INTRODUCTION: There is no agreement among researchers on adiposity indexes and on the best cutoff to define obesity.
OBJECTIVE: The objective of this study was to evaluate the validity of BMI and fat mass index (FMI) as indicators of obesity in 272 boys and 242 girls who were aged 3 to 5 years.
METHODS: Bioelectrical impedance analysis was used to calculate percentage fat mass (%FM) and FMI (fat mass/stature2). Boys and girls were considered obese when %FM was ≥ 25 and ≥ 30, respectively. Cutoffs of BMI (weight/stature2) and FMI were tested at 90th, 95th, and 97th percentiles.
RESULTS: There were strong, significant correlations between BMI or FMI and %FM, but there was no significant correlation between BMI or FMI and stature; therefore, both BMI and FMI are useful indexes to assess fatness and obesity. With the use of %FM as the criterion for obesity, however, the highest prevalence of obesity was found at the 90th percentile for both genders. BMI and FMI had high specificities and lower but variable sensitivities. FMI is associated with a level of sensitivity that is somewhat higher than that of BMI. Almost all children who were not obese were classified correctly, whereas many obese children were not correctly identified.
CONCLUSIONS: FMI is a specific indicator of childhood obesity, and at 90th percentile, it has moderately high sensitivity. BMI should be used with caution as an indicator of childhood obesity.
- Copyright © 2008 by the American Academy of Pediatrics