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. 2025 Aug 27;25(1):2952.
doi: 10.1186/s12889-025-24352-1.

Study protocol for a cluster-randomized controlled trial of a universal home-based, multi-component intervention to promote healthy weight development in children during infancy and toddlerhood in denmark: the bloom study

Camilla Thørring Bonnesen  1 , Mette Rasmussen  2 , Lene Kierkegaard  2 , Rikke Rothkegel Carlsson  2 , Marie Pil Jensen  2 , Thilde Risager Ubbesen  2 , Katrine Rich Madsen  2 , Lau Caspar Thygesen  2 , Rikke Fredenslund Krølner  2 , Louise Ayoe Sparvath Brautsch  2 , Johanne Aviaja Rosing  3 , Line Planck Kongstad  4 , Mette Skovgaard Væver  2   5 , Ida Egmose  5 , Trine Pagh Pedersen  2
Affiliations

Study protocol for a cluster-randomized controlled trial of a universal home-based, multi-component intervention to promote healthy weight development in children during infancy and toddlerhood in denmark: the bloom study

Camilla Thørring Bonnesen et al. BMC Public Health. .

Abstract

Background: Child overweight and obesity are major public health challenges associated with poor physical, psychological, and social health through life. This protocol describes the study design for the Bloom Study, an evaluation of a theory- and evidence-based intervention addressing infancy and toddlerhood (age 0-3 years) to promote healthy weight development among children in Denmark.

Methods: The Bloom intervention is evaluated through an open-label, two-arm, cluster-randomized wait-list control trial, with 22 municipalities randomly allocated to 11 intervention and 11 control municipalities. All first-time families within one year are invited (approximately 3200 families). The intervention was developed using the Intervention Mapping protocol and a thorough co-creation process. It is delivered through the Danish community health nursing system and includes four main components: (1) Home visits, (2) Proactive telephone consultations, (3) Parent groups for both parents, and (4) A video library. The intervention begins during pregnancy (between weeks 22-24) and continues until the child is 30 months. The primary outcome measure is the BMI z-score at 36 months of age. Secondary outcomes relate to the key determinants of child weight development targeted by the Bloom intervention, including food and meals, sleep, movement and motor skills, screen use, and family sense of security. A comprehensive mixed methods process evaluation and a health economic evaluation will also be conducted.

Discussion: The protocol outlines the evaluation of a theory- and evidence-based intervention aimed at promoting healthy weight development in infants and toddlers in Denmark. Overall, the study has the potential to inform future health promotion initiatives at the municipal level, supporting healthy weight development during early childhood.

Trial registration: ClinicalTrials.gov ID: NCT06705400. Registered November 21, 2024.

Keywords: Community health nurses; Effect evaluation; Health economic evaluation; Healthy weight development; Infants; Overweight; Process evaluation; Randomized controlled trial; Study design; Toddlers.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: Ethical approval for the Bloom Study was obtained from the Scientific Ethics Committee of the Capital Region (reference number H-24032126). Any subsequent protocol amendments will be submitted to the Scientific Ethics Committee of the Capital Region for evaluation and will also be updated in the registration at www.clinicaltrials.gov (NCT06705400). The Bloom Study will be conducted in accordance with the Danish Code of Conduct for Research Integrity and the ethical principles in the current version of the Declaration of Helsinki. All custody holders of children participating in the study will provide written informed consent for their child’s and for their own participation in the study. We place special emphasis on avoiding weight-related stigmatization and negative focus on body weight. For example, all communication will carefully be prepared to ensure that children and families are not stigmatized. Additionally, the training course for community health nurses includes education on diversity competencies. Staff conducting data collection will be trained to ensure that families always feel comfortable and secure, and to know how to handle any issues that arise during measurement visits. Finally, it is crucial that the intervention at no point jeopardizes the families’ acceptance and trust in the community health nurse system. Implementation of the intervention will be based on the community health nurse’s evaluation of the family’s most urgent needs. If for example a family is experiencing severe social challenges, these will always be priority of the guidance and support provided by the community health nurse. A close continuous dialogue with community health nurses will support this ethical awareness. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests. Data management and data security: All collected data will be processed and stored in accordance with the Data Protection Act and comply with the GDPR (EU) 2016/679. The data collections are registered and approved at the University of Southern Denmark (reference number 12.301). Questionnaire data will be collected via a secure online survey database (REDCap) hosted at OPEN Storage, OPEN, Open Patient Data Explorative Network, Odense University Hospital, Region of Southern Denmark. All quantitative data applied in the study will be stored at Statistics Denmark, where analyses will be conducted. Publication and dissemination: The trial’s pre-registered primary and secondary outcomes will be reported in accordance with the CONSORT guidelines and published in peer-reviewed journals. Additionally, the results will be presented at conferences to disseminate findings to the scientific community and relevant stakeholders. Lay summaries will also be made available on the project’s website for participating municipalities, local stakeholders, and parents. The authors and contributors to publications related to the project will be determined in line with the recommendations of the International Committee of Medical Journal Editors (ICJME). Study organization: The Bloom Study is anchored at the National Institute of Public Health, University of Southern Denmark. The study is led by a management group consisting of the the principal investigator (PI) (CTB), co-PI (MR), KRM, and TPP, and is carried out by the Bloom Study project group. The study is structured into three work packages (WPs): WP1 focuses on the effectiveness evaluation (led by MR), WP2 on the process evaluation (led by CTB), and WP3 on the health economic evaluation (led by LPK). Additionally, the study is supported and overseen by a Steering Committee, which monitors trial progress, advises on scientific credibility, reviews accumulated trial data, and makes recommendations on whether the trial should continue or if modifications to the protocol are necessary. The Steering Committee includes the Bloom Study management and project groups, along with senior researchers from the National Institute of Public Health, University of Southern Denmark; DaCHE - Danish Centre for Health Economics, University of Southern Denmark; Centre of Excellence in Early Intervention and Family Studies, Department of Psychology, Copenhagen University, Local Government Denmark, and a representative from the Danish National Organization of Leading Community Health Nurses. The study also has an International Advisory Board, consisting of prominent national and international scientists in the fields of child overweight and obesity, obesity prevention, community-based intervention research, nutrition epidemiology, and social epidemiology. In the spring 2025, a Sounding Board will be convened to discuss the study’s progress, dissemination, and potential strategies for scaling up the intervention if deemed appropriate. The project does not have an External Data Monitoring Committee due to the minimal risks associated with the intervention.

Figures

Fig. 1
Fig. 1
Flow diagram of municipalities and participants in the Bloom Study
Fig. 2
Fig. 2
Program theory of the Bloom Study
Fig. 3
Fig. 3
Timeline of delivery of the Bloom intervention components
See this image and copyright information in PMC

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