Universal free school meals and children's bodyweight. Impacts by age and duration of exposure.

We study the impact on children's bodyweight of switching from means-tested to universal provision of nutritious free school meals in England. We exploit the roll-out of universal provision across Local Authorities to estimate effects at different ages and durations of exposure, based on nurse-collected, population-wide health data for state school children. Exposure to universal free lunches reduces obesity prevalence and BMI among children aged 4-5 and 10-11, but older children's bodyweights are less responsive than younger children's. We find tentative evidence that effects may be cumulative, as impacts are largest for those exposed to universal free school meals throughout primary school.