The latest fad diet sweeping the internet is the carnivore diet (also known as the zero carb diet). The idea is that by cutting out all plants and only eating meat you’ll quickly lose fat, control your appetite, improve strength and vitality, and actually cure many chronic illnesses. I call it a fad because it has all the classic signs of a fad diet:
- Promises fast fat loss,
- Promises to control appetite so it feels easier,
- Promises to improve health so you’ll feel better,
- Has no or limited scientific evidence to back claims,
- Yet has many anecdotal stories of success,
- But ultimately even the biggest proponents have no idea what the long-term health consequences are.
That last point is my biggest problem with the carnivore diet. There are all kinds of unhealthy ways to burn off body fat. Some cause short-term damage, while others inflict lasting harm. Other diets (like low-carb diets), which were once thought of as fads, eventually proved their safety and effectiveness and became legitimate dietary practices. The question is which is the carnivore diet, a dangerous fad or a pioneering breakthrough?
I’ll go over why the carnivore diet works, my concerns about it’s long-term safety, and what you can do to minimize those potential unknown harms.
Why it works
Fans of the carnivore diet tout that it causes rapid and sustained fat loss without the need to count calories. This isn’t surprising at all. If you’ve read my guide on how to structure a successful diet, you’ll know that it’s all about limiting the amount of carbohydrates you eat and the speed at which your body absorbs them. Carbohydrates are hard to store and actually harmful if left to circulate in your system too long, so your body always wants to use them up first.
Your body releases insulin to shuttle blood sugar into muscles. To make sure the sugar gets used up first, insulin also tells your fat cells to store any fat you consume and to not release stored body fat for hours afterwards. If you eat a lot of easily-absorbed carbohydrates, your body releases a ton of insulin in response. Excess insulin can then remove too much sugar from your blood stream, resulting in hypoglycemia. The quickest way to restore blood sugar levels is to eat more carbs, which puts people on the carb roller coaster to weight gain.
Cutting all carbohydrates out of your diet removes a major fat-storing signal from the equation. On top of that, protein has been shown to have additional appetite suppressing effects.
One way that protein controls appetite is through the amino acid phenylalanine. Consumed protein is broken down into amino acids so it can be absorbed by the body. Multiple studies have shown how phenylalanine suppresses appetite and even improves mood and helps you burn stored fat. One study found that phenylalanine increases the release of an intestinal hormone called cholecystokinin in humans. This hormone signals the brain to feel satiated after eating and causes a reduction in subsequent food intake. A mouse study found that a single dose of phenylalanine caused an increase in another satiety hormone called GLP-1, it reduced levels of the hunger-hormone ghrelin, and it caused the mice to move around more. One of the reasons it caused them to move more is because phenylalanine is a precursor for norepinephrine and dopamine.
The purpose of norepinephrine is to rouse your body for activity. It increases your focus, delivers blood to working muscles, and mobilizes glucose and stored fat to fuel your movements. Dopamine is considered the reward-hormone and increasing it’s levels in your brain is helpful for making your weight loss diet less unpleasant. Eating is a pleasurable experience and the dopamine decreases that typically come from a diet can cause people to quickly abandon their plan and return to a poor diet to get that good feeling back.
Another benefit that I’ve gathered from the anecdotal success stories is that the carnivore diet tends to make people naturally adopt time-restricted eating patterns. Studies show that eating at night is a common cause of obesity. In fact, studies have shown how junk food actually causes you to prefer late-night eating. Sugar and fat together acts as a trigger that cements the unhealthy habit of late-night eating. Worse yet, your body runs on an internal clock called circadian rhythms. These do more than set your sleep and wake times, they also determine your digestion and energy usage times. We’re meant to eat during the day and sleep at night. When you eat at night, your body doesn’t want to process those calories and instead they sit and cause metabolic dysfunction.
