Siegrist 2018.

Study characteristics
Methods	Study design: cluster‐RCT
Participants	School inclusion criteria: all secondary schools in the greater district of a city in Southern Germany that were willing to take part over 4 years and to be randomised to an intervention school with a lifestyle intervention programme or a control school School exclusion criteria: outside of the study area (distance > 30 km) Student inclusion criteria: Grade 5, parental consent Student exclusion criteria: — Setting: school Age group: children Gender distribution: females and males Country where trial was performed: Germany
Interventions	Intervention: school prevention programme aimed at increasing PA inside and outside of school through regular exercise in sports lessons and additional PA in school (active breaks during lessons, active school breaks). Weekly lifestyle lessons were taught by school teachers and were reinforced by worksheets, homework, and practical instructions. The programme also intended to improve eating patterns and other health behaviours (reduction in media use and inactivity). Teachers took part in 4 to 6 annual training sessions. Parents received regular newsletters and were invited to a parental training programme 2 to 3 times per year, which included coaching parents to lead a more active lifestyle and providing nutritional counselling regarding family dinners.  Comparator: control schools were asked to continue their usual activities Duration of intervention: 18 months Duration of follow‐up: 18 months Number of schools: 15 Theoretical framework: social cognitive theory
Outcomes	BMI
Study registration	NCT00988754 (retrospectively registered)
Publication details	Language of publication: English Funding: non‐commercial funding (governmental organisation) Publication status: peer‐reviewed journal
Stated aim for study	"we implemented a comprehensive cluster‐randomised school‐ and family based lifestyle‐intervention trial in secondary schools with aim to improve PA, physical fitness and cardio metabolic risk factors in children"
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote from publication: "randomisation of schools was conducted by sealed envelopes (1:1) in 8 intervention and 7 control schools"
Allocation concealment (selection bias)	Low risk	Quote from publication: "randomisation of schools was conducted by sealed envelopes (1:1) in 8 intervention and 7 control schools"
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote from publication: "a limitation of our study is that the main coordinator of the study was not blinded to the group assignments of the schools"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote from publication: "we tried to eliminate this bias by blinding medical examiners who were not aware of the group allocation of the participating children"
Incomplete outcome data (attrition bias) Anthropometrics, Fitness	Low risk	Comment: most loss to follow‐up due to moving schools
Selective reporting (reporting bias)	High risk	Comment: quality of life and anthropometry not reported
Cluster RCT ‐ Recruitment bias	High risk	Comment: randomisation at school level before enrolment of students
Cluster RCT ‐ Baseline imbalance	Low risk	Comment: models adjusted for key baseline differences [author communication]
Cluster RCT ‐ Loss of clusters	Low risk	Comment: no clusters lost
Cluster RCT ‐ Incorrect analysis	Low risk	Quote from publication: "data were aggregated per cluster to account for the cluster‐randomised design in the statistical analysis"