The Carnivore Diet
Updated: Aug 23
A couple of weeks back I did a post on veganism and this week we went 180 and dived into the carnivore diet. Even as a vegan I went in and tried my best to find some solid data to back up claims made by those vocal in the carnivore diet "community". Just because you don't agree with something doesn't mean you should be totally biased. I actually found some studies in support of the diet and on initial inspection they looked bombproof. On the podcast, Tom quickly dismantled them and so have many other experts in the field. If you'd prefer a more "entertaining" format on this topic then listen to the full podcast episode down below. For written information continue on!
The way we approached this topic was to look at some of the popular claims made by those who are on the diet and look at if the studies support them.
What is the carnivore diet?
The carnivore diet is a highly restrictive meat-based diet. You essentially cut out all plant foods including oils, sugars, seasonings, sauces, alcoholic beverages, teas and coffee. The primary focus is on fatty cuts of meat with the main focus on beef.
Go to foods and drinks include:
Organs such as liver
Technically some dairy is allowed however things with lactose (milk) contain sugar so It's generally not included.
With any diet, it's best to do what works for you and is sustainable. From what I read online many carnivores will try without tea and coffee but normally include it back into the diet. So not "carnivore purists" but doing the main bulk of it. People will pick and choose and that's fine but you'll always get the hardcore sections of diets who will look down on anyone not doing it 100% by the book.
Go on the carnivore diet to shed the pounds! Let's not mess around. There is absolutely no decent evidence to suggest that if you are on a consistent calorie deficit you will not lose fat/weight in good amounts. This applies vice versa as well. It's also crucial we differentiate between fat loss and weight loss. Our weight will always fluctuate. Simple things like going to the toilet will cause you to "lose" weight. This is not the same as losing fat. To lose fat you have to be in a consistent calorie deficit (burning more calories than consuming) and this is no different on the carnivore diet. If you want to lose fat that is how it's achieved. However, where the carnivore diet receives a lot of good "reviews" online is where in that initial period of going on the carnivore diet you may lose a large amount of "weight". Notice how I used weight there? When you go onto a new diet and the goal is to lose weight you are normally put straight into a calorie deficit and during this initial period you're body turns to glycogen for energy. For every gram of glycogen 4 grams of water is stored. So as you can imagine when you are using this glycogen energy initially you are losing a substantial amount of water weight.
Now, specifically for the carnivore diet, you are cutting out all carbohydrates. When we consume carbohydrates our body converts them into glucose and this becomes an energy source. When the body doesn't need this energy it stores the glucose in the liver and muscles and this form of glucose is called glycogen. Remember what I said about 1 gram of glycogen is 4 grams of water stored. So, on the carnivore diet, we are essentially depleted of glycogen so in those initial couple of weeks you are going to lose a lot of weight simply in water. This is where the abundance of "anecdotal" evidence online comes from. People will go on this diet and because they have lost a lot of weight very quickly they assume this is due to the carnivore diet. Technically yes it is but this is because you have cut out an entire macronutrient. After a few weeks, you will plateau and unless you are in a calorie deficit you will not lose any fat. This is where it's crucial you understand that anecdotal evidence is the lowest form of evidence. If you stumbled across a forum and saw some of the things, people were saying "rapid weight loss on carnivore diet" you may be enticed. This is why posts like these are vital to ensure people are educated on the actual science behind why certain things are happening.
Insulin spikes! This one is total nonsense. They claim that due to insulin spikes from carbohydrates you are inhibiting your ability to burn fat. Le'ts look at the science.
Insulin inhibits lipolysis. Fewer fatty acids are available to fuel muscles and other metabolically active tissues. So insulin spikes = turn off the ability to burn fat?
