The Carnivore Diet: Is It Healthy and What Do You Eat? — Diet Doctor (2024)

Why people turn to carnivory

At Diet Doctor we recommend above-ground vegetables in our low-carb and keto guides and recipes. This suits most people very well because such vegetables are very low in carbs and contain a lot of fibre, nutrients, and trace minerals. They can also be filling.

One can generally eat a few servings of kale, broccoli, cauliflower, Brussels sprouts, zucchini, and other veggies without exceeding 20 grams of net carbs a day. Moreover, eating a mixture ofnon-starchy vegetables with animal products like meat and cheese provides good dietary variety, which can make low-carb eating more interesting and sustainable for the long term.2

Not everyone, however, achieves complete success on a low-carb ketogenic diet that is rich in vegetables. According to comments gleaned from various carnivory websites, Facebook groups, and discussion forums, some people tried a keto diet first but were dissatisfied with their results, prompting the trial of carnivory.

“By and large, most people doing the carnivore diet have some persistent health issue that the keto diet did not completely fix, such as not enough weight loss, a mental health condition, an autoimmune condition, or uncontrolled cravings,” says Dr. Paul Mabry, a zero-carb US family doctor who blogs at Born to Eat Meat and manages a Facebook group, Zero Carb Doc, which now has more than 8,500 members.

Dr. Mabry says he was “a total sugar addict” who at first did well on a keto diet that included lots of vegetables. He lost 50 pounds on keto, but his weight stalled at 230 pounds — which was about 50 pounds above his ideal weight. Plus, his hand eczema, cravings and tendency to overeat continued.

“Even the tiniest amount of carbs can start my cravings and binging,” said Dr. Mabry.

In 2015 he began a carnivore diet, eating almost 80% fat and 20% protein. His weight dropped, his hand rashes cleared, and his cravings stopped. He has now maintained a weight of 180 pounds with no issues.

“I don’t think everyone needs to eat a zero-carb diet. But if you are like me, someone who is severely metabolically damaged from a lifetime of sugar addiction, I think it can help,” he says, calling it a total abstinence approach to carbs.

Australian Jane Jordan, a former nurse, did the keto diet for seven years, with good results. She lost weight, normalized her blood sugar and blood pressure, and eliminated her migraines and IBS.

In spring 2018, when Jordan was diagnosed with early-stage glaucoma, a condition that runs in her family, she found some posts that zero-carb might help her eyesight.3 Recent researchhas suggested that Vitamin B3, known as nicotinamide, may potentially be an effective preventive agent or treatment for glaucoma.4 The foods highest in nicotinamide include meat, poultry and seafood.

“Why not try it? I had nothing to lose,” said Jordan.

After seven months of the carnivore diet, a retest of her eyes by her optometrist in October 2018 found no evidence of the disease. “I am convinced that it was the zero-carb diet that reversed it,” she says.5

There are currently no research trials examining the carnivore diet for glaucoma. But stories of health improvement can even be found as far back as 1799, where a case report was published describing a meat-only diet being used in conjunction with other therapies to “permanently cure” a case of type 2 diabetes (although it would more likely be accurately described as “remission” or “management”).6

Disclaimer:. Stories like these are anecdotes and do not equal good research evidence. We tend to hear more about the positive stories of people on carnivore diets. No research exists about how many achieve health improvements and how many experience negative symptoms or no improvements.

It is clear, however, that success is not guaranteed for all on the diet. Other people in Facebook groups and discussion forums have complained of weight gain, bloating, digestive upset, increased body odor, increased acne, increased tartar on teeth, and other unwanted or lackluster results after adopting a zero-carb diet.7

Popular podcast host Joe Rogan publically commented on his “explosive diarrhea,” but noted this self-resolved after a couple weeks. Non-peer reviewed surveys from Dr. Shawn Baker and Amber O’Hearn report infrequent side effects and mostly beneficial findings.8

Experts weigh in: some pro, some con— some alarmed

Among low-carb experts, the carnivore diet is controversial.

Low-carb neuroscientist Rhonda Patrick, PhD, is concerned about the potential for negative gut microbiome changes and the risk of micronutrient deficiencies. “What is attracting someone to try such a restrictive diet without any published studies or long-term evidence? Why would you do it?” she said in an October 2018 podcast with Joe Rogan. She said the most common reason seems to be trying to influence ongoing autoimmune conditions.

