BackgroundThis study assessed initial feasibility and preliminary efficacy of providing children a free summer day camp and a parent intervention to improve self-regulation and mitigate accelerated summer BMI gain.MethodsThis pilot 2x2 factorial randomized control trial used a mixed methods design to evaluate providing children a free summer day camp (SCV), a parent intervention (PI), and the combination of these two strategies (SCV + PI) to mitigate accelerated summer body mass index (BMI) gain. Feasibility (i.e., recruitment capability, retention, compliance, treatment fidelity, acceptability) was examined using means, standard deviations, and percentages for relevant variables. Changes in BMI were estimated using intent-to-treat and post-hoc dose response analyses via multilevel mixed effects regressions.ResultsA total of 89 families participated, with 24 participants randomized to the PI group, 21 randomized to the SCV group, 23 randomized to the SCV + PI group, and 21 randomized to the control. Parents and children found the summer program acceptable but attendance at the summer program and engagement in the PI were low due to COVID-19 and lack of transportation. Intent-to-treat analyses showed no statistically significant difference between groups in summer BMI gain. Post-hoc dose response analyses showed that for each day (0 to 29) of summer programming children attended they gained - 0.009 (95CI= -0.018, -0.001) less in BMI z-score.ConclusionsEngagement in both the SCV and PI was not ideal and was likely due to COVID-19 and lack of transportation. Providing children with structured summer programming to mitigate accelerated summer BMI gain may be an effective strategy. Thus, a larger trial may be warranted, but more work is needed to ensure children attend the programming.Trial registration: The trial reported herein was prospectively registered at clinicaltrials.gov. Trial #:NCT04608188.