Objective To study the relationship between overweight, obesity and blood pressure among children living in urban Beijing. Methods A total of 4 267 pupils aged 9～10 years were randomly selected. Overweight and obesity were defined by age and sex specific BMI classification reference for Chinese children. Hypertension was defined by age, sex and height specific reference for US children. Results The prevalence of overweight and obesity in boys was 19.4% and 21.2%, in girls was 10.9% and 12.1%, respectively. Mean levels of systolic blood pressure (SBP) and diastolic blood pressure (DBP) have significant different between all study group. The total prevalence of high blood pressure (HBP) was 16.1% for boys and 15.2% for girls, while it was 36.4% and 41.3% among obese boys and girls, respectively. The prevalence of high systolic blood pressure (HSBP), high diastolic blood pressure (HDBP)and HBP gradually increased as weight increased. Compared with the normal weight group, OR(95%CI) for HBP of overweight and obese children were 2.6 (2.1～3.3) and 5.8 (4.7～7.0), respectively. Conclusion Obesity is positive correlation with hypertension in children aged 9～10years of Beijing, and the risk of hypertension was increased with their body weight.

At present, methods of water-intake survey include government, industry, sector statistics data, dietary survey (24 hours dietary recall, dietary record and food frequency questionnaire), fluid intake survey (retrospective fluid-intake questionnaire, 1-5 days 24 hours fluid-intake survey, 7 days 24 hours fluid-intake record), weighing method with the food composition table, weighing method, duplicate portion method and chemical analysis, and so on. The method of 7 days 24 hours fluid-intake record is an internationally recognized and authoritative method for fluid-intake survey with the highest accuracy, which can reflect the differences of fluid intake between working and non-working days, and can obtain detailed data on behaviors and patterns of fluid water, such as the time, types and places of fluid intake. The method of combining weighing method, duplicate portion method and chemical analysis is used to analyze water intake from food with the highest accuracy, which can be used in an extensive range of population and areas, but with high cost and complex operating steps. It is of great practical significance to compare and evaluate the advantages and disadvantages of different methods about water-intake survey, which will be helpful for researchers to choose appropriate methods for water-intake survey to obtain accurate and representative data in various areas, different population, and complex circumstances.