Psychiatrist Dr. Georgia Ede supports a trial of the diet. In her popular Diagnosis Diet blog and in this Diet Doctor video, she explores whether vegetables are truly necessary for health. While there are ample data reporting health benefits from eating vegetables, the question remains if someone can maintain good health long-term while completely avoiding vegetables. She told participants at the 2018 Low-Carb San Diego conference that she was currently trying a carnivore diet herself and, so far, was experiencing positive results, such as improved sleep, steady mood and resolution to her migraines and night-time leg cramps.

Dr. Ted Naiman says he has now had many patients who have done 30-, 60-, and 90-day trials of the carnivore diet, with generally good results and normal labs. However, he has been finding that longer term, the diet may be more concerning. “I’ve now had a small handful of patients who were doing this longer than six months who have reported vague fatigue. The lab workup in these people is usually normal except for very low folate levels, below the normal range.” (Folate, or vitamin B9, is an essential vitamin found in high amounts in green vegetables, egg yolks, organ meats, avocado and legumes. Here is a list of food folate sources.)

Dr. Steve Phinney is concerned about potential deficiencies in sodium, magnesium, and potassium in those who follow the carnivore diet.9

Dr. Jason Fung says, “There is little research evidence around it. But if people are doing well on it, I don’t have a problem with it. And if micronutrients are an issue, you can always take a daily vitamin.”

Other low-carb experts who were approached for their opinion for this story decided to pass: “There are no long-term studies. I’d rather not comment,” was a common response.

Most mainstream dietary experts, who generally don’t support low-carb ketogenic eating, are alarmed. They call the carnivore diet extreme, insane, and a bad idea.

Testimonials, blogs and advocates bloom

Despite the controversy, some high-profile individuals are sharing how a carnivore diet helped resolve their intractable problems, especially mental illness and serious autoimmune conditions.

One of the most prominent and dramatic stories is of Canadian Mikhaila Peterson, who had juvenile rheumatoid arthritis that was so severe she’d had three joint replacements (a hip and two ankles) before age 17. She also had extreme fatigue, anxiety, and depression. In 2015 she began eliminating foods to see if a specific food was contributing to her autoimmune issues. She ended up eating just beef, salt and water — and all her symptoms disappeared.

Peterson’s father is the controversial University of Toronto psychologist Jordan Peterson, PhD, the bestselling author of 12 Rules For Life. Peterson witnessed his daughter’s improvements, adopted the same diet, and has said it caused his long-term depression to lift. Both Mikhaila and Jordan’s stories have been featured on Diet Doctor.

Other high-profile advocates include orthopedic surgeon Dr. Shawn Baker,Kelly Hogan who blogs at My Zero Carb Life, and Esmée La Fleur who runs the ZeroCarbZen website, where she interviews other carnivores about how the diet has impacted their health.

Meat Rx, Dr. Baker’s website, collects hundreds of testimonials of personal health transformations.Just Meat, curated by bitcoin entrepreneur Michael Goldstein, has a large collection of articles, historic documents, archeological studies, and other carnivory links.

Included at ZeroCarbZen are all the archives of the late Owsley Stanley, a.k.a “The Bear”, the former sound engineer (and LSD supplier) to the Grateful Dead. Stanley was a carnivore for some 50 years, and while the rock band happily took his drugs, they would not take his dietary advice. His story is fascinating reading.

Some of the most scientific and nuanced writing on the carnivore diet is being done by Amber O’Hearn, who has a popular blog and website Mostly Fat. A computational mathematician, O’Hearn has been a carnivore for more than a decade and says she will stay on it for life, because it is the only way of eating she has found that controls her bipolar disorder. She speaks at many low-carb conferences, and even hosted her own carnivore conference in 2019. Her full-length podcast is available on the member side of Diet Doctor.

“I don’t advocate eating a carnivore diet for no reason at all,” O’Hearn says. “If you can eat a more varied low-carb diet with good results, why wouldn’t you?” But she also rejects the dominant, unchallenged view that humans simply must eat vegetables for health and that pure carnivory is physiologically implausible.

