One of the main aims of the European Childhood Obesity Group (ECOG) is to assist healthcare workers in delivering evidence-based assessment and treatment of childhood obesity. Every year the ECOG Congress includes working groups whose objective is to highlight concerns faced by clinicians and practitioners who work in the field of pediatric obesity. This year, a working group was devoted to the assessment of physical activity and physical fitness in this population. The present commentary attempts to summarize the main themes identified by practitioners during these workshops in order to provide the basic and essential first steps required to address physical activity and fitness in children with obesity.