Screening of central obesity among normal-weight children and adolescents in Shandong, China

The prevalence of central obesity in the total population has been reported in numerous studies. However, information on the prevalence of central obesity within normal-category BMI is scant. In the present study, we examined the profiles of central obesity among normal-weight children and adolescents. A total of 29 516 (14 226 boys and 15 290 girls) normal-weight children and adolescents (excluding underweight, overweight and obesity) aged 7-18 years were included in the final analysis. Central obesity was defined by the international age- and sex-specific cut-offs of waist circumference (WC) and threshold of waist:height ratio (WHtR ≥ 0·5). All subjects were classified into four groups (Q1-Q4) according to the age- and sex-specific quartiles of BMI, those in the upper fourth (Q4) were defined as 'high-normal BMI' and those in the lower fourth (Q1) were defined as 'low-normal BMI'. The prevalence of central obesity as measured by WC was 9·90 (95 % CI 9·41, 10·39) % for boys and 8·11 (95 % CI 7·68, 8·54) % for girls; by WHtR was 2·97 (95 % CI 2·69, 3·25) % for boys and 2·44 (95 % CI 2·20, 2·68) % for girls. Subjects in the Q4 group had a much higher prevalence of central obesity than their counterparts in the Q1 group (P < 0·01). Our findings suggest that the health risks of children with normal-weight central obesity may be missed when BMI is used alone as a measure; it is meaningful to include WC in clinical practice and to include the simple message 'Keep your waist to less than half your height'.