Associations between the "Double Reduction" policy and physical activity and overweight/obesity among Chinese school-aged children: a quasi-experimental difference-in-differences analysis

In July 2021, China implemented the "Double Reduction" policy to ease homework burden and curb off-campus tutoring for students in compulsory education. The policy has been evaluated mainly for academic and mental health outcomes; whether it coincided with changes in physical activity and weight status is unclear. This study used the policy as a natural experiment to examine associations between the Double Reduction policy, moderate-to-vigorous physical activity (MVPA), and overweight/obesity among Chinese school-aged children.

We analyzed the 2018, 2020, and 2022 waves of the China Family Panel Studies (CFPS) in a quasi-experimental difference-in-differences (DiD) design. At each wave, students enrolled in compulsory education (grades 1-9) formed the treatment group and senior high school students (grades 10-12), who were not covered by the policy, formed the comparison group. The analytical sample comprised 4,237 students contributing 10,799 person-wave observations. Outcomes were self-reported weekly MVPA minutes and overweight/obesity defined by age- and sex-specific body mass index z-scores (WHO 2007 reference). Event-study specifications, propensity-score weighting, longitudinal survey weights, and placebo tests assessed the stability of the estimates.

The policy was associated with 43.1 additional MVPA minutes per week (95% CI: 33.8-52.3; p < 0.001) and a 3.9 percentage-point reduction in overweight/obesity (95% CI: -7.2 to -0.6; p = 0.022) among compulsory education students relative to the comparison group. Estimates were larger among primary school students and among children whose parents had lower educational attainment. The 2018 pre-policy interaction was small and not statistically significant for either outcome, although two pre-policy waves offer limited power for testing pre-trends. Estimates were similar under balanced-panel, propensity-score-weighted, survey-weighted, and placebo specifications.

The Double Reduction policy coincided with measurable improvements in physical activity and weight status among Chinese school-aged children. Education policies that relieve academic burden may carry collateral public health benefits and deserve explicit consideration in child health strategies.