during the past 15 years. Over one‐half of U.S. adults had abdominal obesity in the period of 2003–2004.     

DNA methylation and obesity traits: An epigenome-wide association study. The REGICOR study

Obesity is associated with increased risk of several diseases and has become epidemic. Obesity is highly heritable but the genetic variants identified by genome-wide association studies explain only limited variability. Epigenetics could contribute to explain the missing variability. The study aim was to discover differential methylation patterns related to obesity. We designed an epigenome-wide association study with a discovery phase in a subsample of 641 REGICOR study participants, validated by analysis of 2,515 participants in the Framingham Offspring Study. Blood DNA methylation was assessed using Illumina HumanMethylation450 BeadChip. Next, we meta-analyzed the data using the fixed effects method and performed a functional and pathway analysis using the Ingenuity Pathway Analysis software. We were able to validate 94 CpGs associated with body mass index (BMI) and 49 CpGs associated with waist circumference, located in 95 loci. In addition, we newly discovered 70 CpGs associated with BMI and 33 CpGs related to waist circumference. These CpGs explained 25.94% and 29.22% of the variability of BMI and waist circumference, respectively, in the REGICOR sample. We also evaluated 65 of the 95 validated loci in the GIANT genome-wide association data; 10 of them had Tag SNPs associated with BMI. The top-ranked diseases and functions identified in the functional and pathway analysis were neurologic, psychological, endocrine, and metabolic.     

Genetic and Environmental Influences on Body‐Fat Measures among African‐American Twins

Objective: To investigate the genetic and environmental influences on body‐fat measures including waist circumference (WC), waist‐to‐hip ratio (WHR), and body mass index (BMI) among African‐American men and women. Research Methods and Procedures: Measurements were taken as part of the Carolina African American Twin Study of Aging. This sample currently comprises 146 same‐sex African‐American twins with an average age of 50 years (range, 22 to 88 years). This analysis included 26 monozygotic and 29 dizygotic men and 45 monozygotic and 46 dizygotic women. Maximum likelihood quantitative genetic analysis was used. Results: In men, additive genetic effects accounted for 77% of the variance in WC, 59% in WHR, and 89% in BMI. In women, additive genetic effects accounted for 76% of the variance in WC, 56% in WHR, and 73% in BMI. The remaining variance in both men and women was attributed to unique environmental effects (WC, 21%; WHR, 36%; BMI, 11% in men and WC, 22%; WHR, 38%; BMI, 27% in women) and age (WC, 2%; WHR, 5% in men and WC, 2%; WHR, 6% in women). When BMI was controlled in the analysis of WC and WHR, it accounted for a portion of the genetic and environmental variance in WHR and over one‐half of the genetic and environmental variance in WC. Discussion: There are both genetic and environmental influences on WC, WHR, and BMI, and independent of BMI, there are genetic and environmental effects on WC and WHR among both genders. The results from this African‐American twin sample are similar to findings among white twin samples.     

Sex,Race/Ethnicity,Socioeconomic Status,and BMI in Relation to Self‐Perception of Overweight

Objective: To compare the self‐perception of overweight in the study population according to sex, race/ethnicity, and socioeconomic status and to compare the self‐perception of overweight among individuals classified as normal weight, overweight, and obese. Research Methods and Procedures: Data from 5440 adults who participated in the 1994 to 1996 Continuing Survey of Food Intakes by Individuals and the Diet and Health Knowledge Survey conducted by the U.S. Department of Agriculture were analyzed. Data for analysis included self‐perceived weight status, self‐reported weight and height, and demographic and socioeconomic data. Underweight individuals, defined as those with a body mass index <18.5 kg/m², were excluded from the analysis. Results: Self‐perception of overweight was more common in women compared with men and in whites compared with blacks or Hispanics. Both the correct and incorrect perception of overweight was more common in normal weight and overweight white women compared with black women. More overweight and obese white men correctly perceived their overweight status compared with black men. Multiple logistic regression showed that the odds ratio of perceived overweight was significantly higher in women, whites, and individuals with higher body mass index, higher income, and higher education. Discussion: Self‐perceived overweight varied by sex, race/ethnicity, and socioeconomic status. Erroneous perception of body weight may have important health and behavioral implications. In particular, a considerable proportion of overweight men may be at risk of obesity if they continue to perceive themselves as having normal weight.     

