The Paleolithic diet, Paleo diet, caveman diet, or stone-age diet is a modern fad diet consisting of foods thought by its proponents to mirror those eaten by humans during the Paleolithic era.
The diet avoids processed food and typically includes vegetables, fruits, nuts, roots, and meat and excludes dairy products, grains, sugar, legumes, processed oils, salt, alcohol, and coffee. Historians can trace the ideas behind the diet to "primitive" diets advocated in 19th century. In the 1970s Walter L. Voegtlin popularized a meat-centric "Stone Age" diet; in the 21st century the best-selling books of Loren Cordain popularized the Paleo diet.
In the 21st century, the sequencing of the human genome and DNA analysis of the remains of early humans have found evidence that humans evolved rapidly in response to changing diet. This evidence undermines a core premise of the paleolithic diet - that human digestion has remained essentially unchanged over time. Anthropological science has found that human diets in paleolithic times were more varied and less meat-centric than had previously been assumed.
Advocates promote the paleolithic diet as a way of improving health. There is some evidence that following it may lead to improvements in body composition and metabolism compared with the typical Western diet or compared with diets recommended by some European nutritional guidelines. On the other hand, following the diet can lead to nutritional deficiencies such as an inadequate calcium intake, and side effects can include weakness, diarrhea, and headaches.