Former President Bill Clinton, known around the world for his love of burgers, barbecue and greasy junk food, has gone from a meat lover to a vegan, the strictest form of a vegetarian diet.  Clinton says he now eats fruits, vegetables and beans, but no red meat, chicken or dairy.

Clinton, 65, who had quadruple bypass surgery in 2004 and then stent surgery in 2010, says he is following this eating plan to improve his heart health.

Vegetarians and Vegans have a lower risk of heart disease and cancer, especially colon cancer, and they tend to live longer, and they're less likely to be overweight.

About 3% of U.S. adults are considered full-fledged vegetarians because they never eat meat, poultry, fish or seafood, and about 1% of people are vegans because they also never eat dairy, eggs or honey, says the Vegetarian Resource Group.

"The percentage of vegetarians has doubled since 1994," says John Cunningham, consumer research manager for the organization.

"Veganism is the most extreme type of vegetarianism," says Marion Nestle, a nutrition professor at New York University.

Bill Clinton says he was inspired to follow a low-fat, plant-based diet by several doctors, including  Dean Ornish, author of Dr. Dean Ornish's Program for Reversing Heart Disease.  Ornish has been working with Clinton as one of his consulting physicians since 1993.