Low molecular weight adiponectin negatively correlates with the waist circumference and monocytic IL-6 release

Adiponectin circulates as trimer (LMW), hexamer (MMW) and high molecular weight multimer (HMW) but the distribution and effects of these isoforms have not been studied in detail. Monocytes were isolated from normal weight and overweight controls and patients with type 2 diabetes mellitus (T2D) and monocytic release of IL-6 positively correlated with the body mass index (BMI). HMW-adiponectin further enhanced and LMW-adiponectin reduced IL-6 release in monocytes. Systemic total adiponectin, and the HMW isoform were not different in these groups but MMW-adiponectin was lower in T2D, and LMW-adiponectin was reduced in the obese and T2D. Circulating LMW-adiponectin negatively correlated to monocytic IL-6 release. Systemic IL-6 was higher in the obese control group and T2D, respectively, but did not correlate with monocytic IL-6 secretion. Therefore, the current study indicates that HMW-adiponectin exerts pro- and LMW-adiponectin antiinflammatory effects and reduced LMW-adiponectin in obesity may partly contribute to elevated monocytic IL-6 release.     

Overall and central obesity and risk of type 2 diabetes in U.S. black women

Objective: Obesity has risen to epidemic proportions in the United States, leading to an emerging epidemic of type 2 diabetes. African‐American women are disproportionately affected by both conditions. While an association of overall obesity with increasing risk of diabetes has been documented in black women, the effect of fat distribution, specifically abdominal obesity, has not been studied. We examined the association of BMI, abdominal obesity, and weight gain with risk of type 2 diabetes. Research Methods and Procedures: During eight years of follow‐up of 49,766 women from the Black Women's Health Study, 2472 incident cases of diabetes occurred. Cox proportional hazard models were used to estimate incidence rate ratios (IRRs), with control for age, physical activity, family history of diabetes, cigarette smoking, years of education, and time period of data collection. Results: Sixty‐one percent of participants had a BMI ≥25 kg/m² (WHO definition of overweight). Compared with a BMI of <23 kg/m², the IRR for a BMI of >45 kg/m² was 23 (95% confidence interval, 17.0 to 31.0). The IRR for the highest quintile of waist‐to‐hip ratio relative to the lowest was 2.3 (95% confidence interval, 2.0 to 2.7) after control for BMI. Furthermore, at every level of BMI, an increased risk was observed for high waist‐to‐hip ratio relative to low. Discussion: Central obesity, as well as overall obesity, is a strong risk factor for diabetes in African‐American women. Efforts to reduce the prevalence of obesity in African‐American women are of paramount importance.     

Utility‐based quality of life associated with overweight and obesity: The australian diabetes,obesity, and lifestyle study

Objective:

This study aimed to estimate utility‐based quality of life (UQoL) differences between healthy body weight and excess body weight categories.

Design and Methods:

Cross‐sectional analysis of 10,959 adults, participating in baseline data collection of the nationally representative Australian Diabetes, Obesity, and Lifestyle (AusDiab) Study was undertaken. Height and weight were measured by trained personnel. Body weight categories were assigned as healthy weight, overweight, and obesity subclasses I, II and III. UQoL was assessed using the SF‐6D, which captures physical functioning, role limitation, social functioning, pain, mental health, and vitality on a score of 0.00–1.00 (worst‐best). The relationship between body weight categories and UQoL was assessed using linear regression, adjusting for age, sex, education, and smoking.

Results:

Relative to the healthy weight group (mean UQoL score 0.77), mean adjusted UQoL differences (95% confidence intervals) were 0.001 (?0.008, 0.010) for overweight, ?0.012 (?0.022, ?0.001) for class‐I obese, ?0.020 (?0.041, 0.001) for class‐II obese, and ?0.069 (?0.099, ?0.039) for class‐III obese groups. Adding metabolic syndrome markers to the covariates had little impact on these differences.