Available Research on Carnivorous Diets

Although research regarding plant-free diets is scarce, and there are no randomized controlled trials, there are some publications on the topic.10 Amber O’Hearn, for example, published a paper stating that the diet can meet all micronutrient needs, including Vitamin C.11

A case series published in December of 2020 reported five out of six subjects starting a carnivore diet resolved their small intestine bacterial overgrowth (SIBO).12

A paper on the effects of a Paleolithic Ketogenic Diet (PKD) on serum magnesium levels showed normal levels in all but one person, and reports of leg cramping resolving on PKD (which can be triggered by magnesium deficiency).13

Finally, researchers from Harvard University, Dr. Belinda Lennerz and Dr. David Ludwig, published a study from over 2,000 individuals who self-reported their experience with a carnivore diet.14 The results were overwhelmingly positive with 93% improving or resolving obesity or overweight, 93% for hypertension, 98% for diabetes or insulin resistance, 97% for gastrointestinal symptoms, and 96% for psychiatric symptoms. Although the data quality are very low, given the high risk for selection bias with these self-reported outcomes, this study is an important first step toward larger, more rigorous investigations of a plant-free diet.

The Carnivore Diet: Is It Healthy and What Do You Eat? — Diet Doctor (1)

Threads of evidence from our ancient past

So, do we need to eat plenty of plants for good health? What evidence exists that our human ancestors survived, and maybe even thrived, on a largely meat-based diet?

Many of the people listed above draw upon common archeological, anthropological, and physiological sources to argue that humans evolved to be carnivores, and that fatty meat and organ meats are humans’ optimal diet. As hunter-gatherers, they say, people may have eaten plants, tubers, nuts, and seeds when meat was scarce — and gorged on summer fruit and berries to fatten up for winter — but such foods weren’t necessary to maintain health. Meat was.15

Here are some of the key points commonly used to argue that hom*o sapiens evolved to eat a diet mainly of meat and fat.

  • Evolution of human brain size: Over the span of human evolution, the size of the hominin brain has dramatically increased.Some hypothesize that brain size grew every time a more nutrient-dense, energy-rich animal food source was eaten, especially animal fat.16 In short, some declare that animal meat and fat gave us our brains and made us human.
  • Highly acidic stomach: The human stomach is more acidic than other primates. Herbivores and omnivores often have less acidic stomachs, while the inside of the human stomach is so acidic, it is noted as being closer to carrion feeders (meat scavengers) than other carnivores or omnivores.17 This degree of acidity may imply that carrion feeding played a vital role in human development.
  • Evolution of the human gut size: As our brains were growing, the length of our digestive tract was shrinking.18 Herbivores like cows, rabbits, and horses have long, complicated digestive tracts to break down plant cellulose, while carnivores like lions, wolves, and dogs have short, simple digestive tracts. In ominvores like humans, the GI tract is slightly longer than that of carnivores but much shorter and less complex than that of herbivores.
  • Ancient human and animal remains: Anthropologic studies have found evidence of meat-eating among our distant ancestors going back more than 2 million years. Caches of both human and animal bones in ancient caves and burial sites yield important clues. Cut marks and smashed ancient animal bones show probable evidence of butchery and marrow extraction.19Analysis of the ratio of nitrogen and carbon laid down in ancient human and Neanderthal bones can give potential information about the protein source of their diets.20 Studies have found that Neanderthals likely had an almost exclusive diet of large fatty mammals like woolly mammoth. However, as these large game animals, like elephants, became more scarce, early modern humans may have survived because of their ability to eat from more varied sources like freshwater fish and smaller mammals — while still predominantly carnivorous.21
  • Cave art: Bones found in caves are one clue, but what did early modern humans draw in ancient caves such as Spain’s Altamira cave and France’s Chauvet cave? Berry bushes and leafy greens? Nuts and tubers? Nope. Animals! Lots and lots of animals: bison, horse, doe, auroch, wild boar and even (in some cave systems) rhino, mammoths and lions. It is believed these drawings, which are often more than 30,000 years old, were symbolic shamanistic rituals created to increase the success of the hunt, the tribe’s primary and most important food source.
  • Agricultural revolution brings a decline in health: Best-selling author and academic Jared Diamond penned a famous 1987 essay, The Worst Mistake in the History of the Human Race, in which he amasses multiple lines of evidence to conclude that the invention of agriculture “was a catastrophe from which we have never recovered.”22
  • Meat-only study: Jump ahead to the early 20th century when arctic explorer Vilhjalmur Stefansson (1879-1962) did three expeditions in the Canadian arctic, living with the Inuit. For at least seven years he lived on meat alone. Others did not believe such a diet could be healthy, so in 1928 he and an expedition teammate were admitted to a ward of New York’s Bellevue Hospital to be fed a meat-only diet (with plenty of organ meat) for a year and “to be intensively studied on every clinical angle.”23At first the meat served was too lean, making Stefansson sick, but as soon as the fat was upped the pair thrived. A second 1930 paper, based on that year-long study, found no vitamin deficiencies, normal bowel function, improved dental health and that “the subjects were mentally alert, physically active and showed no specific physical changes in any system of the body.”24 In the late 1950s, a few years before his death, Stefansson was interviewed on television about his experiences, which makes fascinating viewing.
  • The teeth of the Inuit: In 1929, around the same time as the Stefansson study, a Harvard dentist studied the teeth of the Inuit.He concluded that “eating a strictly meat diet is the ideal way in which to keep the human mouth in a healthy condition.”25
  • The essential role of Vitamin B3: Found naturally in meat, fish, eggs, cheese, and milk — as well as some plant foods — vitamin B3 is an essential nutrient for the functioning of all our cells and nervous system. Also called nicotinamide or nicotinic acid, its presence in the human diet, some theorize, has played a key role in human evolution, especially in brain and central nervous system development.26A vitamin B3 deficiency, called for centuries by the name pellagra, was a horrible condition known by the four Ds — dermatitis (scaly skin sores), diarrhea, dementia, and death. In 1915 US epidemiologist Joseph Goldbergerfound that it was caused by a diet “poor in animal protein.”27