Protein does not seem to trigger a desire for late-night eating so the carnivore diet also helps curb that unhealthy practice. Late-night eating also reduces the quality of your sleep and poor sleep leads to poor eating the next day. Reduced sleep also increases stress and anxiety, so removing late-night eating not only improves weight loss, but helps your mood and overall feeling of well-being.
So the carnivore diet does have some immediate and noticeable benefits, but where they start to lose me is when they explain how we were never meant to eat plants of any kind. Ironically, vegans use the same argument when they explain that we were never meant to eat meat. They give some overly-simplified analogies about the shape of our digestive system compared to other animals and explain that it’s eating this one category of food that’s causing ALL chronic illnesses. Notice I didn’t say which “they” it is because both vegans and carnivores say the same thing; cut out that “other” awful category of food and you’ll instantly feel better. Well, they are both right about the fact that you’ll feel better, they’re just both wrong on what actually caused problems in the first place.
Cutting out processed food makes you feel better
Every study that wants to examine the effects of the worst diet possible uses what’s known as the Western Diet or the aptly named SAD (Standard American Diet). It’s characterized by processed foods high in fat, sugar, and salt (to trigger appetite) and low in fiber. Red meat also gets lumped into the Western Diet which is why it’s always demonized as a cause of chronic illnesses. I’ve already written about why I think that’s an unfair categorization, and you can read more about it here if you want.
One of the big reasons why everyone feels better when they adopt any kind of extreme diet, whether it’s carnivore, vegan, or one of a million structured plans, is because they’ve stopped damaging themselves with the Standard American Diet. Calorie-dense, low-quality processed foods cause rampant systematic inflammation that damages every cell in your body and shortens your life. Chronic inflammation is the cause of poor aging. It increases pain and dysfunction, and it leads to all kinds of diseases that we associate with aging like arthritis, heart disease and cancer. As I mentioned above, the SAD junk food diet also disturbs your sleep patterns which makes you feeling stressed out and lousy the next day. No matter my concerns about the carnivore diet, I can confidently say it’s far safer than the Standard American Diet.
My carnivore concerns
While I do agree that cutting excess body fat is important to improve your health and longevity, you don’t want to sacrifice your longevity to accomplish it. We have all kinds of adaptive and protective systems to defend us against our environment, but they need certain nutrients to function. First I want to go over potential dangers to be aware of with the carnivore diet and then I’ll address ways to limit the damage if you do chose to try it yourself.
IGF-1 trade off. The reason why the carnivore diet seems to reduce inflammation and improves strength and vitality is because eating meat increases IGF-1 (insulin-like growth factor-1) levels. While IGF-1 does provide nice benefits, there is a trade off.
When I first started reading studies about red meat causing cancer, they were all epidemiological studies that concluded red meat was the cause of illnesses like cancer even though they always threw in a rather important line deep in the study saying that “people that ate red meat also tended to smoke more, drink more, exercise the least, and eat low amounts of fruits and vegetables.” Each of these alone is a far greater risk factor, and grouping them together as incidental factors is flat out fraud. It’s my prime example concerning epidemiological studies and researcher bias. The researchers wanted red meat to be the cause before they even began looking at associations, so to make their conclusions work, they simply ignored everything else.
However, there is a legitimate issue with red meat (or an all-meat diet) that the more honest researchers have pointed out. Red meat raises IGF-1 levels and if you’ve already suffered DNA damage, this growth factor can help precancerous cells proliferate. Cancers like colorectal cancer, prostate cancer, meningioma, glioblastoma, and pre-menopausal breast cancer flourish in the presence of IGF-1. This doesn’t mean that it causes these cancers, but high levels of IGF-1 can help them take off.
There is also a link between low IGF-1 levels and longer lifespans. It’s been shown in animals that decreasing IGF-1 levels increases overall lifespan and centenarians (people living past 100) tend to have a polymorphism that causes decreased IGF-1 levels. It’s also one of the reasons why calorie-restricted diets show increased lifespans in animals and possibly humans.
