In Germany, the reference system according to Kromeyer-Hauschild is usually used to define underweight, overweight and obesity in children and adolescents. International classification systems to describe prevalence rates are the reference systems of the World Health Organization (WHO) and the International Obesity Task Force (IOTF). This article discusses underweight, overweight and obesity prevalence among children and adolescents according to WHO and IOTF criteria using data from the second wave of the German Health Interview and Examination Survey for Children and Adolescents (KiGGS Wave 2, 2014-2017). According to the WHO reference system, the prevalence of underweight among 5- to 17-yearolds is 1.6%, the prevalence of overweight is 26.3 % (including obesity) and the prevalence of obesity is 8.8 %. According to IOTF, the prevalence of underweight among 3- to 17-year-olds is 10.0 %. The prevalence of overweight (including obesity) is 19.3 % and the prevalence of obesity is 4.7 %. From a public health point of view, underweight compared to overweight and obesity plays a rather minor role as an indicator of malnutrition in Germany. The prevalence of overweight according to WHO is three quarters higher and one quarter higher according to IOTF than the national reference. If the international reference systems are compared, the WHO prevalence is one third higher than IOTF prevalence. Over time, national and international reference systems do not indicate any further increase in prevalence of overweight and obesity, but they remain at a high level.