Livewell report for WWF by Rowett institute

Looks at UK dietary changes to achieve a reduction of Greenhouse Gas emissions  of 28% by 2020 and 75% by 2050    It concludes
The report’s key messages are that a diet can be achieved which meets dietary recommendations for health and the GHG reduction targets for 2020, without eliminating all meat and dairy products. Rebalancing the UK diet in line with the Eatwell plate and reducing meat-based proteins could achieve a diet that would meet the 2020 GHG target. Meeting the GHG targets for 2050 and dietary recommendations will require a radical shift in food consumed, though it would be possible to include some meat or dairy products in very small amounts if other food in the diet were low in GHGs.
Broadly the diet recommends eating more seasonal, regionally grown fruit and vegetables; eating less meat (red and white) and eating less highly processed foods which are more resource-intensive to produce. It points out that this report just looks at nutrition in relation to  GHG emissions and that more work is needed to integrate wider issues of sustainability into the modelling process and to develop broader dietary advice.
http://www.fcrn.org.uk/fcrnPublications/publications/PDFs/howlow/WWF_How_Low_Summary.pdf