Attained body mass index among children attending outdoor or conventional kindergartens

BACKGROUND Studies have shown that outdoor activities are inversely associated with adiposity, but little is known about outdoor kindergartens as a potential intervention for healthy weight development. METHODS We included 1544 children from outdoor kindergartens and 1640 from conventional kindergartens. Anthropometry was measured by school health nurses when the children were 6 to 8 years old. The first available measure of attained body mass index z-score (BMIz) after school entrance was included as the primary outcome. Risk of attaining overweight (including obesity) was included as a secondary outcome. Register-based information was available on potential confounding factors. Regression models were constructed to examine differences in study outcomes between children attending outdoor or conventional kindergartens. RESULTS Our basic models, with information on outcome, kindergarten type and birth weight, showed a borderline statistically significantly lower attained BMIz (−0.07 [95% CI: −0.14, 0.00], P=0.060) and a lower risk of overweight (adjusted risk ratio: 0.83 [95% CI: 0.72, 0.97], P=0.016) among children attending outdoor kindergartens compared to conventional kindergartens. When adjusting for sociodemographic factors and parental BMI, there was no evidence of differences in attained BMIz (P=0.153) or overweight (P=0.967). CONCLUSION Our results do not support outdoor kindergartens as an intervention for healthy weight development. What is already known about this subject? What are the new findings in your manuscript? How might your results change the direction of research or the focus of clinical practice? Article Summary This study examined whether children in outdoor kindergartens had a lower risk of overweight after school entrance compared to children in conventional kindergartens. ### Competing Interest Statement Sofus C. Larsen and Nanna J. Olsen have no conflicts of interest relevant to this article to disclose. Jeanett F. Rohde have had two children enrolled in an outdoor kindergarten. Jane N. Ostergaard have had three children enrolled in a conventional kindergarten. Berit L. Heitmann have had two children enrolled in an outdoor kindergarten. Ina O. Specht have had one child enrolled in an outdoor kindergarten and one child enrolled in a conventional kindergarten ### Funding Statement The study was funded by grants from Den A P Mollerske Stottefond (grand no.: 12408), Helsefonden (grand no.: 19-B-0079), Rosalie Petersens Fond (grand no.: 020432-0001), Beckett-Fonden (grand no.: 20-2-6761) and Aase og Ejnar Danielsens Fond (grand no.: 21.5.2019). The Parker Institute is supported by a core grant from the Oak Foundation (grant agreement number OCAY-18-774-OFIL). Dr. Ostergaard is employed at Steno Diabetes Center Aarhus, a public hospital and research institution situated in Central Denmark Region, which is partly funded by a grant from the Novo Nordisk Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Permission from the two municipalities to send information to Statistics Denmark was granted. Ethical permission was decided not to be relevant by the Ethical Committee of the Capital Region of Denmark (journal nr.: H-19053587). Permission from the Capital Region Data Agency and the Danish Patient Safety Authority was granted (Journal nr.: P-2020-54 and 31-1521-8, respectively). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Data is stored on a secured server at Statistics Denmark (https://www.dst.dk/en/). Due to Danish legislation, the individual‐level data used in the present study cannot be made available.