Getting fit by doing good: Exercise, volunteering, and mental health at scale.

Community-based lifestyle interventions combining physical exercise with volunteering are promoted as low-cost, scalable support for those with mental health problems, and feature prominently in social prescribing. Yet robust evidence that they are effective at scale, outside controlled trials, remains scarce. We evaluate a nationwide UK intervention that combines exercise and volunteering in local communities. Using three waves of incentivised surveys (February 2023 to March 2024; 3590 observations from 2856 respondents) linked to administrative data on participation, we compare participants with those who signed up but did not participate, including for plausibly exogenous reasons. Participation is associated with lower mental ill health and loneliness, and higher feelings of belonging, connectedness, and trust. The estimates are sizeable and persist beyond six months. Benefits substantially exceed costs. Our findings suggest that community-based exercise and volunteering can deliver meaningful mental health improvements at low cost and at scale, offering policy-makers a cost-effective means of relieving pressure on stretched health services.