Relationship of Body Mass Index, Waist Circumference and Cardiovascular Risk Factors in Chinese Adult

Objective To compare the relative risk of waist circumference （WC） and/or BMI on cardiovascular risk factors. Methods A cross-sectional data of 41 087 adults （19 567 male and 21 520 female） from the 2002 China National Nutrition and Health Survey were examined. According to the obesity definition of WGOC （BMI, 24 kg/m^2 and 28 kg/m^2; WC, male 85 cm and 95 cm for male, 80 cm and 90 cm for female）, the study population were divided into 9 groups. The prevalence and odds ratio （ORs） of cardiovascular disease （CVD） risk factors （hypertension, high fasting plasma glucose and dyslipidemia） were compared among these 9 groups. Stepwise linear regression analyses were used to compare the likelihood of BMI and/or WC on CVD risk factors. Results Both the indexes levels and the odds ratios of CVD risk factors were significantly increased （decreased for HDL-C levels） along with the increase of WC and/or BMI, even when the effect of age, sex, income, education, sedentary activity and dietary factors were adjusted. The variances （R2） in CVD risk factors explained by WC only and BMI only were quite similar, but a little bit larger when WC and BMI were combined. The standard fl was higher of BMI when predicting systolic BP and was higher of WC when predicting TG, TC and HDL. Conclusions BMI and WC had independent effects on CVD risk factors and combination of BMI and WC would be more predictive. Findings from the present study provided substantive evidence for the WGOC recommendation of a combined use of BMI and WC classifications.

Report on Childhood Obesity in China (2) Verification of BMI Classification Reference for Overweight and Obesity in Chinese Children and Adolescents

Objective To verify Working Group for Obesity in China （WGOC） recommended body mass index （BMI） classification reference for overweight and obesity in Chinese children and adolescents using the data of 2002 China Nationwide Nutrition and Health Survey. Methods PediaWic metabolic syndrome （MetS） and abnormality of each risk factor for MetS were defined using the criteria for US adolescents. Definition of hyper-TC, LDL, and dyslipidemia in adults was applied as well. The average level and abnormality rate of the metabolic indicators were described by BMI percentiles and compared with general linear model analysis. Receiver operating characteristic analysis was used to summarize the potential of BMI to discriminate between the presence and absence of the abnormality of these indicators. Results There was neither significantly increasing nor significantly decreasing trend of biochemical parameter levels in low BMI percentile range （〈65th）. Slight increasing trend from the 75th and a significant increase were found when BMI≥85th percentile. In general, the prevalence of the examined risk factors varied slightly when BMI percentile〈75th, and substantial increases were consistently seen when BMI percentile≥75th. As an indicator of hyper-TG, hypertension and MetS, the sensitivity and specificity were equal at the point of BMI〈75th percentile, and the Youden＇s index of risk factors also reached peak point before 75th percentile except for MetS. When the BMI percentile was used as the screening indicator of MetS, Youden＇s index reached peak point at 85th percentile, just the point in the ROC graph that was nearest to the upper left comer. Conclusion The BMI classification reference for overweight and obesity recommended by WGOC is rational to predict and prevent health risks in Chinese children and adolescents. Lower screening cut-off points, such as 83th percentile or 80th percentile, should not be excluded when they are considered as overweight criteria in future intervention or prevention studies.

Waist Circumference Reference Values for Screening Cardiovascular Risk Factors in Chinese Children and Adolescents

