The Cally App A health app as a supporting medium in a school-based nutrition and lifestyle intervention (Eddy Young 2) for 8-to 11-year-olds

Background Childhood obesity is an alarming problem that makes it essential to invest effectively in its prevention. The Eddy Young 2 project was a prevention study that used school-based nutrition and physical activity interventions. Additionally, a health app was developed. Methodology During the school year 2017/18, 52 children (ages 8-11) participated in the "Eddy" intervention once a week. In addition, the children were introduced to the "Cally App" in which they were asked to provide a balanced diet to a virtual pet. The Usage of the app remained voluntarily. Results The duration of app use in the school year 2017/18 averaged 10.34 days of play (arithmetic mean). The median was 4 days. Conclusion During the first lessons of the intervention, the children showed great enthusiasm for the app; however, contrary to our expectations, it was used very little over the course of the entire school year. In order to be able to use apps for children in the longer term, consideration should be given to working with a reward system or gamification elements.