The problem is that IGF-1 also offers a host of benefits. It’s a growth factor after all. It helps build and repair muscles and bones, triggers neurogenesis in the brain and protects against dementia, and has antioxidant and anti-inflammatory properties. In general, it helps you feel stronger and more vital as you age. Those centenarians with low lifetime IGF-1 levels also tend to be smaller and more frail. It’s the IGF-1 trade off that you’ll see on many sports and nutrition sites. High IGF-1 levels improve overall performance but the trade-off is it could lead to a shortened lifespan.
IGF-1 shuts down autophagy. As I mentioned above, IGF-1 doesn’t cause cells to turn cancerous, but it can help caner cells grow and proliferate. IGF-1 also prevents your body from cleaning up damaged cells before they can become cancerous. We incur cellular damage all the time. Some of it comes from external sources like solar radiation, pollution, and infectious bacteria and viruses, but chronic inflammation from your own immune system can also damage DNA.
When a cell incurs too much DNA damage, it loses the ability to divide and becomes senescent. This is actually a vital part of healing and an important defense mechanism against excessive stress. If a cell with damaged DNA was able to divide, it could allow dangerous mutations to spread throughout your system and lead to cancer. When a cell becomes senescent, it not only stops replicating, but it sends out dozens of signaling molecules to alert your body that this damaged cell should be recycled through autophagy and replaced. Senescent cells release pro-inflammatory cytokines and prostaglandins to attract immune cells and kill the damaged cell. They also release growth factors and proteases to aid the surrounding cells and help them replace the senescent one. It’s an important part of wound healing and regeneration, but if your body doesn’t activate autophagy, then those damaged cells sit there pumping out harmful inflammatory signals that damage nearby cells, and all those growth factors that are released to help replace the damaged cell instead help it turn into a proliferating cancer cell.
mTOR (mechanistic target of rapamycin) is an important enzyme that regulates things like cell growth, cell survival, protein synthesis, and autophagy. It also promotes the activation of insulin and IGF-1 receptors. This is why the presence of IGF-1 and insulin increases the amount of mTOR. You need to down-regulate mTOR in order to trigger autophagy. As an additional benefit, decreasing mTOR also causes senescent cells to down-regulate the release of inflammatory secretions. This means even if you don’t kill those cells through autophagy, you at least stop them from inflicting damage to the surrounding cells for months afterwards. IGF-1 has a pretty high half life in your body (about 12 hours) so if you want to keep autophagy running at all on a carnivore diet, you’ll also want to practice intermittent fasting.
Ignores the microbiome. There are a handful of discoveries in recent years that have truly revolutionized our understanding of nutrition, health, and longevity. The concepts of intermittent fasting for autophagy and time-restricted eating are two that you will see more and more health professionals recommend over the coming decades, but one of the biggest discoveries is the importance of the microbiome for proper health and function.
One of the hallmarks of the terrible Western diet is a near absence of fiber. We’ve always seen in epidemiological comparisons that people that ate more fiber tended to have better overall health but we never knew why. It turns out the good bacteria in your colon consume the fiber that you can’t digest and then release all manner of metabolites, signal molecules, and neurotransmitters that you need in order to develop properly and function. They also act as the first line of defense for your immune system. You can wash or cook food as much as you want, but you can never sterilize it. The good bacteria in your microbiome work as a part of your immune system to prevent these invaders from proliferating and causing you harm.
When these good bacteria don’t get the fiber they need, they die off and you lose any benefits they would have provided. The loss of bacterial species is known as dysbiosis. Since the microbiome plays a large role in regulating your immune response, the elimination of many of these species has caused a significant rise in all kinds of auto-immune diseases as well as cancers, mental disorders, and obesity. Your microbiome is a complex system where different strains live off of the metabolites released from other strains. We can’t even study the majority of them outside of the body because we don’t understand which combination of metabolites keeps them alive. The understanding of how it all works is in its infancy, but all researchers agree on one point, people and animals with a more diverse range of microorganisms tend to be healthier.
