<p>Healthy physical activity and well-balanced diet are means of maintaining and promoting health. The presented Project Day involving pupils of the 1<sup>st</sup> level of elementary school in Senice na Hané focuses on well-balanced diet and health enhancing physical activity in terms of the current educational reality. These two phenomena are inseparable. One is associated with the other, they complement each other. They are the two crucial aspects of a healthy lifestyle of each individual. Without a balanced and appropriate diet, physical activity of pupils is useless. The main objective of the Project Day called “A sound mind in a sound body” was to, in a playful way, familiarize the pupils with basic information concerning diet and health benefits of physical activity. The aim of the initial part was to motivate the pupils for activity at various activity points. This part included a brief introduction with information about division into groups, duration at various activity points (length of activity at a specific activity point and length of transfers between activity points). The pupils were shown a short sketch, which symbolised a “clash” between the importance of diet and physical activity for humans. In their groups, the pupils were supposed to answer the principal motivation question: What is healthier for a human? Healthy food or sport? The following main part of the Project Day held on 2 December 2014 was attended by 69 pupils and was organized as group work at various thematic activity points. Each group visited all activity points. Activity point 1 was called “Agile duck-bill”, where the pupils tried out and learned about various preconditions for certain types of physical activity. The key competences involved communication, personal, social, and learning. The second activity point was called “Forest supermarket” and focused on the issue of a sedentary lifestyle. The key competences involved communication, personal, social, learning, problem solving, professional, and civic. The following activity point called “Juicy blueberry” focused on determining the importance of fruit and vegetables in terms of a balanced diet. The key competences involved communication, personal, social, learning, professional, and civic. The fourth activity point was called “Oversalted chip”, where the pupils were supposed to understand the negative health consequences of consuming fast food. The key competences involved personal, social, learning, and professional. The last activity point called “Great pyramid” invited the pupils to place various types of food into a pyramid. The key competences involved learning, problem solving, communication, professional, social and personal, professional, civic.</p><p>During a break the pupils completed worksheets, and in groups though about the principal motivation question. The project was completed by a final assembly of all participants, and by joint reflection in classes.</p><p>The present paper is not a traditional field-based research study. This is a project day, which followed a previous questionnaire survey on pupils’ healthy lifestyle and anthropometric measurement of pupils under the following project: The epidemic of obesity – a common problem: knowledge transfer, education, prevention under Reg. No. PL.3.22/2.3.00/11.02576.</p>