Conclusion:

Results confirmed an inverse dose–response relationship between body weight and UQoL in this study of Australian adults. This highlights the need to incorporate UQoL measures which are sensitive to the subclasses of obesity when evaluating obesity interventions.

     

Optimal body weight for health and longevity: bridging basic,clinical, and population research

Excess body weight and adiposity cause insulin resistance, inflammation, and numerous other alterations in metabolic and hormonal factors that promote atherosclerosis, tumorigenesis, neurodegeneration, and aging. Studies in both animals and humans have demonstrated a beneficial role of dietary restriction and leanness in promoting health and longevity. Epidemiological studies have found strong direct associations between increasing body mass index (BMI) and risks of developing type 2 diabetes, cardiovascular disease, and several types of cancer, beginning from BMI of 20–21 kg m⁻². Although a recent meta-analysis suggests that overweight individuals have significantly lower overall mortality than normal-weight individuals, these data are likely to be an artifact produced by serious methodological problems, especially confounding by smoking, reverse causation due to existing chronic disease, and nonspecific loss of lean mass and function in the frail elderly. From a clinical and public health point of view, maintaining a healthy weight through diet and physical activity should remain the cornerstone in the prevention of chronic diseases and the promotion of healthy aging.     

Body mass index,waist circumference and employment: Evidence from older Irish adults

Data from the first wave of the Irish Longitudinal Study on Ageing are used to examine the relationship between fatness and obesity and employment status among older Irish adults. Employment status is regressed on one of the following measures of fatness: BMI and waist circumference entered linearly as continuous variables and obesity as a categorical variable defined using both BMI and waist circumference. Controls for demographic and socioeconomic characteristics, socioeconomic characteristics in childhood and physical, mental and behavioural health are also included. The regression results for women indicate that all measures of fatness are negatively associated with the probability of being employed and that the employment elasticity associated with waist circumference is larger than the elasticity associated with BMI. The results for men indicate that employment is not significantly associated with BMI and waist circumference when these are entered linearly in the regression, but it is significantly and negatively associated with obesity defined either using BMI or waist circumference as categorical variables. The results also indicate that the negative association between obesity and employment status is larger among women. For example, the probability of being employed for the obese category defined using BMI is around 8 percentage points lower for women and 5 percentage points lower for men.     

Effect of Smoking on the Paradox of High Waist‐to‐Hip Ratio and Low Body Mass Index

Objective: Research on diabetes mellitus (DM) indicates that people with a low body mass index (BMI) but a high waist‐to‐hip ratio (WHR) are in a particularly high‐risk group. The purpose of this study was to investigate the prevalence of and the effect of smoking on this paradoxical relationship. Research Methods and Procedures: Our study sample consisted of 3450 men and 4250 women who had participated in the Korean Nationwide Health Examination Survey. We divided the study sample into tertiles (low, medium, and high), according to the level of WHR and of BMI, which yielded nine different combinations. Individuals exhibiting so‐called paradox A had the highest WHR and the lowest BMI. Results: The prevalence of paradox A was 4.7% for men and 3.8% for women. The overall agreement of WHR and BMI groups was poor [for men: κ = 0.31 and 95% confidence interval (CI) = 0.29 to 0.34; for women: κ = 0.39 and 95% CI = 0.37 to 0.42 for women]. The odds ratios for subjects having paradox A were estimated using a logistic regression model after adjusting for age, age², height, education, smoking, use of alcohol, and exercise. The risk for paradox A among current smokers was 2.1‐fold (95% CI, 1.5 to 3.0) higher for men and 2.5‐fold (95% CI, 1.6 to 3.9) higher for women than for nonsmokers, after adjusting for age and covariates. Discussion: Cigarette smoking may increase the risk of paradox A. The findings of this study should be crossvalidated to different populations.     