Objectives To explore the optimal threshold values of waist circumference （WC） for detecting cardiovascular （CV） risk factors among Chinese children and adolescents. Methods Association of WC with CV risk factors was studied among 65 898 children aged 7-18 years whose data were pooled from nine previous studies in China. CV risk factors in this study included hypertension （blood pressure above 95 percentile levels）, dyslipidemia （with one or more of the following three indexes： TG ≥ 1.7 mmol/L, TC ≥ 5.18 mmol/L, and HDL-C ≤ 1.04 mmol/L） and elevated glucose level （fasting plasma glucose ≥5.6 mmol/L）. Receive-operating characteristic analysis （ROC） and logistic regression were employed to derive optimal age- and sex-specific waist circumference references for predicting CV risk factors. Results A slight increasing trend of CV risk factors was observed starting from the 75th percentile of waist circumference in the study population, while a remarkable increasing trend occurred from the 90th percentile. The optimal waist circumference thresholds for predicting high blood pressures were at the 75th percentile for both boys and girls, which was at the 90th percentiles for detecting at least two of the above three CV risk factors. In comparison with children with waist circumference below the 75th percentile, the odds ratio of two CV risk factors doubled among children with waist circumference between the 75th and the 90th percentile, and increased by 6 times among children with waist circumference above the 90th percentile. The trend of high blood pressure increasing with waist circumference remained significant after having been stratified by BMI category. Conclusion The 75th and the 90th percentiles of WC are the optimal cut-off points for predicting an increased and a substantially increased risk of CV factors in Chinese children and adolescents, respectively.

Report on Childhood Obesity in China (5) Body Weight, Body Dissatisfaction, and Depression Symptoms of Chinese Children Aged 9-10 Years

Objective To investigate the relationship between body weight, body dissatisfaction and depression symptoms among Chinese children. Methods The fasting body weight and height of the third and fourth grade students （n=3886, aged 9 or 10 years） from 20 schools in Beijing, China, were measured, and the students were asked to choose the figures of body image and to complete the self-reported children＇s depression inventory （CDI） questionnaire. Results The CDI Cronbach＇s alpha was 0.81. The total CDI score was 9.60±7.50, 13.2% of children （boys 16.7% vs girls 9.5%） were at risk of developing depression symptoms. Overweight girls, but not boys, had significantly higher total CDI score than their normal weight counteparts. Both obese girls and boys showed a higher negative self-esteem score. More than one fifth underweight girls still wanted to be thinner while more than one third obese boys still wanted to be heavier. Children who wanted to be thinner showed slightly higher scores of ineffectiveness and negative self-esteem. After introducing the body dissatisfaction into the model, overweight was still associated with total CDI score among girls and obesity was still associated with negative self-esteem among both boys and girls. Conclusion Overweight girls show a significantly higher depression symptom score than their normal weight counterparts, which maybe partially explained by body dissatisfaction. Obese boys and girls are both more likely to suffer from low self-esteem, which is partially explained by body dissatisfaction.

Report on Childhood Obesity in China (6) Evaluation of a Classroom-based Physical Activity Promotion Program

Objectives To evaluate the effect of Happy 10 program on the promotion of physical activity, physical growth and development of primary-school students, and on obesity control and prevention. Methods Two similar primary schools from one district of Beijing, China were selected, one as an intervention school and the other as a control school. Happy 10 program was implemented at least once every school day in the intervention school for two semesters, whereas no intervention was adopted in the control school. The information on energy expenditure and duration of physical activity was collected by a validated 7-day physical activity questionnaire. Height and weight were measured by trained investigators following the standardized procedure. Energy expenditure and intensity of each Happy 10 session was measured by a physical activity monitor. Results The average energy expenditure and duration of total physical activity per day among students in the intervention school increased significantly from 15.0 to 18.2 kcal/kg, and 2.8 to 3.3 h respectively, whereas the figures significantly decreased in the control school. There was a significant difference in change of weight and BMI between girls in the intervention and control school （2.4 kg vs 4.6 kg, -0.47 kg/m^2 vs 0.66 kg/m^2）. The prevalence of overweight and obesity in the intervention school decreased by 0.4%-5.6%, as compared to the increase by 0.6%-4.5% in the control school. The average energy expenditure and intensity per 10-minute session ranged from 25.0-35.1 kcal, 4.8-6.2 kcal/kg/h respectively in grades 1-5. Conclusion Happy 10 program provides a useful strategy to promote physical activity among school children and also plays a positive role in building up physical growth and development of girls.