Liu et al. BMC Public Health 2010, 10:82 http://www.biomedcentral.com/1471-2458/10/82 North and South of the country. Optimal age- and gen- der-specific cut-off points for waist circumference to predict cardiovascular risk factors clustering are also proposed. Waist circumference percentiles should be updated in different countries consistent with changes in overall body size due to changes in environmental factors. Most importantly, standardized methodology should be used for the development of international waist circumference cut-off points to diagnose cardio- vascular risk factors clustering. Acknowledgements This study was funded by The United Nations Children’s Fund. Author details 1National Institute for Nutrition and Food Safety, China Center for Disease Control and Prevention, Beijing, China. 2Institute of Health and Biomedical Innovation, Queensland University of Technology, Queensland, Australia. 3Guangzhou Center for Disease Control and Prevention, Guangzhou, China. 4Liaoyang Center for Disease Control and Prevention, Liaoyang, China. Authors’ contributions AL participated in the design of the study, collected data, performed the statistical analysis, and drafted the manuscript. APH helped to draft the manuscript and interpret the results. XH participated in the design of the study, collected the data and helped to interpret the results. YL collected the data and helped to perform the statistical analysis. LD participated in the coordination of the study, collected and entered the data, and helped to interpret the results. YX participated in the coordination of the study, collected and entered the data, and helped to interpret the results. NMB helped to draft the manuscript. GM conceived of the study, participated in its design and coordination, helped to perform the statistical analysis and draft the manuscript. All authors read and approved the final manuscript. Competing interests The authors declare that they have no competing interests. Received: 7 June 2009 Accepted: 19 February 2010 Published: 19 February 2010 References 1. Booth ML, Dobbins T, Okely AD, Denney-Wilson E, Hardy LL: Trends in the prevalence of overweight and obesity among young Australians, 1997, and 2004. Obesity 2007, 15:1089-1095. 2. Magarey AM, Daniels L, Boulton T: Prevalence of overweight and obesity in Australian children and adolescents: reassessment of 1985 and 1995 data against new standard international definitions. Med J Aust 2001, 174:561-564. 3. National Center for Health Statistics: Health, United States, 2004- with chartbook on trends in the health of Americans Maryland: Hyattsville 2004. 4. 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