Researchers at Trinity College Dublin found 16% of children in schools that used a healthy schools programme were obese, compared with 25% in schools that did not.
Almost three out of four children who took part in the programme were within their normal weight, compared with 58% of children in the control schools’ group.
The programme was co-ordinated by the Childhood Development Initiative (CDI) in seven primary schools in Tallaght, Dublin, from 2009 to 2011.
The programme aimed to improve both children’s and teachers’ understanding and practice relating to diet, exercise and mental health.
The study also found that children in schools where the programme was run had better social support and relations with their class mates.
Author TCD professor Catherine Comiskey said the follow-up study showed it took a number of years for the benefit of a health-focused intervention to become evident.
Alex White, the minister of state with responsibility for primary care, said that the Government would use the findings to see how best to support and enhance young children’s health.
Marian Quinn, the CDI chief executive, said that intervention programmes needed to be embedded in school policy and ethos, rather than an add-on for teachers, to be successful.
Last autumn CDI was selected as part of the Government’s Area-Based Childhood (ABC) Programme, which is co-funded by Atlantic Philanthropies.