How can professionals in Youth Healthcare help prevent obesity in children from birth? That is the key question in this study. It has been established that the early infancy period is a key life stage for the development of obesity in later life. Once a child has become obese, it is difficult for them to get back to a healthy weight. This study examined whether a training programme for paediatricians and paediatric nurses had an impact on Youth Healthcare practice and the weight development of children between the ages of zero and two. The result turned out to be an improvement among the group of paediatricians and paediatric nurses who had undergone the training programme when compared to a group who had not undergone training. They were more aware of the importance of preventing obesity in the first year of life, and found it easier to discuss obesity (or the risk of obesity) with the parent. No significant change was identified in the weight development of the children.