Child and adolescent obesity is definitely a pathology the understanding of which has faced dramatic changes in recent years thanks to the identification of the genetic background of some cases and an amazing increase in the knowledge of its biological background. The adipose tissue is an endocrine organ in permanent communication with other ones, including the appetite regulation centres of the brain and the neuroendocrine system of the digestive tract. A precise analysis of the trajectory of weight gain and its associated manifestations such as abnormal physical or developmental features and complications is mandatory while facing a child or adolescent with obesity. A close cooperation with reference centres for childhood obesity and nutrigenomics research units leading to the diagnosis of genetic forms, likely to be underdiagnosed, may allow the use of targeted and efficient drug treatment. A recent double-blind study has shown that a Glucagon like peptide 1 (GLP1) analogue, a key contributor of appetite regulation from intestinal origin, has a major beneficial impact on adolescents with obesity of polygenic origin. Further studies are still required to ensure the long-term effect and the lack of side effects of such a treatment. However, such results already challenge the indication of bariatric surgery. While prevention still must be a priority, many other molecules and therapeutic approaches are underway for the most frequent metabolic and chronic childhood disorder.