[Childhood obesity: a new vision].

There is considerable evidence that, in an obesogenic environment, constitutional susceptibility to fat gain is necessary for a given child to become obese. Only children highly sensitive to abundant palatable food and with conditions favouring little physical activity are at risk of obesity. A high-risk environment has no effect on non predisposed children. An obesogenic environment is therefore a trigger but not the primary cause of obesity: it simply enables phenotypic expression of a genetic predisposition. As most children are not constitutionally predisposed to obesity, prevention strategies should focus on children at risk. This is supported by the disappointing results of most collective interventions, particularly at school. In addition, broad-reaching preventive campaigns may increase discrimination towards obese children and induce eating behaviour disorders in non predisposed children. Children at risk of becoming obese are those who have adiposity rebound before 6 years of age. These at-risk children must be detected early and offered personalized interventions aimed at preventing further fat gain. In the future, the improvement of obesity pathophysiology knowledge will probably allow the development of more promising preventive approaches.