Abstract The focus within this policy area was on the effectiveness of available school-based policies that aim at increasing energy expenditure. A special focus is directed to the type and content of the implemented interventions. In turn, interventions that were designed to increase physical activity were contrasted with the programmes that strived to improve physical fitness as well as with the strategies to reduce sedentary time. The moderation of the effects by gender, with a specific focus on socially vulnerable groups of children (e.g. socially disadvantaged children, ethnic minorities) was also examined. The current contribution of sedentary behaviours and physical activity to the current obesity epidemic are poorly understood, the STOP project looked at comparing the effectiveness of interventions that aimed to increase energy expenditure by reducing sedentary behaviour with interventions that targeted physical activity or physical fitness, with a special attention directed towards evidence involving disadvantaged groups of children.