Depending upon age, gender and geographical area, 3-20% of the children and young adolescents in Switzerland are overweight and 0-6% obese, using the criteria of the International Obesity Task Force. The most likely explanation for this increasing prevalence of overweight and obesity is a decline in physical activity, and hence diminished energy expenditure that is not matched by a corresponding reduction in energy intake. In this paper, we first review the epidemiological situation in Switzerland regarding the rising prevalence of obesity and the decline in physical activity, and then focus upon the environmental, social and cultural factors that predispose children to sedentary behaviours. Several of these socio-cultural factors and in particular television viewing and poor-parental model, confer early 'learned behaviours' for low physical activity which track throughout growth into adulthood, and which also predispose to the overconsumption of less healthy foods. It is time to focus on preventive strategies directed at curtailing these 'learned behaviours', that we have acquired during the transition from the stone-age to the chip-age, if we want to hold the current pandemic of obesity.