Table 1

Description of the intervention components implemented in the DECIDE-Children study

Intervention componentsDescriptions of the content, frequency and durationPerson responsible
1.Student-focused activities
Health education activities for students (1) Frequency and duration
 A total of ten activities (each lasting 40 min) will be provided once every two to 3 weeks (six activities will be arranged in the first semester, and four will be arranged in the second semester).
 (2) Different kinds of activities
 The ten activities will include seven health education lectures and three theme class meetings. The focus of the health education lectures will be on information diffusion, while the focus of theme class meetings will be on consolidation of the key messages learnt in health education lectures through interactive and interesting group work (eg, ‘Let me guess’).
 (3) Content
 1) Information diffusion
 Key messages will include the benefits of healthy weight, measurements and assessments of weight, and methods of achieving a healthy weight (not eating excessively; not drinking sugar-sweetened beverage; eating less high-energy food; less sedentary behaviours; performing more physical activity). Health education books and ‘nutrition evaluation turnplate for Chinese primary and middle school students’ will be delivered to students. Health education messages will also be spread through posters on campus or in the classroom.
 2) Promotion for translating knowledge into action
 ‘Small hand in big hand’ homework (eg, ‘challenge of 3 days away from screen’) will be arranged at the end of each health education activity.
 3) Feedback and encouragement for BMI and behaviour change
 Feedback of regular monitoring results of students’ BMIs and behaviours will be provided in each health education activity. The students with good performance will be encouraged.
The trained class teachers
Reinforcement of students’ physical activity within school1) Students will be instructed by physical education teachers to perform physical activities with moderate-to-vigorous intensity at school for at least 1 hour per school day (including physical education classes, class-break exercise, extracurricular activities). The aim of this component will be to improve the adherence to the Chinese national requirement for ‘One-Hour Physical Activity On Campus Every School Day’. If a school has met this requirement, no extra physical activities will be added at the school; otherwise, extra physical activities (ie, physical education classes, exercises during breaks in class or extracurricular activities) will be added to the school schedule. The monitoring of the implementation of these extra physical activities will be continuous within the intervention period for the intervention group;
2) Physical education teachers will be advised to teach students at least one sports game during each extracurricular activity.
The trained physical education teachers
Regular monitoring of students’ weight and height1) Monthly monitoring
Students’ weight and height will be monitored monthly, and the data will then be input into the computer management system in a timely manner and shown in the smartphone app (described below);
2) Weekly monitoring
Students’ weight will be monitored weekly by the students themselves in the classroom.
The trained school doctors/healthcare teachers with the assistance of the trained project staff (for monthly monitoring);
The trained project staff (for data input of monthly monitoring)
Students (for weekly monitoring)
2.Activities towards parents (providing a supportive family environment)
Health education activities for parents1) Frequency and duration
 At least one activity (lasting for approximately 40–60 min) will be held at the beginning of each semester. One more activity will be held in the middle of the first semester. Another activity will also be held in the middle of the second semester if necessary (for example, if the fidelity of the data is unsatisfactory).
2) Contents
  •  For the first activity

 Key messages will be similar to those for the health education activities for students (described earlier). Parents will also be taught to use the smartphone app.
  •  For other activities

 Project staff will provide feedback about students’ weight status and behaviours to parents. Face-to-face group discussions will be established between the project staff and parents.
The trained project staff
Reinforcement of students’ physical activity outside school1) Parents will be instructed to supervise and encourage students to perform physical activities outside of school for 30 min per weekday and 1 hour per weekend day;
2) Recommendations for physical activity outside of school will be provided through the smartphone app once every 2 months;
3) Students will be encouraged to participate in sports games outside of school that will be taught by their physical education teachers during extracurricular activities.
Students’ parents
3.Activities towards schools (providing a supportive school environment)
School policies related to obesity preventionThe following school policies will be suggested:
1) ‘Not selling’:
Not selling unhealthy snacks* or sugar-sweetened beverages within school;
2) ‘Not eating’:
Telling students not to eat unhealthy snacks or drink sugar-sweetened beverages at school;
3) ‘Not buying’:
Students being educated by class teachers not to buy unhealthy snacks or sugar-sweetened beverages around school.
The trained school principal;
The trained class teachers
Health education activities for school teachers1) Frequency and duration
The activity will be held once (lasting for approximately 40 min) in the first month of the intervention. School teachers participating in this programme at each school (school principal, class teachers, school doctors/healthcare teachers and physical education teachers) will be required to attend the activity.
2) Content
Key messages will be similar to those for the health education activities for students (described earlier). School teachers will also be taught to use the smartphone app.
The trained project staff
4.A smartphone app assisted in implementation of the intervention
The smartphone app (‘Eat Wisely, Move Happily’)1) Information diffusion (the BCT used: providing information on consequences of behaviours)
The smartphone app will provide information to parents, class teachers and project staff in accordance with the health education activities.
2) Behaviour monitoring (the BCT used: prompting the self-monitoring of behaviours)
Parents together with their children will be asked to record the diet and physical activity behaviours of students in the app weekly, and then they will receive individualised feedback related to these behaviours (described in table 2).
3) Weight management (the BCT used: prompting self-monitoring)
According to the monthly monitoring of students’ weight and height (described earlier), parents, school teachers and project staff will view the recent weight status (categorised according to the BMI percentile criteria24), changes compared with previous records of the students and the individualised feedback related to weight management (described in table 2).
4) Assessment and feedback (the BCT used: providing feedback on performance)
The smartphone app will also provide a synthetic and individualised assessment that will combine changes in the behaviours and weight status of the students. The four kinds of feedback are shown in table 2.
The smartphone app (installed by parents, school teachers and project staff) and the computer management system (utilised by project staff)
  • *‘Healthy snacks’ refer to dairy products, fresh vegetables or fruits and natural unprocessed nuts that are eaten at times other than at main meals. ‘Unhealthy snacks’ refer to snacks other than the three kinds of healthy snacks.

  • BCT, behaviour change technique; BMI, body mass index; DECIDE, Diet, ExerCIse and CarDiovascular hEalth.