Objective and Methods: The aim of the present study is to repeat the 2002 and 2007 national studies, in order to monitor the trend in the prevalence of overweight and obesity in 6-12 year old children in Switzerland during this 5 respectively 10 year time period. Height and weight will be measured and used to calculate body mass index (BMI). BMI references form the Centers for Disease Control and Prevention will be used to determine the prevalence of underweight (< 5th percentile), overweight (≥ 85th and < 95th percentile) and obesity (≥ 95th percentile). Waist and hip circumference will be measured. Moreover, skinfold thicknesses and bioelectrical impedance analysis will be performed to calculate body fat percentage.