Distribution of body mass index and the prevalence changes of overweight and obesity among adolescents in Shandong, China from 1985 to 2005

BACKGROUND: There is strong evidence of a positive secular trend in physical growth and body mass index (BMI) in most of the world over the last 20 years. However, no studies on this trend have been reported in Shandong Province, China. AIM: The present study assessed the secular trend in BMI in Shandong Province during the past 20 years and the prevalence of overweight and obesity among adolescents. SUBJECTS AND METHODS: The BMI of adolescents aged 7-18 was calculated using data from three national surveys on students' constitution and health carried out by the government in 1985, 1995 and 2005 in Shandong Province, China. The distribution of BMI was reported, and the prevalence of overweight and obesity were obtained according to the screening criteria of overweight and obesity for Chinese students using BMI. RESULTS: In the past 20 years, the P(50) (percentile 50) of BMI increased rapidly. The average increments of BMI were 2.05 kg m(-2) (Urban male), 1.08 kg m(-2) (Urban female), 1.11 kg m(-2) (Rural male) and 0.57 kg m(-2) (Rural female). The prevalence of overweight and obesity increased rapidly: for overweight from 3.08% (Urban male), 2.67% (Urban female), 0.74% (Rural male) and 1.50% (Rural female) in 1985 to 17.52% (Urban male), 10.56% (Urban female), 11.06% (Rural male) and 7.01% (Rural female) in 2005; and for obesity from 0.52% (Urban male), 0.36% (Urban female), 0.03% (Rural male) and 0.11% (Rural female) in 1985 to 14.50% (Urban male), 6.79% (Urban female), 7.11% (Rural male) and 4.71% (Rural female) in 2005. CONCLUSION: The average value of BMI has increased over time; overweight and obesity among adolescents has become a serious public health problem. Comprehensive evidence-based strategies of intervention should be introduced, including periodic monitoring.