The epidemic of obesity concerns 17% of Swiss children. This chronic condition leads to many complications that can already be seen during early childhood. It is therefore of primordial importance to detect them as soon as possible, as they are, in turn, followed with high morbidity and mortality in adults. We could demonstrate in our cohort study that almost 90% of the overweight and obese children were suffering of at least one medical complication, with already 30% of them presenting at least one cardiovascular risk factor. Other conditions shouldn't be underestimated as they impact the quality of life, the mental health as well as the treatment success rate. Through our research, we assessed the prevalence of the majority of those complications and studied the influence of physical activity on cardiovascular and metabolic health of our patients, as it is also a key point in the obesity treatment strategy.