One of the best ways to reduce the diversity of your microbiome is by cutting out all fiber. Ironically, a lot of people espouse the carnivore diet to help control auto-immune diseases. I understand why this would work. If you have an imbalanced microbiome, feeding fiber to those overgrown bacteria will only strengthen that imbalance and increase symptoms. But in the long-term, these imbalances will only become more pronounced if you completely remove fiber from your diet.
Changing your microbiome to one that primarily processes proteins and fats is also harmful. Fermentation of amino acids for energy in the microbiome can produce harmful metabolites like phenols, amines, and hydrogen sulfide which have been shown to contribute to irritable bowel syndrome, colon cancer, increased intestinal permeability, inflammation, and DNA damage. Fermentation of read meat in particular creates additional harmful metabolites like trimethylamine-N-oxide (TMAO) which contributes to atherosclerosis. Studies have found that eating resistant starches alongside proteins keep these harmful metabolites from forming. Eliminating all fiber from your diet increases the likelihood of unnecessary harm. It’s fine in the short-term, but in the long-term, you’ll discover why there is such a strong association between red meat and colon cancer.
Fans of the carnivore diet either claim we don’t know enough about the microbiome to know if it’s harmful (which is true) or make claims like Ryan Munsey who says he had his microbiome tested and found that “At the 1 month mark, my stool showed ZERO dysbiotic flaura in my digestive system and a very favorable array of beneficial bacteria, that have many health-protecting effects in the GI tract including manufacturing vitamins, fermenting fibers, digesting proteins and carbohydrates, and propagating anti-tumor and anti-inflammatory factors.” I’m not really sure what a dysbiotic species is. Dysbiosis just means imbalance. Ryan may only have “good” species of bacteria, but he could have lost dozens of other helpful species in the process. We know certain species are more associated with poor health outcomes than others, but newer studies show that even “bad” bacteria may have a positive purpose.
Most mouse microbiome studies like to start from a “clean slate” so to speak. They either use antibiotics to knock out the current microbiome are they start with germ-free mice that were raised in a completely sterile environment so that they’ve never had a microbiome. An interesting mouse study wanted to test our old assumptions by seeing if previous results are matched when the test mice don’t have a compromised microbiome.
In one experiment, they transplanted the dysbiotic microbiome from obese mice to healthy mice and observed what happened with glucose release from the liver while on a high-fat diet. Normally a high-fat diet triggers the liver to release too much glucose, which then leads to metabolic disease. When the dysbiotic microbiome was transplanted into the non-compromised microbiome of the healthy mice, these “harmful” bacteria instead protected the liver from releasing too much glucose. Another similar test injected a different strain from obese mice into healthy mice and it actually protected the lean mice from weight gain when they were switched to a high-fat diet. The researchers concluded that these species that are associated with metabolic disease and obesity may instead be proliferating as a protective response against unhealthy dietary changes. As the defenders of the carnivore diet point out, our understanding of the microbiome is in it’s infancy and we’re learning more each day. Maybe I’m wrong and a complete lack of fiber doesn’t lead to poor health outcomes. Maybe the changes to the microbiome during an all meat diet will only be temporary and your microbiome can successfully rebound to a health mix after you’re done. There are still three reasons why I think completely removing fiber will be harmful:
1. People in Blue Zones aren’t carnivorous. Blue Zones are regions of the world were people live much longer than average. They all seem to share 9 common characteristics such as strong family connections, strong social connections, moderate wine consumption, they felt the had purpose in life, had relatively low stress, and the tended to have a higher percentage of plants in their diets. Fiber isn’t the main reason for a longer, happier life, but tends to be a common factor in people that do age well.
2. No one anywhere is truly carnivorous. As much as carnivore diet fans like to point to people like the Inuits and Maasai as meat only societies, they both tend to sneak some plants in. The Inuits made tea from pine needles that was high in vitamin C and polyphenols and they ate berries, seaweed, algae, and lichens. The traditional Maasai diet consisted of raw meat, raw milk, and raw blood from cattle but they still consumed some vegetables and fruits and made soups from acacia nilotica. The Maasai also eat soups made from bitter bark and roots containing saponins, and those Maasai who don’t have access to the bitter plants tend to develop heart disease.
