The MyMovez project investigates how health campaigns can best be implemented among youth. We focus on promoting a healthy lifestyle among 9 to 15 year-olds. During this phase in life, important habits are being formed regarding eating and drinking, physical activity, and media use. To reveal the success and fail factors of health campaigns, we test several mobile health campaigns among 1.000 children and adolescents in a period of three years, and we will investigate the short and long-term effects on their eating and drinking, physical activity and media behaviors. At the core of the project is the power of youth’s social networks. Research shows that the social environment has great influence on a young person’s lifestyle: e.g. dietary intake, physical activity, and media use. In order to get a closer look into the lifestyle of the target group, the investigators created the Wearable Lab. The Wearable Lab consists of a smartphone in combination with an activity-tracking bracelet. The smartphone includes an application (the MyMovez app) that on the one hand collects health-related data from the participants, for example through daily quizzes, photo’s, location tracking and message board conversations. On the other hand, the app can spread health messages and campaigns. The activity-tracker measures the number of steps taken to get an impression of participant’s physical activity. In this presentation, Thabo will present a couple of studies in the first phase of the project on the basis of the physical activity data. First he will show the innovative features of the wearable lab and how they helped us answer new research questions. Second, he will dive into the social networks of the primary and secondary classrooms and show how physical activity spreads in social network. Lastly, he will illustrate the next phase of the project by showing a recently conducted pilot studies in which specific pupils received the task to promote physical activity among their peers.