While none of these factors prove that in our modern age we would be better off limiting ourselves to a carnivore diet, they are key arguments used by carnivore diet proponents that humans evolved to rely heavily on animal-sourced foods.

Paleomedicina in Hungary: treating dire conditions with a zero-carb diet

While an increasing number of doctors are recommending the low-carb ketogenic diet to treat a variety of medical conditions, currently we are aware of only one medical clinic that is using the zero-carb, all animal-sourced diet as a therapy for a wide variety of serious conditions. That clinic is The International Center for Medical Nutritional Intervention (ICMNI) also popularly known as Paleomedicina in Zalaszentgrót, Hungary.

The team, headed by research neuroscientist Dr. Zsófia Clemens and physician Dr. Csaba Tóth, uses its paleo-ketogenic diet therapeutic protocol to treat a wide array of autoimmune conditions, type 1 and type 2 diabetes, mental health conditions, and even cancer.

Developed in 2010-2011, their protocol follows what the clinic believes early modern humans evolved to eat. The diet has a ratio of two parts animal fat to one part animal protein.28 Acceptable protein sources are fatty red meats and organ meats, preferably from pasture-raised animals. No nitrates, nitrites, or additives to meat are allowed. A very small amount of vegetables — mostly leafy greens — are allowed as long as they do not take people out of ketosis, but they are not deemed to be necessary.

On the diet, eggs are at first eliminated but reintroduced after about six weeks to see whether they trigger any negative symptoms (for some, they do). The diet does not allow any dairy products, fruit, sugar, grains, starchy vegetables, or processed carbohydrates.

Since 2013, the clinic has used their paleo-ketogenic diet to treat more than 10,000 patients, according to Dr. Tóth. They’ve published case studies of the reversal of Crohn’s disease, halting of the progression of type 1 diabetes, reversing a precancerous condition, and halting the growth of malignant cancer of the soft palate, the rectum, and the brain.29 Their groundbreaking but controversial work has been featured in a number of podcasts, articles and presentations. Their findings have not yet been reproduced by other researchers or studied in experimental trials.