3. Good bacteria eat you in the absence of fiber. As I’ve said in a previous article, bacteria aren’t good or bad, they’re selfish. If you provide them food and the right environment to live, they will help you stay alive and work to fight off competitive “bad” bacteria so they can survive and proliferate. One of the main ways beneficial bacteria help you out is by digesting fiber and releasing short chain fatty acids. Your intestinal cells then use this fuel to create a layer of protective mucin. This seals the colon wall and keeps any and all bacteria from entering your bloodstream. When you don’t live up to your end of the bargain by feeding them the fiber they need, they instead eat the mucin barricade and increase the permeability of your intestinal wall. As the intestinal wall becomes more permeable, your immune system detects all the bacteria in your colon (both good and bad) and increases your inflammatory response. This not only kills bacteria from your own microbiome, but it damages tissues throughout your entire body. Worse yet, these bacteria don’t go down without a fight. The outer membranes of many types of bacteria, even the “good” ones contain molecules called lipopolysaccharides (LPS) or endotoxins. They can selectively release these molecules to harm other organisms, but they also release them when killed. These tiny endotoxins are what cross through your weakened intestinal wall and increase damage and inflammation throughout your body.
Ignores micronutrients. Carnivore diet advocates say that you can get everything you need from meat and organ meat like liver, it’s more easily digested (more bio-available) so you need less of it, and certain vitamins and nutrients are really only necessary to help with the metabolism of sugar (like manganese). All of this is true but it’s difficult to meet your daily requirements of certain nutrients on just meat. Unfortunately, to maintain the dogma that meat-only is the right way to eat and all you need is meat, they also say that dietary supplements are totally unnecessary.
Vegans also like to say that you can get everything you need from just plants, but at least they’ll admit it’s OK to take supplements for vitamin B12 and any other nutrients you may be falling short on.
75 percent of Americans are vitamin D deficient and over half the country already don’t get enough magnesium each day, but no one really pays attention to these statistics since they don’t feel any symptoms. Severe vitamin deficiencies will cause symptoms (like scurvy), but in our modern world of over-abundance, no one is ever going to be completely deficient. Even crappy processed foods throw in some vitamins to make their labels appear a little healthier. Since most people feel fine, they just assume they’re either getting enough of what they need each day or all this talk of vitamins must not be important after all. The problem is that our bodies have evolved a simple trick to keep us going strong when our supply of vitamins is inadequate. Unfortunately, it does this by sacrificing your long-term health to ensure your short-term survival.
Think of micro and macro nutrients as your body’s currency. If you have plenty of money on hand, you can take care of all your day-to-day needs and still have a little extra that you can put aside for your retirement. However, when money is tight, you need to prioritize making the rent next month or buying groceries today, and the concept of retirement planning never even comes to mind. This is the basic concept behind the Triage Theory of nutrition.
Your body uses micronutrients like magnesium and vitamin K as cofactors to activate certain enzymes so they can serve their biological functions. When the supply of micronutrients is plentiful, all the enzymes can be activated, but when the supply is limited, your body prioritizes the ones it needs today (like ones that help with blood clotting and reproduction) and ignores the ones that stave off aging, decline, and chronic illnesses (like ones that repair damaged DNA to prevent cancer, the ones that prevent telomere shortening to lengthen your lifespan, or the ones that prevent calcium from hardening your arteries and causing cardiovascular disease).
In sticking with the saving for retirement analogy, the little bit of money you put aside today can eventually grow into a pretty healthy nest egg due to compound interest. Unfortunately, this also holds true with the tiny amounts of damage your body ignores each day in favor of focusing on short-term concerns. We tend to believe things like cancer, heart disease, dementia and other scary illnesses associated with aging are beyond our control. We chalk it up to bad luck or bad genes, but it’s actually a lifetime of tiny damage that your body was unable to deal with. I know that also sounds like it’s out of your control, but it’s actually the opposite. With enough micronutrients, your body can deal with the problems of today and still repair any damage that might hurt you tomorrow.
