While a vegetarian diet often includes animal products that aren’t flesh (eggs and milk, for example), a vegan diet excludes anything that ever had anything to do with an animal (although many simulated animal products, like soy cheese and vegetable protein meat, are available). Many people who choose a vegan diet are animal lovers who reject eating animal products for ethical reasons. A vegan diet can lower one's carbon footprint as well.
Studies confirm that vegans tend to eat fewer calories, weigh less, and have a lower body mass index than their omnivorous counterparts. Eating a lot of produce and whole grains leads to the feeling of fullness with fewer calories. But there are plenty of processed foods that fall into the vegan category, which can be a problem if protein and fiber are being replaced with, say, French fries. Also, eliminating animal-based food products may leave vegans vulnerable to deficiencies in calcium, vitamins B-12 and D — however, with a little planning, these are easily added back to the diet.