In an interview with Diet Doctor, Dr. Tóth described how he searched for years to find a way to cure his own health problems: type 2 diabetes, high blood pressure, severe eczema, and severe Crohn’s disease. He first found the paleo diet, which helped his conditions but did not cure them.

It was only when he combined the paleo diet with the ketogenic diet that his health problems resolved.30“Moreover, every clinician in the clinic now eats this way, too,” he says. “We are convinced that this is the healthy way of eating.”

The role of intestinal permeability

Drs. Tóth and Clemens say their experience suggests that a key mechanism of the diet may be its positive impact on the function of the intestine, healing and reversing intestinal permeability, also sometimes called “leaky gut.”

While in the past, mainstream medicine largely dismissed the theory of illnesses being linked to a leaky gut as being pseudo-science, recent research is confirming that a breakdown of the gut barrier can occur.31 Data from a number of academic institutions demonstrate that an increase in intestinal permeability is a common feature of a number of autoimmune and chronic disease conditions.32

A “healthy” intestine absorbs nutrients and energy for use by the body and is more likely to keep out microbes, antigens, and other potential disease-causing agents. The theory is that increased permeability allows unwanted substances to cross the intestinal barrier, triggering inflammation and a dysfunctional immune response.33 “If you have high intestinal permeability, then it is a high probability that all biological membranes are malfunctioning, such as the blood-brain barrier,” said Dr. Tóth.34

All of Paleomedicina patients undergo a test, called PEG400, to measure their level of intestinal permeability before and after starting the diet.35 Dr. Tóth said at Paleomedicina they have shown by repeating the test that their paleo-ketogenic diet can restore the gut wall to normal permeability within a few months.36

What about colon cancer?

Don’t we need to eat vegetables and fibre to prevent colon cancer? Leading health institutions like the World Health Organization and the World Cancer Research Fund declare that red meat causes colorectal cancer and constantly urge us to eat less of it. Wouldn’t a meat-only diet increase the risk of developing cancer?

Diet Doctor has an in-depth guide to red meat and another one on diet and cancer that discuss the weak evidence regarding red meat and cancer, as well as explore whether vegetables are protective. We direct you to those guides for a more detailed evaluation of meat and cancer risk.

N=1: My one-month trial

When Dr. Andreas Eenfeldt asked me to research and write this guide to carnivore eating, it became clear I should give the diet a try myself.

I wasn’t so sure I wanted to. I love vegetables and salad. I have a big vegetable garden; tending it and eating its bounty is a source of joy. Plus, I’ve had no outstanding health complaints since adopting the ketogenic diet in 2015. I’m now happy with my weight; I’ve no auto-immune conditions nor mental health concerns; I’ve no trouble controlling carb cravings.

In short, unlike many who try the carnivore diet, I didn’t have an overwhelming motivation — except this guide — to try this way of eating.

In addition, I was reluctant to tell my family and friends I was eating only meat. It felt extreme. It did not lend itself to dinner parties, lunch dates with girlfriends, and other forms of socializing. I didn’t want to get lectures about the evils of meat or have friends think I’d developed an eating disorder.

So, I embarked on a quiet trial, not telling anyone I was doing it. At first I thought I would just do a week, but I learned that would be too short to demonstrate anything.

“It takes about 30 days to see appreciable differences from this diet and often longer, compared to a merely ketogenic one,” advises O’Hearn.

