Nyberg 2015.

Study characteristics
Methods	Study design: cluster‐RCT Intervention period: 6 months Follow‐up period (post‐intervention): 6 months Differences in baseline characteristics: reported Reliable outcomes: reported Protection against contamination: NR Unit of allocation: class Unit of analysis: individual accounting for cluster
Participants	N (control baseline) = 114 N (control follow‐up) = 112 N (intervention baseline) = 129 N (intervention follow‐up) = 127 Setting (and number by study group): 8 schools with 14 preschool classes (14 classes in each group) Recruitment: the schools included were within the school physician’s administrational area; parents were informed verbally about the project at regular school meetings and were also informed through a letter written by the research team and the school physician Geographic region: a municipality in Stockholm County, Sweden Percentage of eligible population enrolled: 53% schools, 40% participants Mean age: intervention: 6.2 ± 0.3; control: 6.2 ± 0.3 Sex: intervention: 47% female; control: 51% female
Interventions	To evaluate the effectiveness of the 6‐month 'Healthy school start' programme on children’s PA and healthy eating habits and on the prevention of overweight and obesity in 6‐year‐old children attending preschool class. 3 components to the intervention: health information for parents (a brochure was developed and sent home to parents with the aim to increase parental knowledge on how to promote children’s dietary and PA habits, containing facts and advice for parents within 7 areas: parental feeding practices; healthy food and family meal times; PA sweets, snacks, ice‐cream and sodas; fruit and vegetables; physical inactivity, screen time, and commercials; sleep MI with parents (parents in the intervention group were offered 2 sessions during the intervention period with a trained external provider) Teacher‐led classroom activities with children with ten 30‐min teacher‐led sessions (a teacher’s manual and a workbook for children were developed to facilitate the classroom activities. The activities were related to the different areas in the brochure, for example discussing the importance of eating fruit and vegetables and thereafter trying a new fruit or vegetable). Teachers were trained for the classroom activities by the research team for 2 h Control classes were offered the whole programme directly after the 6‐month follow‐up measurements Diet and PA combination intervention vs control
Outcomes	Outcome measures Primary outcome: PA Secondary outcomes: dietary intake, parental self‐efficacy, BMI SDs, waist circumference, prevalence of underweight, normal weight, overweight and obesity Process evaluation: reported: fidelity, compliance
Implementation‐related factors	Theoretical basis: SCT Resources for intervention implementation: reported Who delivered the intervention: reported PROGRESS categories assessed at baseline: child: gender; parent: education; race/ethnicity PROGRESS categories analysed at outcome: NR (for anthropometric) Outcomes relating to harms/unintended effects: reported (change prevalence of underweight) Intervention included strategies to address diversity or disadvantage: NR Economic evaluation: NR
Notes	ISRCTN32750699 Funding: ES and LSE received funding for this study from the Public Health Fund, Stockholm County Council. GN received funding from the Signhild Engkvist Foundation, the Martin Rind Foundation and the Lars Hierta Memorial Foundation.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomisation, no further details
Allocation concealment (selection bias)	Unclear risk	Randomly assigned by the research assistant
Blinding (performance bias and detection bias) All outcomes	Unclear risk	NR
Incomplete outcome data (attrition bias) All outcomes	Low risk	Very few dropouts (3%); ITT done
Selective reporting (reporting bias)	High risk	Protocol seen; only reports effect by gender for main outcome (PA); only reports BMI in text (whereas other outcomes reported in tables) and only reports data immediately post‐intervention not follow‐up. Does not report waist circumference although measured. Economic variables NR (even though mentioned in the protocol that costs of the intervention will be calculated by an economist)
Other bias	Low risk	No additional threats to validity
Other bias‐ timing of recruitment of clusters	Low risk	Figure shows recruitment happened prior to randomisation