The Paleo Diet, or, as some call the "caveman" diet, has on its menu what humans are thought to have eaten during the Paleolithic era. The list consists of the kinds of foods that ancient humans might have hunted, fished, and gathered, and avoid foods that were from the more modern era. You avoid processed foods and drink plenty of water. The idea behind paleo is that those highly processed foods lead to obesity, diabetes, and heart problems with all the added fats, sugars, and who knows what else. Many people believe that a simpler, basic diet, like early humans used to eat, could be better for your health.