[Using three different screening methods to study overweight and simple obesity among children under age 7 in Ningbo city].

Objective: To investigate the occurrence of simple obesity among children under age 7 in Ningbo and to analyze the data regarding body mass index (BMI) from overweight screening under different standards.

Methods: Randomized cluster sampling was adopted and 64 038 children under 7 years old in Ningbo were chosen and their length/height and weight were measured but pathological and secondary obesity cases were excluded. According to the Standardized Height and Weight set by WHO, more than 10% referring to overweight and more than 20% referring to obesity. Moreover, results of this study were compared with growth standards with WHO's 2006 and IOTF standards.

Results: According to the Standardized Height and Weight set by WHO, the prevalence rates of overweight and obesity of children under age 7 were 4.25% and 2.88%. The ratio for boys were 4.45% and 3.01%, while for girls as 3.86% and 2.56%, with significant difference (P < 0.01). Data showed that the rates for overweight and obesity increased along with age, reaching 11.84% and 9.68% for boys and 10.14% and 9.46% for girls at the age of 6. The ratios of overweight/obesity among different age groups and sex were 1.15-1.94:1. The critical value for P85, P95 were lower than the standards set by WHO and IOTF. The rates for overweight and obesity for latter were 9.72%, 2.83% and 6.11%, 0.55% respectively.

Conclusion: Early childhood is the key period for obesity prevention, with boys in particular. Prevention and control for childhood obesity should be included in the programs for children's health. Value of classification standards for the BMI screening of overweight and obesity for children under age 7 should be established in no time.