The interactions between movement behaviors (physical activity, screen time, and sleep) affect the health of preschool children. Therefore, we examined the status of adherence to combinations of 24-hour movement guidelines (24-h MG) in Japanese preschool children and determined the associations between overweight/obesity and adherence to these 24-h MG. This cross-sectional study was conducted with 421 children aged 3–5 years (216 boys and 199 girls) living in the northeastern region of Japan. To evaluate the 24-h MG, physical activity over one week was measured using a three-axis accelerometer. For screen time and sleep duration, a questionnaire survey was conducted. Children who failed to meet all the 24-h MG had a higher probability of overweight/obesity than those who met all the 24-h MG (odds ratio 1.139, 95% confidence interval: 1.009, 1.285). The percentage of adherence to the 24-h MG was 91.6% for physical activity, 82.5% for sleep duration, and 33.7% for screen time, and only 21.5% of the children adhered to all three areas of the guidelines. Our findings have important implications for developing public health policies and effective intervention programs for preschool children.

There are few studies comparing adherence to Canadian 24-hour Movement Guidelines (24-h MG) before and during the COVID-19 pandemic and exploring the pandemic’s effect on childhood obesity. This survey-based 2-year study investigated changes in obesity and adherence to the 24-h MG in children before and during the COVID-19 pandemic. Data were collected at two points in time: pre-COVID-19 (May 2019; T1; n = 247) and during-COVID-19 (May 2021; T2; n = 171). Participants were healthy elementary school children aged between 6–12 years in northeastern Japan. The questionnaire comprised items on physical activity, screen time, sleep duration, adherence to the 24-h MG, and anthropometric and demographic characteristics. Among all participants, a statistically significant difference (p < 0.001) between the average body mass index at T1 (M = 16.06 kg/m², SD = 2.08 kg/m²) and T2 (M = 18.01 kg/m², SD = 3.21 kg/m²) was observed, where 17.8% were overweight and obese at T1 and 24% at T2, and 10.9% adhered to all 24 h MG at T1 and 4.1% at T2. To prevent obesity in children during the COVID-19 pandemic, environmental changes should be evaluated and appropriate preventive measures taken, including pro-community health programs that encourage parent-children outdoor activities.