When you hear the words paleo or caveman, you probably think of a huge slab of meat sizzling over a campfire. But, truth be told, you can be a vegetarian and thrive on a paleo-style diet. "There's no obligation to eat meat," says Mark Sisson, author of 'The Primal Blueprint.' "It's just a lot easier when you consume animal products." The overarching paleo principle is to stop eating food that's made in factories – in other words, eat only whole foods. When you do, you cut out sugar, refined carbs, and industrial oils. As a vegetarian, you can load up on eggs, nuts, dairy, beans, and tofu – the last three aren't endorsed by all followers, but you need protein. If you don't eat eggs or dairy, you can still be paleo, but supplement with vitamin B12, found in animal foods and crucial to metabolism and brain function. Since over-the-counter vitamins aren't very bioavailable, or easily assimilated by the body, get a B12 injection from a doctor every few months. Also, take a good omega-3 supplement from fish or krill that contains both EPA and DHA, and a multivitamin with zinc, iron, and vitamin D.