RESUMO
OBJECTIVE: To summarise the main results of a community-based study on physical activity promotion - "Romsås in Motion". METHODS: The study assessed changes in physical activity, body mass and psychosocial mediators of physical activity from a pseudo-experimental cohort study involving two districts with low socioeconomic status in Oslo, Norway. In 2000, baseline investigation included 2950 30-67-year-olds - 48% of those invited. At follow-up in 2003 we measured 1776 subjects (67% of those eligible). A set of theoretically informed strategies targeting individuals, groups and the environment were implemented, tailored towards groups with different psychosocial readiness for change. Net changes (the difference between changes in the intervention and control districts) and results of mediation analyses related to the effect of the intervention are reported. RESULTS: The increase in physical activity measured by two questionnaires was 9.5% (p = 0.008) and 8.1% (p = 0.02), respectively. The proportion who increased their body mass was reduced by 50% compared with the control district. Participation in walking and aerobic exercise groups, having seen the "Walk the stairs" poster and used the walk path, were particularly effective intervention components. The most promising psychosocial mediators of forward transition in stages of change were physical activity identity, perceived control, support from friends and family, and self-efficacy when facing psychological barriers. CONCLUSION: Through a theoretically informed, low-cost, population-based intervention programme an increase in physical activity levels and a reduced weight gain were observed. Mediation findings regarding forward transition in stages of change enhance our understanding of psychosocial mechanisms of behaviour change, and may prove helpful in guiding implementation and evaluation of future interventions.