Day 1 of the vegan challenge kicks off with Kathy Freston's workshop. The studio is filled with 375 eager—and a few skeptical—participants. "I think the Harpo staff is really up for this challenge," Lisa says. "We're a bit of a different group here. We're all overachievers. So I think that because they said they're going to do it, they're going to do it."

Watch Lisa counsel supervising senior producer Jill through a vegan dinner roadblock