Ray 2020.

Study characteristics
Methods	Study design: cluster‐RCT Length of follow‐up from baseline: 5 months Unit of allocation: preschool centre Unit of analysis: child
Participants	Service type: centre‐based (preschools) Operation: not reported Country (region): Finland Country income classification: high Low‐SES sample: no Population description: municipalities that had a high number of preschools and had a large variety in educational and income levels among inhabitants were recruited. Inclusion criteria: municipalities that had a high number of preschools and had a large variety in educational and income levels among inhabitants as well as being located within a convenient distance from the Helsinki region were invited to participate. Exclusion criteria: municipalities that were already part of the comprehensive DAGIS survey in 2015–2016 were excluded. Number of services randomised: 32 (13 intervention, 19 control) Number of children randomised: 802 (361 intervention, 441 control) Characteristics Children Age: Intervention: 5.14 years (SD 1.04) Control: 5.24 years (1.06) Gender (% female): Intervention: 47.8% Control: 46% Ethnicity: not reported Parents Age (years): not reported Gender (% female): not reported Ethnicity: not reported Parent/family SES: Parental education Intervention: low: 35.4%; middle: 46.4%; high: 18.2% Control: low: 29.9%; middle: 43.6%; high: 26.5% Method of recruitment: altogether, 7 municipalities were invited to participate in the study, and an oral presentation on the study was offered. 5 municipalities had an oral presentation; 2 of these municipalities chose to participate. Researchers visited each preschool to inform early educator professionals about the project and their role in the project. The recruitment phase lasted 1–2 weeks, and families returned informed consents (or refusals to participate) to preschools in sealed envelopes. Missing data/dropout: between 10%‐18% of children were missing across diet outcomes. Reasons for dropout: not reported Characteristics of dropouts: not reported
Interventions	Programme name: The Increased Health and Wellbeing in Preschools (DAGIS) intervention Number of conditions: 1 intervention, 1 control Intervention duration: 23 weeks (5 months) Intervention setting: ECEC Intervention strategies: Health curriculum Children Education: educators delivered a programme around 5 healthy energy balance‐related behaviours (self‐regulation skills; physical activity; fruit and vegetables; screen time; and sugary foods and beverages). Ethos and environment Children Exposure: self‐regulation skills were promoted by brain breaks, which were a few minutes’ calming down and breathing sessions 3 times/d, led by early educators. ECEC staff Training: 2 x training (approximately 8 h total) Support: email support from researchers throughout the intervention. Service Environment: materials that were produced during the activity afternoons were expected to be displayed at the preschool, so that families could see each other’s work. Partnerships Families Workshops: children and families were invited to 5 activity afternoons delivered by preschools. The focus was set on the children’s energy balance‐related behaviours, and on how parents, by acting as role models and changing the availability and accessibility of the home environment can influence children's energy balance‐related behaviours. Resources: information letters, emails containing videos or articles, bingos related to energy balance‐related behaviour, and 2 fairy tales Intensity of intervention: 2 x training, totaling 8 h; 20‐25 weeks of child program; parent‐child workshops (frequency and duration not reported); parents received materials Intervention delivered by: research team, ECEC staff Modality: face‐to‐face, online, written Theoretical basis: Social Cognitive Theory, Theory of Planned Behaviour, and Self‐Determination Theory Description of control: wait‐list control
Outcomes	Outcomes relating to child dietary intake: Sugary everyday food and beverages intake, sugary treats intake, fruit and vegetable intake Number of participants analysed: Intervention baseline: 293‐299 Intervention follow‐up: 192‐200 Control baseline: 307‐323 Control follow‐up: 236‐238 Data collection measure: 51‐item FFQ (expanded from the original 47‐item survey) Data collector: parent Validity of measures used: validated Outcomes relating to child physical measures: not reported Outcome relating to child language and cognitive performance: Cognitive self‐regulation skills Number of participants analysed: Intervention baseline: 313 Intervention follow‐up: 256 Control baseline: 383 Control follow‐up: 324 Data collection measure: 5 items derived from the Child Social Behavior Questionnaire Data collector: not reported Validity of measures used: not reported Outcome relating to child social/emotional measures: emotional self‐regulation skills Number of participants analysed: Intervention baseline: 313 Intervention follow‐up: 256 Control baseline: 383 Control follow‐up: 324 Data collection measure: 5 items derived from the Child Social Behavior Questionnaire Data collector: not reported Validity of measures used: not reported Outcome relating to child quality of life: not reported Outcome relating to cost: not reported Outcome relating to adverse consequences: not reported
Notes	Funding source: financially supported by the Ministry of Education and Culture in Finland, The Ministry of Social Affairs and Health, The Academy of Finland (Grants: 285439, 287288, 288038, 315816), the Päivikki and Sakari Sohlberg Foundation, Signe and Ane Gyllenberg Foundation, and the Medicinska Föreningen Liv och Hälsa. Folkhälsan Research Center and University of Helsinki provided the infrastructure and the funding for PIs (N.S., M.E., E.R.) and key personnel (C.R., R.L.). Open access funding was provided by University of Helsinki. The funding bodies were not involved and did not interfere with the study at any stage.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation was made at the preschool manager‐level, separately for the 2 municipalities by an online randomisation program (https://www.randomlists.com/team‐generator).
