When you are thinking of food, you probably won't immediately think of waste of ressources. Especially not of unnecessary waste of ressources, because all of us HAVE to eat. But just because everyone always has to eat, it contributes so much to the use of energy.
According to the UNEP report "Priority products and materials" 31 % of our impacts on global warming coming from consumption, belongs to food.[http://www.unep.fr/shared/publications/pdf/DTIx1262xPA-PriorityProductsAndMaterials_Report.pdf] Therefore food is the biggest contributor, even greater than transport or electrical devices.
However the waste of energy and ressources are not equal for all kinds of food. CO_2 emissions, use of water, land use, energy consumption... of animal products are much higher than those of plant products.
[According to the study "Diet and the environment: does what you eat matter?" of Marlow HJ et. al. a non-vegeterian diet uses 2.9 times more water, 2.5 times more primary energy and 13 times more fertilizer than a vegeterian diet http://www.ncbi.nlm.nih.gov/pubmed/19339399]
Therefore we mostly eat vegeterian (for us that means not eating meat, chicken and fish) and try to reduce our consumption of animal products.
But still every human needs a balanced diet. Especially when you do sports for 8 hours aday. We want to test, if we feel good and active with a low-animal product diet.