In schools and in society it is argued about the importance of living a healthy life. The discus-sions are often focusing on different kinds of food. In this paper the focus is on students’ knowledge about the human body and how this is related to their thoughts about living a healthy life. 88 students in 9:th grade, in one Swedish school, were involved in the study. The study contains drawings and written questions, both open and multiple- choice, and interviews with students and teachers. We report that it is possible for the pupils to transfer knowledge from one context to another, (sandwich and painkiller) concerning pathways in the digestive system. But it is harder for them to connect different organ systems in their explanations, e.g. water's path through the body. More than half of the interviewed pupils believed that there is nutrition in water, but most of them were unable to specify what this nutrition consists of. It was also found that a few students believed that the body stores nutrition and energy when they skip a meal.