Calmer gut, lower body fat, more hot flashes

First, here is how I ate:
  • I either had eggs and bacon for breakfast or skipped breakfast completely. I did have a cup of coffee with full-fat cream every morning.
  • For lunch I would often cook ground beef with butter and salt, sprinkled with a bit of grated cheddar cheese. If I hadn’t had breakfast, I might instead have two eggs for lunch, or an omelette with cheddar cheese. Sparkling water was my go-to drink all day.
  • For dinner, it would usually be a piece of meat — steak, rib eye, pork chop, sausage, lamb chop, liver — with a tiny bit of fresh kale or lettuce from my garden (such as is allowed on the Paleomedicina protocol). It was not enough greens to call it a salad — and it had no dressing — but was just a bit of color so my plate did not look so bare. I honestly found it hard to see a plate with just meat on it. Seeing the green and chewing a few sprigs of kale or parsley with the meat felt refreshing. I called it my palate cleanser.
  • I did not snack at other times of the day. Already being keto-adapted helped with this. I don’t believe I could have eaten this way if I had not already been on a low-carb, keto diet for three years.
The results:
  • GI tract: The first four days I had significant digestive upset — mostly diarrhea hitting in the middle of the night. Not nice. But then my gut settled down and was remarkably calm for the next 30 days.
  • Weight: I lost 5 pounds within two weeks and kept it off for the 30 days. In three years of ketogenic eating my weight had become very stable. I thought it was as low as I could realistically go as a 60-year-old woman. It was not. Within a month of stopping eating carnivore, however, I had gained 4 pounds back.
  • Body fat: My body fat percentage, which had come down from 36% to 29% on the keto diet, came down even more to 26.5%. My exercise routine stayed the same.
  • Fasting blood glucose: My fasting blood glucose was 85-86 mg/dl (4.7 or 4.8 mmol/L) every morning — optimal.
  • Ketones: My daily ketone levels were not as high — usually about 0.3 to 0.7 mmol/L. When I ate a low-carb ketogenic diet my ketones would typically be 1.5 to 2.0 mmol/L.
  • Hot flashes: I would get extremely hot, especially after my evening meal and in the middle of the night. At first I thought it was a return of menopausal hot flashes, but then in a Facebook discussion among others with the same reaction, it dawned that it might be protein thermogenesis — the meat sweats — from the digestion of protein. At times I was uncomfortably hot. It made me think maybe this internal, meat-driven furnace was how our paleolithic ancestors survived in winter climes wearing just animal hides and tree bark.
  • Better skin: Some long-standing sun damage (keratoses) on my legs and shoulders simply disappeared. Weird.
  • Brain: I did not notice any difference in mood, mental acuity, or mental energy between keto and carnivore. If anything, I think I feel mentally happier eating vegetables. It may have been because I was not outside tending and using the produce from my garden during the month and was not socializing with others over meals.
  • Cravings increased: On the low-carb keto diet I’ve generally had no cravings. On carnivore my cravings actually increased — substantially. I especially longed for fresh salad, raw and steamed broccoli, fresh fruit and berries — and even bread and popcorn. I craved sweets, too. At a party during the month, I could not resist the dessert table, which hadn’t occurred in the past on the keto diet. I think I wanted a different mouthfeel, a different taste, even for just a moment. I am not sure what was happening with me but I found the cravings tough.
  • Monotony: I definitely felt deprived of flavours and textures, and as time went on I was just less interested in eating meat. It was very easy to skip a meal because at times I simply didn’t hanker for any more flesh. But, on the other hand, shopping was simple and meal prep and clean up was super fast.

The biggest surprises to me were how it nudged my stalled weight a few pounds, the calm gut and the improved skin. The most difficult was the tedium, the surges of body heat, the cravings, and my self-imposed feeling of social isolation from the diet.

I thought often of Amber O’Hearn’s comment, “If you can eat a more varied low-carb diet with good results, why wouldn’t you?”

That described me to a T (make that a T-bone!). I didn’t really need to do the diet, so the trade-offs were high. I had no concerning health reason to motivate me; it felt restrictive and limiting. I did not eat out with friends for a whole month. I was glad when my trial was over.

I’m now back to eating a low-carb ketogenic diet with plenty of above-ground vegetables. I am happier making many of the delicious Diet Doctor recipes. That way of eating feels more enjoyable, balanced, and sustainable to me.

That said, however, I understand better why those with severe or incurable conditions with poor therapeutic options might try carnivore eating. In the absence of any good scientific evidence pro or con, doing their own n=1 trial over a few months might determine if they are likely to experience any benefit.

Short term, it is unlikely that it would do any harm. But as Dr. Naiman notes above, longer periods of zero-carb eating might cause health issues for some people. So it is important that anyone considering a trial should pay close attention to their individual responses. If there’s no improvement over weeks or a few months, it’s likely not helping, and people can feel satisfied returning to a more varied and less restrictive low-carb or ketogenic diet.

/ Anne Mullens

The Carnivore Diet: Is It Healthy and What Do You Eat? — Diet Doctor (2024)


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