The carnivore diet (also called a zero carb diet) is a high-protein fad diet in which only animal products such as meat, eggs, and dairy are consumed. The carnivore diet is associated with pseudoscientific health claims. The diet lacks dietary fiber, can lead to deficiencies of vitamins, and can increase the risk of chronic diseases. The lion diet is a highly restrictive form of the carnivore diet in which only beef is eaten.

The idea of an exclusive meat diet can be traced to the German writer Bernard Moncriff, author of The Philosophy of the Stomach: Or, An Exclusively Animal Diet in 1856, who spent a year living on only beef and milk. In the 1870s, Italian physician Arnaldo Cantani prescribed his diabetic patients an exclusive animal-based diet. In the 1880s, James H. Salisbury advocated a meat diet consisting of 2 to 4 pounds of lean beef and 3 to 5 pints of hot water daily for 4 to 12 weeks. It became known as the meat and hot water diet, or Salisbury diet.

In 2018, the carnivore diet was promoted on social media by former orthopaedic surgeon Shawn Baker, who wrote the book The Carnivore Diet. Jordan Peterson and his daughter Mikhaila Peterson were also vocal adherents of this diet. Peterson and his daughter follow a strict type of carnivore diet termed the lion diet, in which only beef, salt, and water are consumed. The 'lion diet', which became a viral fad on TikTok, is described by experts as "being potentially very unhealthy, is difficult to follow and unsustainable in the long term".

In April 2023, skeptic and neurologist Steven Novella described the carnivore diet as the latest fad diet to have achieved popularity. Because of its high cost Novella described the diet as one for "select elites", adding what he said was a further unsavory aspect to its harmful and pseudoscientific basis. The carnivore diet advertised by meat influencers on social media platforms has been described as a fringe movement.

People following a carnivore diet consume high-protein animal-based products, such as beef, pork, poultry, and seafood. Some may eat dairy products and eggs. All fruits, legumes, vegetables, grains, nuts and seeds are strictly excluded.

The carnivore diet is often confused with Inuit cuisine. Primary differences include a high proportion of organs in the Inuit diet, high seafood content, and consumption of raw meat, all of which are not typical for the fad carnivore diet. Inuit cuisine is also not exclusively composed of animal products, as the Inuit would consume plant products they acquired from gathering.

There is no clinical evidence that the carnivore diet provides any health benefits. Dietitians dismiss the carnivore diet as an extreme fad diet, which has attracted criticism from dietitians and physicians as being potentially dangerous to health (see Meat § Health).

It also raises levels of LDL cholesterol, which increases the risk of cardiovascular disease. While carnivore diets exclude fruits and vegetables which supply micronutrients, they are also low in dietary fiber, possibly causing constipation. A carnivore diet high in red meat increases the risks of colon cancer and gout. The high protein intake of a carnivore diet can lead to impaired kidney function.

Criticism also derives from concerns about greenhouse gas emissions associated with large-scale livestock farming required to produce meats commercially, and the potential for such emissions to worsen climate change (see environmental impact of meat production).

• Carnivore
• Lectin-free diet
• Monotrophic diet
• Paleo diet