The increase of the prevalence of the obesity in childhood puts in reason some factors of the environment and the way of life of the child that encourage the hold of weight at these topics of as much more that if they are exposed genetically. A prospective survey has been done close to 3148 school boy aged of 6 to 10 years and who were schooled in the gouvernorat of Ariana showed that the prevalence of the obesity is around 3.7%. A survey case/witness has been achieved in a second time on the way of life of the group of the obese matched to a group of children no obese. An intended questionnaire to parents of children of these 2 groups permitted to collect some informations concerning the weight and the present size of parents, habits of life of their children. The weight to the birth has been searched for in the school medical file or from the notebook of health of the child. The obesity of parents is one factor of risk of the child obesity. The short length of sleep (< 8 hours), the erosion between meals especially in the evening after the dinner, the daily consumption of sugary foods and sparkling drinks is the important risk factors exposing to the infantile obesity this group of age. These behaviours can be corrected by a strategy of prevention and nutritional education.