Restrictive diets are not new to the weight-loss world. The cabbage soup and grapefruit diets are as famous as the Master Cleanse (a juice fast of water, lemon juice and—if you can stomach it—cayenne pepper). But among these mono diets, the carnivore diet is the newest kid on the block. In the shadow of the more popular keto and paleo diets, the carnivore diet has quietly emerged with a dedicated following and big promises. Here we take a look at what the diet entails, what the health benefits and downsides are, and if it's safe to try.
The carnivore diet, also known as the zero-carb diet, is an eating style that incorporates animal products only. That means there's room on the plate for meat, organs, butter and eggs, but vegetables, fruit, grains and other plant foods are off-limits.
Some dairy products are also allowed, such as yogurt and milk, but strict carnivore dieters may eschew them because they contain lactose, a naturally occurring sugar that does add carbs.
"The carnivore diet consists only of animal-derived foods and nothing that comes from plants," says Summer Yule, M.S., R.D.N., a registered dietitian in Connecticut.
If the carnivore diet sounds like the popular keto diet to you, that's not surprising. In reality, the two diets do share some characteristics: both involve eating very limited or no carbs. Plant foods are almost, if not entirely, eliminated too.
Unlike the carnivore diet, the keto diet emphasizes eating high amounts of fat and moderate amounts of protein. The carnivore diet does not make that distinction and does not encourage daily goals for any particular nutrient.
"While both diets are low in carbohydrates and high in fat, keto allows for non-animal foods from plant sources, such as nuts, seeds, some fruits—avocado and berries mainly—and nonstarchy green vegetables," says Molly Devine, R.D., L.D.N., founder of Eat Your Keto.
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The list of approved foods for the carnivore diet is short. The foods primarily fall into one category: meat. Some carnivore diet plans also allow for dairy foods, such as milk and yogurt.
• beef and red meat
• bone marrow
• chicken and poultry
• fish and seafood
• organ meats
• bone broth
"Organ meats are a vital way to get vitamins and minerals you might miss since you're not eating fruits and vegetables," Devine says. "Organ meats, such as liver and heart, provide essential micronutrients that would otherwise be lacking due to the absence of plant products like fruits and veggies."
"Some versions of the diet also allow some dairy products since they technically come from animals," Devine says.
However, these foods contain lactose, a type of sugar. That means these foods have some carbohydrates. For dieters aiming to keep carbs as close to zero as possible, dairy foods may be not worth the carbs.
• any source of carbohydrates, such as sugar
• artificial sweeteners
Some carnivore dieters believe that grains, legumes and seeds contain "antinutrients," plant compounds that prevent the body from absorbing vitamins and minerals. Research says antinutrients aren't harmful, and most are destroyed in the cooking process or by your gut during digestion.
Some carnivore dieters also believe all fruits and vegetables are toxic to the body.
"The carnivore diet leaves out plant-based foods that contain important nutrients like fiber, potassium, folate and vitamin C, which are important for gut, heart and immune system health," says Staci Gulbin, M.S., M.Ed., R.D., L.D.N.
That's why many nutrition experts and dietitians do not support the carnivore diet.
"Vegetables and fruits are essential to a healthy diet because they are packed with electrolytes like magnesium, iron, calcium and fibers to support healthy digestion and intestinal flora, plus all the vitamins and antioxidants," says Luiza Petre, M.D., a weight-loss and weight-management specialist and board-certified cardiologist. "While starches are not necessarily essential, fiber- and vitamin-rich vegetables should not be excluded."
Shawn Baker, an orthopedic surgeon and author of The Carnivore Diet, is credited with much of today's meat-only diet hype. (Baker had his medical license revoked in 2017.) Mikhaila Peterson, daughter of lifestyle guru Jordan Peterson, is also an advocate for the plan. She says following this diet relieved her symptoms of depression and eliminated her arthritis.
These two are among a chorus of individuals who believe in the carnivore diet. They suggest that the diet can eliminate symptoms of chronic and inflammatory diseases and provide more energy and greater well-being. Other proposed benefits include:
• Feeling better. Many carnivore dieters report greater energy and concentration after several days on the diet. (This is a common benefit ascribed to the keto diet as well.) "The elimination of all processed foods, sugars and refined carbohydrates is a big pro," Devine says. "However, this is a very restrictive way of eating that is not sustainable for most people."
• Cleaner diet. Sugar, refined carbs and processed foods are out with the carnivore diet. "The carnivore diet cuts out processed and refined carbohydrates, ensures plenty of protein intake and promotes water consumption," Gulbin says. That's still not reason enough for Gulbin to recommend the diet. "It leaves out plant-based foods that contain important nutrients like fiber, potassium, folate and vitamin C that are important for gut, heart and immune system health."
• Fewer food sensitivities. If you believe you have food allergies or sensitivities, you may find they disappear with the carnivore diet. That's because the diet does not contain food groups that are most likely to offend allergies or food issues.
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You could. Eating very few or no carbs will naturally put your body into ketosis, a state in which your body is forced to burn fat for fuel instead of relying on available carbohydrates. You'll lose water weight at first. Then, the increased demand on fat could lead to real weight loss.
"Ketosis has its own health benefits and leads to weight loss," Petre says.
