Diagnosis of overweight in adolescents aged: comparative study of different criteria for Body Mass Index

Objective In an attempt to simplify the screening process for detecting obe sity in adolescence, the performance of different cutoff values for body ma ss index (BMI) was assessed in a population-based cohort irt Southern Brazi l. Methods A total of 493 adolescents aged 15-16 years who lived in the city o f Pelotas, Brazil, were studied. Obesity was defined according to the WHO c riteria taking into account age and sex (a BMI equal to or greater than the 85(th) percentile of the NHANES I reference, plus subscapular and triceps skinfold equal to or. greater than the 90(th) percentile of the same refere nce). Different BMI cutoff values were used to assess their specificity and sensitivity. Results For boys, BMI greater than or equal to 25 kg/m(2) showed the best p erformance for detecting obesity, with a sensitivity of 90% and only 5% of false positives. The Brazilian proposed criteria that was used had 100% sen sitivity but up to 23% of false positives. Higher cutoff values were also t ested but there was a slight increase in specificity accompanied by a marke d reduction in sensitivity. Conclusions The BMI cutoff of 25 kg/m(2) presented the best performance for screening obesity in the studied sample, and it is recommended for adolesc ents aged 15 and more in populations with similar characteristics. It provi des a single cutoff value to be used in primary health services, eliminatin g the need for age and sex-specific values and skinfold measurements, and i t is also consistent with the cutoff value proposed to identifying overweig ht adults.