In this episode, we talk with Dr. Mark Tremblay. Dr. Tremblay is a Professor in the Department of Pediatrics at University of Ottawa, in Canada. He has devoted most of his career to study how physical activity affects different aspects of health in children, childhood obesity and the factors that can increase or reduce PA in this population. In this episode we cover many topics. We first talk about the trends of PA, overweight and obesity in children. We discuss the difference between lack of physical activity and sedentary behaviour and the price that we can pay for the latter. We also discuss the association between screen time and PA, the use of active-video games to promote PA, the importance of exercising in natural environments and what can we do to ensure that our children exercise enough. The conversation is truly fascinating. You can follow Dr. Tremblay's research at https://www.haloresearch.ca/dr-mark-tremblay/.