Table 1. Search strategy and study selection criteria.

Search Strategy
PubMed Search Strategy	((policy[Title/Abstract] OR policies[Title/Abstract] OR prevention[Title/Abstract] OR "primary prevention"[Mesh]) AND ("Child, Preschool"[Mesh] OR "Infant"[Mesh] OR childhood[Ti] OR childcare[Ti] OR early childhood[Ti] OR preschool[Ti]) AND (obesity[mh] OR obese[tiab] OR obesity[tiab] OR overweight[tiab] OR over-weight[tiab])) NOT (("Review"[Publication Type] OR "Meta-Analysis"[Publication Type] OR "Meeting Abstracts"[Publication Type] OR "research design"[Mesh]))
Limits	Full text; Publication date from 2001/01/01; Humans; English; Newborn: birth-1 month; Infant: birth-23 months; Infant: 1–23 months; Preschool Child: 2–5 years
Study Selection Criteria (PICOTS)
	Inclusion Criteria	Exclusion Criteria
Population	-Children under the age of 6 - Records/ separate analysis of children under the age of 6, if older children were also included -Otherwise healthy	-Populations of exclusively obese or overweight children -Children with a chronic illness, disability, congenital malformation or significant medical condition that could contribute to changes in body weight
Interventions, Policies or Practices	Any intervention, program or policy aimed at preventing early childhood obesity	-Interventions, programs or policies aimed at obesity treatment or promoting weight loss
Comparison	-Other intervention, programs or policy aimed at preventing early childhood obesity -Or usual care, within the same aged children and in a similar setting -Or an equivalent historical control group or policy period	-No relevant comparator group
Outcome	Change in a weight-based measure of growth or weight status such as weight, weight/weight percentiles, BMI / BMIz-score, or BMI categories (underweight, normal weight, overweight, obese) compared to a comparator group	-No weight-based outcome measure
Timing	-Interventions/programs lasting at least 6 months long or collecting a weight-based outcome measure 6 months after initiation -Policies since 2001	- Interventions/programs less than 6 months
Setting	-Individual (primary-care based) -Interpersonal (home-based, peers) -Community (childcare-based, community organizations) -Societal (policies, health information, social norms)	-Non-US settings or policies
Year Range	Publications from Jan 2001 to Feb 2018	-Publication prior to 2001
Studies estimating implementation costs, cost effectiveness analyses and policy studies were included provided that the assumptions and datasets included children under 6 years of age.