Introduction Due to the overweight and obesity epidemic, growth references based on recent data may no longer be appropriate for monitoring childhood body mass index (BMI) as they may underestimate the problem. Our aim is to determine the difference in signalling overweight and obesity between the use of up to date references and cut-offs for BMI according to the International Obesity Task Force (IOTF).

Methods The growth references for BMI were constructed using cross-sectional growth data from the Fifth Dutch Growth Study in 2009 (n=10 129). We plotted the IOTF cut-offs against the Dutch growth references for ages 2–18 y. Moreover, we compared the prevalence of overweight and obesity according to IOTF with respectively the +1.6 and +2.7 SD score (SDS) on the Dutch growth references. These SDS cut-offs correspond to a BMI of 25 and 30 kg/m² at age 18 y in the Third Dutch Growth Study in 1980, which was part of the sample to construct the IOTF cut-offs.

Results The IOTF cut-offs for overweight and obesity were lower than +1.6 and +2.7 SDS at all ages. The difference between IOTF and the cut-offs for SDS ranged from −1.8 to −2.5 SDS for overweight and −1.2 to −2.3 SDS for obesity.

Conclusion Using up to date population based references for BMI with recommended SDS cut-offs for Dutch children results in an underestimation of the problem. In countries with substantial overweight and obesity, we recommend using pre-epidemic references or cut-offs, such as proposed by the International Obesity Task Force.