Greenhouse gas emissions associated with the food we eat are one of many environmental impacts associated with our diet. The emissions are a byproduct of the energy and chemical inputs associated with growing, transporting and processing the food plus the emissions from the plants and animals themselves. This study quantifies the greenhouse gas emissions (in CO2 equivalents) of the average American diet, as well as the diet recommended by the USDA for traditional, lacto-ovo-vegetarian, and vegan diets. Meat and seafood constitute about 16% of the 2,543 calories of the average American diet, but contribute about 61% of this diet’s daily greenhouse gas emissions. A 1% reduction in greenhouse gas emissions is expected when switching from the average diet to the recommended 2,000 calorie diet. A 33% reduction in greenhouse gas emissions is expected when switching from the recommended diet to a vegetarian diet, and an additional 25% reduction is expected when switching to a vegan diet. Making informed changes in one’s diet can be an easy, healthy, and affordable way to reduce one’s carbon footprint.