2.2 The Population of Study

All seventh-grade students (N=80) who were obese or overweight and attending in the high-school classes in intervention and control schools were invited to complete the questionnaires. Incentives for the intervention group (n= 40 obese or overweight students) who participated in briefing classes were described (sports shirt). The control group (n= 40 obese or overweight students) from the selected high schools completed baseline questionnaire. Each student was provided written informed consent before data collection. The students were informed that all the obtained data were used without personal identifiers and were therefore confidential.