This research studies a problem of too little physical activity of children (as well as adults) and excessive growth of body weight, which has negative consequences on health. Researching the problem will bring out some suggestions of how to change the habits of children as well as bring changes wider to environment.   The research will be carried out on stratified sample of children of both genders, in the period of four years. With such longitudinal approach we are going to see more clearly the changes in the development of the children.   We will try to determine if there are any factors, which prevent children to be more physically active and to eat healthier. With questioners, for children and their parents, we will try to find out what are the characteristics of physical activities in or out of school. Our goal is to determine what kinds of opportunities have children in the surrounding where they live and at their schools. We are going to measure physical activity with hart rate monitors and calorie monitors. Children will be measured during the school days and weekends. Each child is going to carry calorie monitor around his arm, elastic band around his chest and heart rate monitor on the wrist for four days in a row, including Saturday and Sunday. The complete collection will include data of body development, motor characteristics and measurement of oxygen expenditure with telemetric measurement devices.   One of the questioners is going to establish, the nutritional habits of children. With it we will gather iformation that will allow us to investigate school lunches and types of snacks that are available in schools. Parallel to all these measurements we are going to determine the quality of nutrition, level of activity and body fat are on recommended level for healthy children and if there are any possibilities of improving nutritional and physical habits of the children.