The Eatwell for the Planet campaign wants to see a change to official UK government dietary advice - which is embodied in the Eatwell Plate, a picture representation of what a balanced diet should look like. They want the Eatwell Plate to take into account the interdependency of public health and environmental health. Take a look at Sustain's guidelines on eating more sustainably.
Sustain: Sustain The alliance for better food and farming advocates food and agriculture policies and practices that enhance the health and welfare of people and animals, improve the working and living environment, enrich society and culture and promote equity.