[Geographic and population difference of BMI in Chinese school-age youth]

By analyzing the group variations of Chinese school-aged youth, to gather scientific bases for establishing a screening norm for obesity.

More than 228,250 students aged 6 through 18 years participated in the 2000 National Surveillance on Students Health and Physical Fitness were enrolled as subjects, and were divided into various groups. The P(5), P(50) and P(95) of BMI were calculated and compared.

The differences of BMI among various groups were mainly reflected in the P95 high level of BMI, e.g., the means of BMI of boys aged 13 in large cities and in relatively underdeveloped rural areas were 25.7 and 21.1 with a difference of 4.6, and 22.8 and 20.3 for girls aged 11 with a difference of 2.5. Evident north-south differences were also found, especially during adolescent growth spurt. The means of BMI of those lived in the north and south China were 22.3 and 21.0 for girls aged 11 (difference 1.3), and 25.4 and 23.5 for boys aged 14 (difference 1.9), respectively. These findings clearly showed that much more obese youth exist in the metropolis than in the rural areas, and in the north than in the south China. The difference in BMI between the developed areas and developing areas could be found in early school ages. They were 22.5 and 16.7 for boys aged 7, and 19.8 and 16.7 for girls aged 7, respectively, which is a dominant difference among Chinese youth groups. However, that the BMI differences in the P(5) level were not as evident as in the high level means that malnutrition and under-weight were still popular in all Chinese youth groups.

In making a national norm for screening obesity in China, we'd better take high-level growth population as reference, to adapt the secular growth changes of Chinese youth. However, the huge urban-rural, north-south, developed-developing differences shown in this study should also be taken into full consideration, in order to make the screen norm be accepted by most of the Chinese youth groups.