DNA suffers damage all the time. Ultraviolet light, viruses, exposure to man-made chemicals and plant toxins, and simple errors during replication can cause 10,000 to 1 million molecular lesions per cell per day. This may sound like a lot, but it’s still a tiny percentage of the 3 billion base pairs found in every strand of DNA. Breaks that aren’t repaired before replication can lead to cell death, senescence, and mutations. Over time, the damage that missed out being repaired gets passed along through replication. This compounding of damage can add up to all kinds of disfunction and disease. It’s why we treat the symptoms of age-related diseases rather than hoping to cure them. The time to cure them passed decades ago.
Fine to try
I think overall the carnivore diet is fine to try on a temporary basis. Having extra body fat is also a risk factor for many of the diseases mentioned above and a cause of chronic inflammation. Successfully cutting fat is an important step towards improving your health and extending your life. I wouldn’t suggest adopting the carnivore diet as a long-term strategy. It also does seem to help people with auto-immune problems and digestive issues (at least anecdotally), so it can be used as sort of an elimination diet to test and see what additional foods cause you problems. If you are going to do a full carnivore diet, I have a few recommendations to hopefully limit any possible side effects.
Limiting carnivore issues
Take magnesium. Magnesium is an important cofactor for over 300 different enzymes in the body, including ones responsible for DNA replication and repair, RNA synthesis, and mitochondrial repair and biogenesis. Plus magnesium has been shown to lessen symptoms of depression and anxiety. Magnesium is at the center of the chlorophyll molecule so while it’s easy to get from leafy greens, it’s hard to find in animal sources. Fatty fish like salmon has a lot more than red meat, but I would recommend taking a magnesium supplement like magnesium citrate to be sure. I recommend that to people in general to make sure their body doesn’t sacrifice tomorrow in order to fulfill the needs of today.
Lift weights. If you’re going to increase your IGF-1 levels you might as well use them. Strength training actually reduces serum IGF-1 levels by driving it into the working muscles. Increased IGF-1 will help with athletic performance, but as I mentioned above, the trade off of high IGF-1 is a shortened lifespan. Exercise to reduce circulating IGF-1 levels and limit the longevity vs vitality trade off as much as possible.
Only eat 8 to 10 hours a day. High IGF-1 also raises mTOR which stops your body from clearing out damaged and dangerous cells through autophagy. Try to keep your eating window small to hopefully activate autophagy.
Don’t grill and cook at lower temperatures. As I mentioned in another article, cooking meat at higher temperatures can produce harmful compounds. Normally I would recommend cruciferous vegetables to counter the effect, but since that’s off the menu, you’ll need to reduce the temperature to reduce the harm.
Eat fish. It seems like most carnivore dieters focus on red meat but no one said fish is off the menu. Omega-3 fatty acids are vital for your brain, plus they are also anti-inflammatory. Fatty fish also tend to be a better magnesium source than red meat.
Eat liver or take a multivitamin Liver is basically the carnivores answer to, “How do I get all my micronutrients?” You can either eat liver for your daily dose of choline, folate, vitamin A, vitamin B12, copper, riboflavin, iron, and a small amount of vitamin C. Or you can just take a cheap multivitamin and don’t tell anyone you broke the sacred carnivore code.
Come off the diet like you came off antibiotics. The big complaint with the carnivore diet seems to be that adding fiber back in causes discomfort, bloating, and digestive issues. That’s because you’ve just radically altered your microbiome and it’s going to take 5 to 10 days for it to change back. Think of it like taking an antibiotic. You’ll need a healthy mix of probiotics (including exercise and time spent outdoors) to establish colonies of beneficial bacteria, and a steady supply of prebiotic foods to help them flourish.