Originally Answered: What is the paleo diet?
The Paleo diet is pretty simple.
Our genetic ancestors, going all the way back to Homo erectus, did not farm animals nor harvest grain. He pulled food from trees, scavenged it from the kills of carnivores, and dug roots and greens to eat. Later on, after fire was able to be controlled, he started cooking more foods (like meat) but still did not eat dairy, could not have eaten nightshades (tomatoes, peppers & potatoes--all from the American continents) nor corn, and did not eat vegetable oils or grains (except occasionally--even then that tended to occur in the Upper Paleolithic period, which came right before the Neolithic, aka "agricultural" period).
Some folks say that the "caveman" diet was comprised mostly of meat, but in all honesty that was most likely not the case (it just sounds cool). However, the caveman would never have passed up an opportunity for fresh meat, especially when he developed the skills needed to bring down an animal for himself or his group. He did not shy away from fat, the organs, or bone marrows since those were very high in nutrients and contained loads of calories to keep him going. He also did not eat 3 square meals a day, and in the beginning might have been lucky to have one good meal a day. He ate when he was hungry, not when the sun's position in the sky told him he SHOULD eat.
Look at the rising obesity rates in developed countries. At the number of cases of those with grain and lactose intolerance, or diseases that are aggravated by consuming these products. Heart disease is rampant, and it's not because people are eating more meat now. It's because the ADA constructed the "Food Pyramid" which has grains as the base. The correlation between a grain-based diet and heart disease is obvious when you make that connection.
Commercially-raised livestock today don't contain the same ratios of nutrients that the wild-caught game does. Meats today are high in Omega-6 fatty acids, which tip the balance that Omega-3 and Omega-6 needs in order to maintain a healthy body. Grass-fed meats are the way to go. Pork should be uncured (no nitrates). Look for eggs that are cage-free and high in Omega-3. Buy organically (and locally if possible) veggies. Not just to reduce the ingestion of pesticides but also to ensure that your food has the highest mineral/vitamin content possible. Avoid foods with "fake" ingredients, like HFC (high fructose corn syrup), vegetable oils and processed sugars. Reduce or eliminate salt (salt was a rarity back then--only people living along the coast had a regular supply of it).
I started Paleo as a way to eat healthier. It's one of the few sustainable diets that exists, and meats all of your nutritional needs with minimal effort. Within 3 weeks I'd lost 5 lbs, and I don't even exercise. I'm at a healthy 120lbs, 28 years old and 5'4".
Yes, it's so easy that even a caveman did it ;)