Atypical vegan diet has the lowest average carbon footprint (3.0 pounds of carbon dioxide equivalents per 2,000 calories), followed by vegetarian (5.1), pescatarian (7.3), omnivore (9.8), paleo (11.6), and keto (12.8) diets, scientists estimated. A Mediterranean (4.3) or DASH (8.1) diet beat other omnivore diets.