Brief communication: Body mass index,body adiposity index,and percent body fat in asians

Human obesity is a growing epidemic throughout the world. Body mass index (BMI) is commonly used as a good indicator of obesity. Body adiposity index (BAI = hip circumference (cm)/stature (m)^1.5 ? 18), as a new surrogate measure, has been proposed recently as an alternative to BMI. This study, for the first time, compares BMI and BAI for predicting percent body fat (PBF; estimated from skinfolds) in a sample of 302 Buryat adults (148 men and 154 women) living in China. The BMI and BAI were strongly correlated with PBF in both men and women. The correlation coefficient between BMI and PBF was higher than that between BAI and PBF for both sexes. For the linear regression analysis, BMI better predicted PBF in both men and women; the variation around the regression lines for each sex was greater for BAI comparisons. For the receiver operating characteristic (ROC) analysis, the area under the ROC curve for BMI was higher than that for BAI for each sex, which suggests that the discriminatory capacity of the BMI is higher than the one of BAI. Taken together, we conclude that BMI is a more reliable indicator of PBF derived from skinfold thickness in adult Buryats. Am J Phys Anthropol 152:294–299, 2013. © 2013 Wiley Periodicals, Inc.     

Variations in Body Composition and Plasma Lipids in Response to a High‐Carbohydrate Diet

Objective: To examine the extent to which variations in body composition modulate changes in the lipid profile in response to the ad libitum consumption of a diet rich in carbohydrates (CHOs) (high‐CHO diet: 58% of energy as CHOs) or high in fat and in monounsaturated fatty acids (MUFAs) (high‐MUFA diet: 40% of energy as fat, 23% as MUFAs). Research Methods and Procedures: Sixty‐three men were randomly assigned to one of the two diets that they consumed for 6 to 7 weeks. Body composition and fasting plasma lipid levels were measured at the beginning and the end of the dietary intervention. Results: The high‐CHO and high‐MUFA diets induced significant and comparable reductions in body weight and waist circumference. These changes were accompanied by significant and comparable (p < 0.01) reductions in total plasma cholesterol and low‐density lipoprotein cholesterol levels. However, the high‐MUFA diet had more beneficial effects on plasma triglyceride concentrations (p < 0.01) and on plasma high‐density lipoprotein cholesterol levels (p = 0.02) compared with the high‐CHO diet. Diet‐induced changes in waist circumference were significantly associated with changes in low‐density lipoprotein cholesterol levels in the high‐CHO group (r = 0.39, p = 0.03) but not in the high‐MUFA group (r = 0.16, p = 0.38). Discussion: Improvements in plasma lipids induced by the ad libitum consumption of a high‐CHO diet seem to be partly mediated by changes in body weight, whereas lipid changes induced by the high‐MUFA diet seem to be independent of changes in body weight.     

Effect of Energy‐Reduced Diets High in Dairy Products and Fiber on Weight Loss in Obese Adults

Objective: Studies suggest that high‐dairy and high‐fiber/low‐glycemic index diets may facilitate weight loss, but data are conflicting. The effects on weight loss and body fat of a high‐dairy diet and a diet high in dairy and fiber and low in glycemic index were compared with a standard diet. Research Methods and Procedures: Ninety obese subjects were recruited into a randomized trial of three diets designed to provide a calorie deficit of 500 calories/d over a 48‐week period. The study compared a moderate (not low)‐calcium diet with a high‐calcium diet. Results: Seventy‐two subjects completed the study. Significant weight and fat loss occurred with all three diets. A diet with 1400 mg of calcium did not result in greater weight (11.8 ± 6.1 kg) or fat (9.0 ± 6.0 kg) loss than a diet with 800 mg of calcium (10.0 ± 6.8 and 7.5 ± 6.6 kg, respectively). A diet with 1400 mg of calcium, increased fiber content, and fewer high‐glycemic index foods did not result in greater weight (10.6 ± 6.8 kg) or fat (8.5 ± 7.8 kg) loss than the standard diet with 800 mg of calcium. Lipid profile, high‐sensitivity C‐reactive protein, leptin, fasting glucose, and insulin improved significantly, but there were no significant differences between the experimental diets and the control diet. Discussion: We found no evidence that diets higher than 800 mg of calcium in dairy products or higher in fiber and lower in glycemic index enhance weight reduction beyond what is seen with calorie restriction alone.