Allocation concealment (selection bias)	Low risk	Preschools were divided into small and large preschools before randomisation. After the baseline measurements, preschools were informed whether they had been randomised into the intervention or control group.
Blinding of participants and personnel (performance bias) Diet outcomes	High risk	No blinding of participants and personnel to study allocation, and the outcome is likely to be influenced by lack of blinding
Blinding of participants and personnel (performance bias) Language and cognitive performance outcomes	Unclear risk	No blinding of participants and personnel to study allocation, and it is unclear whether lack of blinding would affect the outcome
Blinding of participants and personnel (performance bias) Social/emotional outcomes	Unclear risk	No blinding of participants and personnel to study allocation, and it is unclear whether lack of blinding would affect the outcome
Blinding of outcome assessment (detection bias) Diet outcomes	High risk	Parents completed the FFQ. Blinding of parents not reported, and the outcome measurement is likely to be influenced by lack of blinding
Blinding of outcome assessment (detection bias) Language and cognitive performance outcomes	High risk	Parents completed a questionnaire regarding children's cognitive self‐regulation skills. Blinding of parents not reported, and the outcome measurement is likely to be influenced by lack of blinding
Blinding of outcome assessment (detection bias) Social/emotional outcomes	High risk	Parents completed a questionnaire regarding children's emotional self‐regulation skills. Blinding of parents not reported, and the outcome measurement is likely to be influenced by lack of blinding
Incomplete outcome data (attrition bias) Diet outcomes	Unclear risk	Data were available for between 192‐200 (64%‐68%) children in the intervention group and between 236‐258 (74%‐80%) children in the control group. Reasons for loss to follow‐up are not provided. Study authors stated that "All analyses were based on the intention‐to‐treat principle so that all randomized participants were included in the analysis in their randomized intervention group." Risk of attrition bias is unclear.
Incomplete outcome data (attrition bias) Language and cognitive performance outcomes	Unclear risk	Data were available for 256 (82%) children in the intervention group and 324 (85%) children in the control group. Reasons for loss to follow‐up are not provided. Study authors stated that "All analyses were based on the intention‐to‐treat principle so that all randomized participants were included in the analysis in their randomized intervention group." Risk of attrition bias is unclear.
Incomplete outcome data (attrition bias) Social/emotional outcomes	Unclear risk	Data were available for 256 (82%) children in the intervention group and 324 (85%) children in the control group. Reasons for loss to follow‐up are not provided. Study authors stated that "All analyses were based on the intention‐to‐treat principle so that all randomized participants were included in the analysis in their randomized intervention group." Risk of attrition bias is unclear.
Selective reporting (reporting bias)	Unclear risk	The reported self‐regulation outcomes are not specified in either the trial registration or protocol paper.
Recruitment bias	Low risk	Full recruitment occurred before randomisation, according to the manuscript's PRISMA diagram.
Baseline imbalance	Unclear risk	Even though most characteristics were similar among groups, a higher percentage of children with high educational‐level parents were found in the control group (26%) compared to the intervention group (18%). Study authors report the comparison between the intervention and control groups at follow‐up adjusted for respective baseline outcome values.
Loss of clusters	Unclear risk	Not reported
Incorrect analysis	Low risk	Study authors stated that "The preschool unit was used as a random effect in order to adjust for variability between the preschools."
Contamination	Unclear risk	No evidence to make assessment.
Other bias	Unclear risk	Study authors stated that "Finally, the sample size might not have been sufficiently large to detect significant results. The power calculations were conducted based on means and standard deviations from the DAGIS cross‐sectional survey. Some dissimilarities exist between these 2 studies such as the number of preschools and municipalities and the proportion of low parental education level families participating, which might have led to an underpowered study." There is insufficient information to assess whether an important risk of bias exists. One study author is reported to be a board member of a relevant commercial organisation.