Abstract
Background/Aims The aim of the study was to examine the prevalence of obesity and extreme obesity in school-aged children using three classifications based on body mass index (BMI): BMI percentile, percentage above the 95th percentile and Z score, and the association of BMI stratification with elevated blood pressure.
Methods This was a retrospective study of 117,618 children aged 6–17 years receiving well-child care in Kaiser Permanente Northern California between July 2007 and December 2010. Blood pressure, BMI and other data were extracted from electronic records.
Results The prevalence of BMI >95th percentile ranged from 14.5% (4,395 of 30,235) in whites and 14.3% (2,287 of 16,033) in Asians to 22.3% (1,809 of 8,124) in blacks and 25.8% (5,734 of 22,187) in Hispanics. For boys, the highest prevalence was in Hispanics (29.2%, 3,346 of 11,452), followed by blacks (21.0%, 879 of 4,193); for girls, the highest prevalence was in blacks (23.7%, 930 of 3,931) and then Hispanics (22.2%, 2,388 of 10,735). For extreme obesity, a threshold of BMI ≥120% of the 95th BMI percentile identified the largest proportion of children (5.6%, 6,532 of 117,618) compared to BMI ≥99th percentile (3.8%, 4,488 of 117,618) and BMI Z score ≥3.0 (0.1%, 83 of 117,618). Stratification of BMI by percentage above the 95th percentile demonstrated a graded relationship between obesity severity and risk of elevated blood pressure.
Conclusions The prevalence of obesity and extreme obesity in children varied by age, gender and race/ethnicity, with the highest prevalence among Hispanics followed by black children. Compared to BMI thresholds based on the 99th BMI percentile or BMI Z score of 3, classification by BMI ≥120% of the 95th BMI percentile identified a greater percentage of severely obese children in whom additional health risk-stratification was achieved by further categorizing based on percentage above the 95th BMI percentile. This classification approach may be useful for obesity management in clinical practice, public health surveillance, and research.
