| Obesity is defined as excessive fat accumulation that may impair health. Body mass index(BMI) and waist circumference are the most practical indices for identifying obesity. This study aimed to explore the changes in the prevalence of overweight, obesity and central obesity, to evaluate the clinical utility of waist circumference and BMI categories in identifying the risk of metabolic disorders, and to compare waist circumferences in Chinese adults with impared glucose regulation(IGR) or newly diagnosed diabetes(NDM) and in their counterparts with normal glucose regulation(NGR) and estimated the hyperglycemia burden attributable to central obesity.Section 1. Ten-year Changes in the Prevalence of Overweight, Obesity and Central Obesity among the Chinese Adults in Urban Shanghai, 1998-2007 — Comparison of Two Cross-sectional SurveysObjective In China, obesity is expected to increase rapidly in both urban and rural areas. However, there have been no comprehensive reports on secular trends in obesity prevalence among Chinese adults in urban Shanghai, which is the largest city in southern China.Methods In 1998-2001 and again in 2007-2008, two independent population-based cross-sectional surveys were conducted in Shanghai to investigate the prevalence of metabolic disorders. These surveys obtained height, waist circumference(WC), and weight measurements for Chinese adults aged between 20 and 74 years who lived in urban communities. From the 1998-2001 survey, 4,894 participants(2,081 men and 2,813 women,mean age: 48.9 years) were recruited, and 4,395 participants(1,599 men and 2,796 women, mean age: 49.8 years) were recruited from the 2007-2008 survey. Using the World Health Organization criteria, overweight was defined as 25 kg/m2 ≤ BMI < 30 kg/m2 and obesity as BMI ≥ 30 kg/m2. Central obesity was defined as waist circumference ≥ 90 cm in men or ≥ 85 cm in women. The differences in prevalence of obesity, central obesity and overweight between the two surveys were tested using multivariable logistic regression analyses.Results Compared to the 1998–2001 survey, in the 2007–2008 survey the BMI distribution for men and the WC distribution for both genders is shifted significantly to the right along thex-axis(all P < 0.001). Over the ten years, the prevalence of combined overweight and obesity increased 24%(from 31.5% to 39.1%, P < 0.001) in men, but decreased 8%(from 27.3% to 25.0%; P < 0.01) in women. The prevalence of central obesity increased 40% in men(from 19.5% to 27.3%; P < 0.01), but the increase was not significant in women(15.0% to 17.1%; P =0.051). In the total population, only central obesity showed a significant change between the populations in the two surveys, increasing 29%(from 17.3% to 22.4%; P < 0.001).Conclusions Over this 10 year period, central obesity increased significantly in the Shanghai adult population. However, the prevalence of combined overweight and obesity was significantly increased in men but not in women.Section 2. Impact of Waist Circumference and Body Mass Index on Risk of Cardiometabolic Disorder and Cardiovascular Disease in Chinese Adults — A National Diabetes and Metabolic Disorders SurveyObjective We updated the prevalence of obesity and evaluated the clinical utility of separate and combined waist circumference(WC) or body mass index(BMI) category increments in identifying cardiometabolic disorder(CMD) and cardiovascular disease(CVD)risk in Chinese adults.Methods 46,024 participants aged ≥ 20 years, a nationally representative sample surveyed in 2007-2008, were included in this analysis. Taking the cutoffs recommended by the Chinese Joint Committee for Developing Chinese Guidelines(JCDCG) and the Working Group on Obesity in China(WGOC) into account, the participants were divided into four WC and four BMI groups in 0.5-SD increments around the mean, and 16 cross-tabulated combination groups of WC and BMI.Results 27.1%, 31.4%, and 12.2% of Chinese adults are centrally obese, overweight, or obese according to JCDCG and WGOC criteria. Multivariate regression analysis revealed that after adjustment for the confounding factors, WC groups were at higher risk of having DM than BMI groups for the same SD increment, the adjusted ORs(95% CIs) of having DM for WC Group IV vs. BMI Group IV were 1.88(1.57-2.28) vs. 1.19(0.99-1.44) in men and 1.73(1.47-2.02) vs. 1.10(0.94-1.29) in women; whereas BMI groups were at higher risk of having hypertension than WC groups, the adjusted ORs(95% CIs) of having hypertension for BMI Group IV vs. WC Group IV were 3.87(3.35-4.46) vs. 1.33(1.16-1.52) in men and 3.27(2.90-3.70) vs. 1.54(1.37-1.74) in women. The combination of WC and BMI categories was more likely to identify individuals with lower WC and lower BMI at CVD risk, even after the effects of CMD were controlled(all P<0.05).Conclusions Central obesity, overweight, and obesity are epidemic in Chinese adults. The combination of WC and BMI measures is superior to the separate indices in identifying CMD and CVD risk.Section 3. Contribution of Central Obesity to the Prediabetes and Diabetes Burden in Chinese Adults — A National Mathced Case—Control StudyObjective We examined waist circumferences in Chinese adults with IGR or NDM and in their counterparts with NGR and estimated the hyperglycemia burden attributable to centralobesity.Methods We selected 43,698 subjects(6909 IGR–NGR and 2867 NDM–NGR region-, sex-, and age-matched pairs) for this case–control analysis. IGR and NDM were identified using an oral glucose tolerance test. Central obesity was defined as waist circumference ≥ 90 cm(men) or ≥ 85 cm(women).Results The respective average waist circumferences(cm) of the prediabetes–NGR and NDM–NGR pairs were 85.4 vs. 82.0, 87.9 vs. 83.0(overall population); 88.4 vs. 85.0, 90.6 vs. 85.6(men); 83.3 vs. 80.0, 85.7 vs. 80.8(women); 86.6 vs. 83.4, 89.0 vs. 84.6(northern population); 83.0 vs. 79.3, 85.9 vs. 80.1(southern population)(P < 0.001). Using the group without central obesity and its related metabolic disorders as reference, the corresponding odd ratios of prediabetes or NDM for groups with central obesity, central obesity and elevated BP, central obesity and elevated TG, and central obesity with elevated BP and elevated TG were: 1.71, 2.79, 3.25, 5.48(overall population); 1.64, 2.54, 3.07, 5.21(northern population); and 1.83, 3.47, 3.63, 5.97(southern population)(P < 0.05). The respective weighted estimates of overall, northern, and southern population attributable fraction of prediabetes and NDM to central obesity and its related metabolic disorders were 33.4%, 35.9%, and 28.0%.Conclusions In Chinese adults, about one-third of prediabetes and NDM cases is attributable to central obesity and its related metabolic disorders according to the currently stated criteria. |
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