Summary Background COVID‐19 school closures pose a threat to children's wellbeing, but no COVID‐19‐related studies have assessed children's behaviours over multiple years . Objective To examine children's obesogenic behaviours during spring and summer of the COVID‐19 pandemic compared to previous data collected from the same children during the same calendar period in the 2 years prior. Methods Physical activity and sleep data were collected via Fitbit Charge‐2 in 231 children (7–12 years) over 6 weeks during spring and summer over 3 years. Parents reported their child's screen time and dietary intake via a survey on 2–3 random days/week. Results Children's behaviours worsened at a greater rate following the pandemic onset compared to pre‐pandemic trends. During pandemic spring, sedentary behaviour increased (+79 min; 95% CI = 60.6, 97.1) and MVPA decreased (−10 min, 95% CI = −18.2, −1.1) compared to change in previous springs (2018–2019). Sleep timing shifted later (+124 min; 95% CI = 112.9, 135.5). Screen time (+97 min, 95% CI = 79.0, 115.4) and dietary intake increased (healthy: +0.3 foods, 95% CI = 0.2, 0.5; unhealthy: +1.2 foods, 95% CI = 1.0, 1.5). Similar patterns were observed during summer. Conclusions Compared to pre‐pandemic measures, children's PA, sedentary behaviour, sleep, screen time, and diet were adversely altered during the COVID‐19 pandemic. This may ultimately exacerbate childhood obesity.

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Background Careful consideration and planning are required to establish “sufficient” evidence to ensure an investment in a larger, more well-powered behavioral intervention trial is worthwhile. In the behavioral sciences, this process typically occurs where smaller-scale studies inform larger-scale trials. Believing that one can do the same things and expect the same outcomes in a larger-scale trial that were done in a smaller-scale preliminary study (i.e., pilot/feasibility) is wishful thinking, yet common practice. Starting small makes sense, but small studies come with big decisions that can influence the usefulness of the evidence designed to inform decisions about moving forward with a larger-scale trial. The purpose of this commentary is to discuss what may constitute sufficient evidence for moving forward to a definitive trial. The discussion focuses on challenges often encountered when conducting pilot/feasibility studies, referred to as common (mis)steps, that can lead to inflated estimates of both feasibility and efficacy, and how the intentional design and execution of one or more, often small, pilot/feasibility studies can play a central role in developing an intervention that scales beyond a highly localized context. Main body Establishing sufficient evidence to support larger-scale, definitive trials, from smaller studies, is complicated. For any given behavioral intervention, the type and amount of evidence necessary to be deemed sufficient is inherently variable and can range anywhere from qualitative interviews of individuals representative of the target population to a small-scale randomized trial that mimics the anticipated larger-scale trial. Major challenges and common (mis)steps in the execution of pilot/feasibility studies discussed are those focused on selecting the right sample size, issues with scaling, adaptations and their influence on the preliminary feasibility and efficacy estimates observed, as well as the growing pains of progressing from small to large samples. Finally, funding and resource constraints for conducting informative pilot/feasibility study(ies) are discussed. Conclusion Sufficient evidence to scale will always remain in the eye of the beholder. An understanding of how to design informative small pilot/feasibility studies can assist in speeding up incremental science (where everything needs to be piloted) while slowing down premature scale-up (where any evidence is sufficient for scaling).

Positive parent-child attachment can be determined by opportunities for the child to interact with his/her parent and can influence a child's physical activity (PA) behavior. Therefore, an intervention that provides children and their parent more time to interact positively could impact children's PA. We examined the efficacy of a 12-week mother-daughter intervention on African-American girls' PA levels. In Spring of 2013 and 2014, mother-daughter dyads (n = 76) from Springfield, MA, were randomly assigned to one of three groups [child-mother (CH-M, n = 28), child alone (CH, n = 25), or control (CON, n = 23)] that participated in an afterschool culturally-tailored dance intervention (60 min/day, 3 days/week, 12 weeks). Girls in the CH-M group participated in the intervention with their maternal figure, while girls in the CH group participated in the intervention alone. CON group participants received weekly health-related newsletters. PA was assessed with accelerometers for seven days at baseline, 6-weeks, and 12-weeks. Hierarchical linear modeling was used to examine rates of change in PA. During the afterschool intervention time, girls in the CH-M group displayed a significantly steeper rate of increase in their percent time spent in vigorous PA compared to both the CON (γ = 0.80, p < 0.001) and the CH group (χ2 (1)=13.01, p < 0.001). Mothers in the CH-M group displayed a significantly steeper rate of increase in their percent time spent in total daily moderate-to-vigorous PA compared to CH group's mothers (γ = 0.07, p = 0.01). This culturally-tailored mother-daughter afterschool intervention influenced African-American girls' afterschool hour PA levels, but not total daily PA.Trial Registration: Study is registered at www.clinicaltrials.govNCT01588379.