The theory is our bodies were designed, and still optimized, to eat what our Paleolithic ancestors ate. Like your hunger-gatherer forefathers, on Paleo you get all the meat from wild animals and unlimited fruits and vegetables you can eat. But no starchy vegetables (like potatoes), no legumes (like lentils or beans), no wheat, and no grains (like quinoa or corn) because those plants were invented by human beings during the agricultural revolution after our Paleolithic ancestors left the planet. You get one cheat day where you can eat whatever you want (“Occasional cheating and digressions may be just what you need to help you stick to the diet.”) No oil because it puts omega 6 and omega 3 ratios out of whack which should never exceed 2:1, except olive oil if you must. Dairy is also prohibited. And meat must come from animals that weren’t fed grains (like corn) because grains lead to inflammation and increased fat.
The Soft Science of Dietary Fat is a summary of an article in Science Magazine reporting that mainstream nutritional science has demonized dietary fat, yet 50 years and hundreds of millions of dollars of research have failed to prove that eating a low-fat diet will help you live longer. In fact, there are good reasons to believe high-carbohydrate diets may be even worse than high-fat diets. Here is the text from the original article by Gary Taubes.
Anyone and everyone that has come through the bay doors at CFA will answer this question "what is your favorite part about CFA?" the same: the people. From all walks of life. In all shapes and sizes. All ages. And without exception, everyone is a genuinely good person. The camaraderie experienced at CFA is the first time since high school athletics that I’ve felt like I was a part of something bigger than myself.
The Paleo Diet focuses on foods that are high in protein, low in carbs, and rich with fiber. There's a strong emphasis on meat, fruits, and vegetables — basically, anything our ancestors would have consumed more than 10,000 years ago during the Paleolithic era. (There's actually some truth to this: in July 2018, when researchers identified the stomach contents of the 5,300-year-old mummy Otzi, they found that his last meal was high-fat and contained "animal and plant remains," making it pretty Paleo-friendly.)
It should be noted that U.S. News & World Report just released its annual ranking of diets, and Whole30 ranked dead last. Why? Essentially, the expert panel of over 20 registered dietitians, academics, and medical doctors found the program unsustainable and potentially unhealthy, since, among other issues, it restricts certain food groups and is high in sodium and cholesterol. But, Whole30's co-creator Melissa Hartwig stands behind the program, telling Cosmopolitan.com that its animal protein recommendations are in line with government recommendations, and that there are no nutrients in temporarily restricted foods, like grains and legumes, that you can't find in fruits and vegetables.
You’ll lose weight because any time you restrict entire food groups, your calorie intake tends to be lower, Sandon says. And whenever you burn more calories than you consume, you'll have weight loss, she says. (2) The focus on lean protein, fruits, and vegetables over calorie- and sodium-rich processed foods can also contribute to weight loss, though she also points out that the paleo diet wasn’t created to be a weight loss diet. (3)
A metaresearch group at Tilburg University in the Netherlands investigates scientists’ research methods and operations, scrutinizing questionable practices such as selective reporting of statistical tests and data massaging. The group instead advocates for practices such as preregistering studies and making experimental data immediately available for open external review and verification. Its members are optimistic that “the perverse incentives of careerist academia, to hoard data and sacrifice rigor for headline-generating findings, will ultimately be fixed.”