Bill Clinton declares vegan victory

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

He talked about his plant-based diet last year, saying he lost 24 pounds on it for his daughter Chelsea's wedding, and he chatted about it again recently on TV, drawing national attention to the potential health benefits of this type of diet.

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

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.