At risk or not: Comparing normative and criterion-referenced Body Mass Index standards among Mexican American children

Most childhood obesity research has classified participants by normative standards for Body Mass Index (BMI) through population percentiles or values corresponding to overweight adults (World Health Organization (WHO), Centers for Disease Control and Prevention (CDC) and the International Obesity Task Force (IOTF)). In 2006, criterion-referenced standards (FitnessGram) were developed (revised in 2010) which directly associate BMI values with adverse health outcomes. This study assessed agreement between normative and criterion-referenced standards. Participants included 653 Mexican American 3rd to 5th graders living in the U.S.-Mexico border area who participated in a health promotion project. At baseline, agreement was compared between normative and criterion-referenced classifications. At follow-up, agreement between classifications on changes (e.g., from overweight to healthy weight) was assessed. According to FitnessGram standards, 53.0% of participants were overweight or obese at baseline. Compared to FitnessGram, the IOTF and CDC standards classified 15% fewer participants as obese/high risk. The WHO standards were closely related to FitnessGram (kappa=.925) and showed significantly greater agreement with FitnessGram than the CDC (kappa=.925 versus 0.722, p < .001) and IOTF standards (kappa=.925 versus .682, p < .001). Compared to the FitnessGram (8.9%), the WHO and CDC (8.6%) were similar, but IOTF standards lower (6.5%) in how many children improved following the health program. Despite acceptable agreement between the different indices, several normative classifications may underestimate the proportion of children who are at risk for BMI-related adverse health consequences.