The Genyal Project for the Prevention of Childhood Obesity is a longitudinal, prospective study lasting fi ve years that began in January 2017 under the auspices of the Dirección General de Centros de Educación Infantil, Primaria y Especial (General Directorate for Infant, Primary and Special Schools). It involves six schools in different parts of the Madrid Region (north, central and south), and a total of 221 children in their fi rst and second years of primary education. The main goal of the project is to design and validate a predictive model able to identify children likely to benefi t most from actions aimed at reducing the risk of obesity and its complications, taking into account the genetic and environmental factors of infl uence at this time of life. All the children have been studied from a nutrigenetic point of view (measuring, anthropometric, dietetic, and health and social variables, and taking into account single nucleotide polymorphisms associated with childhood obesity), and all will undergo annual checks and assessments until the end of the study period. The participating schools were assigned to either the treatment or control arm, and those in the former received material designed by nutritionists for delivery to the children, their teachers, and their parents. Information is also provided to teachers and parents via talks, and to the children via workshops. The latter try to teach healthy food habits through play. Many interesting results have already been collected regarding the nutritional status of the children, and the association of this with their environment and genetic characteristics. Plans are being drawn up to increase the sample size and, according to the results obtained, develop new interventions that involve further agents of change in children’s lives (the characteristics of the children themselves, the communities in which they live, wider society, governmental bodies, etc.) to combat this problem and its consequences.