But in order for ketosis to be done properly, you have to eat a wider variety of foods without noshing on burgers and brats alone.
"Even though protein is one of the most important nutrients you consume daily, it has consequences when overdone. Protein is required to repair and build muscle, boost immunity, give us energy, help process nutrients, and it keeps you feeling full," Petre says. "The problems arise when you get too much of a good thing. Eating too many proteins and going above the calories needed on a daily basis can lead to weight gain, as the excess intake gets converted into fat and stored."
For example, red meat is pretty high in fat and calories compared to lean protein options like fish and chicken. One ounce of red meat can be 75 calories. A 6-ounce steak sirloin has 450 calories.
Petre adds, "High-protein diets will satiate you, but if you consume too many animal proteins, you could tip the scales the wrong way."
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Currently, there are no studies that have looked at the effects of this diet. Most reports of success (or failure) are anecdotal. That's the case with Shawn Baker and Mikhaila Peterson.
"There are no long-term studies on humans using this diet," Yule says, "so I am not comfortable recommending this diet at this time."
In fact, to find any science about this style of eating, Yule says you have to look back almost 100 years to 1930 to a report in which two men ate an all-meat diet for one year.
"They did not lose weight on the diet except some initial water weight," she says. "Neither developed vitamin deficiencies, but they were consuming items such as calf brain and liver. Unlike most meats, these organ meats contain a fair amount of vitamin C, which could have helped protect these men from deficiencies."
An earlier report from 1886 documented a man who lost weight and reported decreased indigestion after a six-week carnivorous-style diet.
However, Gulbin cautions, it's unclear what long-term effects this diet has on overall health.
Without research to determine the effects of this diet, the benefits as well as the risks are based largely on anecdotes and previous research around heavy meat consumption. Possible health risks include:
• Risk for nutrient deficiencies. Vitamins, fruits and other plant foods are chock-full of nutrients that research says help you live a longer, healthier life. It's unclear if vitamin-rich meat sources can adequately make up for this lost nutrition. "This diet lacks phytonutrients, many of which are associated with reduced risk of chronic disease," Yule says. "It is also lacking in prebiotics. Prebiotics help support the good bacteria in our gut."
• Potential kidney problems. "Dehydration occurs when your kidneys are overworked by removing nitrogen waste and excess proteins from metabolizing the protein, causing you to urinate in excess," Petre says. She says this process will eventually ruin your kidneys. Kidney stones are also a concern. When your kidneys are stressed from the extra work, it can slow calcium absorption. That can lead to kidney stone production, if you're already prone to the problem, Petre says.
• Risk for constipation. Fiber is important for digestion and regularity. When you replace fiber-rich foods like whole grains, vegetables, fruit and beans with animal proteins that have virtually no fiber, it is nearly impossible to get the recommended 25 to 35 grams of fiber per day. "You will wind up feeling bloated, gassy and constipated," Petre says.
• Risk of developing an eating disorder. The focus on eating such a restricted diet could lead to disordered eating. In other words, you may become so focused on the diet that you develop an unhealthy dependency on your regimen.
• Too much saturated fat. We know now that fat isn't the great nutritional villain we once believed it to be, but we do know that the approach to fat isn't one-size-fits-all. Some people do produce more cholesterol after eating high-fat foods than others, so they may need to eat less saturated fat to manage their risk of cardiovascular disease. This diet may have too many fats for some individuals.
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"A diet this restrictive could be particularly hazardous to persons with eating disorders, pregnant or lactating women, and children or adolescents," Yule says. "People with certain undiagnosed metabolic disorders may also be putting themselves at risk by extreme—and not medically indicated—diets."
Yule sites an example of a case report in which a woman with an undiagnosed urea cycle disorder (a condition that prevents your body from removing waste) died after consuming a diet very high in protein.
Elimination diets are routinely used to help you and your doctor detect food sensitivities, and this diet could be used in that manner. However, it's advised that you work with your doctor to construct an elimination plan that suits your needs and the foods your doctor is looking specifically to test.
Likewise, people who have chronic diseases like diabetes and heart disease are advised to consult with their doctor or a dietitian before beginning this diet. Anyone with any form of kidney disease should also avoid this diet.
The carnivore diet may be successful as short-term weight-loss tool, but you will also give up a lot of freedom in this highly restricted form of eating.
Indeed, many social traditions involve food, from holiday parties to celebratory lunches. Sticking with this diet may be increasingly difficult over the long run, and you may find it's either too tricky to maintain or too isolating.
Without research to support the claims of carnivore diet proponents, it's impossible to say if this diet could be successful in the long run. As with any diet plan, some diets work for some individuals but not for others. And experts urge caution, citing its lack of fiber and other important plant nutrients.
"If a person is trying to cure an underlying medical issue with this diet, I would recommend that they explore all available options with a physician first so that they are better able to make an informed choice," Yule says. "I want to support self-determination by encouraging people to eat in a way that helps them feel better, but at the same time, I am concerned about the potential negative consequences of this diet over the long term."
The smarter, healthier approach to diet, meal planning and weight loss is to find a well-balanced eating style that encompasses healthful foods, including fruits and vegetables, with filling nutrients like protein and fat. This allows you the most freedom in choices, and it gives you greater flexibility to eat foods you enjoy and crave.