Veganism is the elimination of all animal products from the diet. Vegans (as followers of veganism are called) shun all foods that are derived from animals. This includes not only meat and seafood, but also milk, butter, eggs and even honey.
According to a 2009 survey by the Vegetarian Resource Group, about 1 percent of Americans are vegans.
When invented: The Hindu concept of ahimsa, or non-violence to all living things, necessitates a vegan diet and has been around for millenia. The term "vegan" was coined in 1944 in the United Kingdom and America's first Vegan Society was founded in California in 1948.
Length of diet plan: Veganism is meant to be a lifelong commitment. Hardcore vegans avoid not only animal-based foods but animal-based clothing and medicines as well.
Alicia Silverstone and Lea Michele are well-known vegans. Michael Pollan, the famed food writer, eats two vegan meals a day—he describes this diet as "vegan until dinner."