Childhood obesity: different definition criteria, different prevalence rate

Background. Evaluate the influence of reference growth curves on determination of prevalence of obesity in children and particularly compare two indicators most commonly used, overweight (OW%) and body mass index (BMI centile), measured in the same population. Methods. Design: cross-sectional study. Subjects: 40,068 children (19,892 males, 20,176 females) aged from 3 to 17 years. Results. The results obtained in this study show different prevalence rates according to the indicators used to define childhood obesity and according to the reference curves adopted. When Tanner-Whitehouse curves were used, prevalence peaked at age 9-13 years in males and age 8-14 years in females, with rates of up to 18%. When using our own curves to calculate ideal weight, the peak prevalence of obesity was at 12 years in males and 10 years in females, with prevalence rates of 11.8 and 13.7%, respectively. The prevalence of obesity, calculated using the BMI 90th percentile as the cut-off, ranged from 8 to 12%, with rates similar to those observed with OW% in children aged from 8 to 17 years, whereas the differences were greater in children aged from 3 to 8 (2.1% with OW% and 10.24% with BMI centile at 3 years). Conclusions. Prevalence rates are influenced by the reference curves used and the obesity indicator adopted. It would be desirable for epidemiological studies to use the same indicator, the same cut-off and, whenever possible, recent reference curves suitable for the particular population surveyed.