In this thesis I will discuss the problem of obesity in preschool children. All over the world the problem of obesity is growing, not just in adults, but also young children. In my thesis I will define obesity, list its causes, and explain the best ways to prevent it as well as help children who are already obese. The goal of this thesis is to familiarize the reader with the problem of obesity, to explain the importance of this problem which affects more and more children and adolescents because of our fast paced way of life, and to emphasize the importance of a healthy and balanced diet as well as an active lifestyle. Parents, alongside with childcare and healthcare personel, play a key role in the process of teaching children a healthy lifestyle, and they should a ll work together to improve the health of the child. In this thesis interviews with parents, childcare and healthcare workers were used, and they h ave shown that a good and collaborative relationship between these three factors is extremely important in a childs life as it grows up. A childcare worker should provide support to parents with their open and positive attitude, and healthcare personel should share their knowledge and expert oppinions with them. However, the most important factor in leading a healthy lifestyle with a balanced diet and plenty of physical activity have to be the parents themselves, as they are the ones who children observe everyday and copy their habits. It is important to note that mothers are responsible for their childrens health from the very beginning,as they create their own menu and activity habits, in their pregnancy and in the postpartum period. A busy lifestyle, along with fast food and lack of physical activity, as well as a general negligence toward our body and mind have all led to a staggering percentage of obese preschool children.