In the last 10 years, there has been a marked increase in the prevalence of obesity in children beginning at 3-4 years of age. The only realistic solution to the problem is prevention. Although there is limited evidence for the effectiveness of preventive programmes, there is a consensus that multisectorial action is urgently needed. This should include intervention at the family, school, municipal, regional and national levels, including the commercial sector and food companies. Treating childhood obesity has not been very successful, but some comprehensive community-based treatment programmes have shown reasonable long-term results. There is a need to establish such community-based treatments with emphasis on psychological aspects.