Food system activities are inextricably linked with climate and weather, environmental resources and human health. This article reviews the contribution of food system activities to climate change, the positive feedback on food systems and the effects of dietary change on food system outcomes. It combines a systematic literature review with analyses of publicly available international data. The article shows that whereas emissions from food production continue to increase in most regions, emissions from land use change have been decreasing. Despite these decreasing trends, emissions from land use change are huge and in some regions are greater than emissions from food production. Climate change also affects food system activities and there is strong scientific consensus that it negatively affects food production, especially in Africa and Asia. However, from the available scientific evidence, the impacts of climate change on post-production activities are unclear. The article also shows that dietary change as a transformation strategy has large potential for reduction of greenhouse gas emissions but, regionally, is associated with substantial environmental trade-offs.