Insulin stimulates lipogenesis. "Fat storage mode" Lipogenesis can cause carbohydrates to be converted and stored as fat "de Novo lipogenesis" NOTE: De Novo lipogenesis only happens in meaningful amounts when in a constant carb/calorie surplus. What that essentially means is that insulin spikes are not making you store large amounts of fat it's the fact you are consuming too much for your activity levels and are now in a calorie surplus. Now, lipogenesis isn't a free-roaming fat churning machine it's actually partly inhibited by growth hormone & leptin and also in certain foods we eat. Polyunsaturated fats actually inhibit this process as well. Regardless of all this word salad, the bottom line is as I said earlier no evidence to support that you will get fat unless you are in a constant calorie surplus.
But high insulin makes you hungry and in turn eat more? Well for a start insulin isn't solely responsible for hunger levels.
Leptin (helps regulate energy balance by inhibiting hunger)
CCK (Cholecystokinin is a gut hormone released after a meal, which helps digestion and reduces appetite.)
Ghrelin (increases appetite and stimulates the release of growth hormone)
Amylin (plays a role in glycemic regulation by slowing gastric emptying and promoting satiety, thereby preventing post-prandial spikes in blood glucose levels)
GLP-1 ( stimulates insulin secretion and inhibits glucagon secretion, thereby lowering blood sugar)
To further show the limited impact of insulin and hunger I found a small scale study that suggests those on a high carb low-fat diet and those on a high-fat low carb diet don't notice a huge difference in satisfaction/hunger levels.
"The scientists randomly assigned 20 overfat participants (11 men and 9 women) to one diet for two weeks and then had them switch to the other for two weeks.
For each diet, participants were given three meals plus snacks per day, carefully prepared to provide twice the number of calories each individual required. The dieters were then told to eat as much or as little as they desired.
What the study found
► People ate 544 fewer daily calories on the plant-based low-fat diet than they did on the animal-based low-carb diet. (This data is only from the second week of each diet, to allow participants time to adapt. For both weeks combined, the difference was even greater: 689 fewer daily calories.)
► Energy expenditure was 166 Calories per day higher on the animal-based low-carb diet compared to the plant-based low-fat diet.
► Glucose and insulin levels were substantially lower during the animal-based low-carb diet.
► Participants rated both diets the same in terms of pleasantness and familiarity. So one wasn’t deemed more palatable than the other.
► They also reported no differences in satisfaction, fullness, or eating capacity, even though they ate significantly fewer calories on the plant-based low-fat diet.
► Both groups lost weight without intentionally restricting food intake: 3.9 pounds during the animal-based low-carb diet; 2.4 pounds during the plant-based low-fat diet.
► Only the plant-based low-fat diet (1.3 pounds) resulted in a significant reduction of body fat. The animal-based low-carb diet showed a significant decrease (3.5 pounds) in fat-free mass, most likely from water and glycogen, but this measurement also includes muscle, bones, and organs."
Hall, Kevin D., Juen Guo, Amber B. Courville, James Boring, Robert Brychta, Kong Y. Chen, Valerie Darcey, et al. 2020. “A Plant-based, Low-fat Diet Decreases Ad Libitum Energy Intake Compared to an Animal-based, Ketogenic Diet: An Inpatient Randomized Controlled Trial.” NutriXiv. May 6. doi:10.31232/osf.io/rdjfb.
I want to reiterate the point that the study has also identified. The difference between weight loss and fat loss. The high-fat low carb diet reported greater weight loss but lower fat loss for the reasons we discussed earlier and they are also mentioned at the end of the quote above. The key point to mentioning the study above is that although the low carb diet has substantially lower insulin levels both groups reported no difference in satisfaction or hunger.
Better Heart Health?
On a carnivore diet, you are consuming large amounts of saturated fat so you may be thinking how can this lead to better heart health. Well, in the podcast episode I actually brought up 3 whopping studies that showed no clear link between saturated fat and CHD & CVD. At first glance, you'd assume that these studies were fantastic and that everything you knew about saturated fat was wrong. As we've mentioned before, meta-analysis studies are really good. They take a large pool of individual studies and come to a conclusion from there. So essentially using multiple sources of evidence to come to a better conclusion. HOWEVER, what if all these individual studies contain flaws? That would suggest the entire meta-analysis is flawed.
Alan Flannigan the nutritional advocate wrote a great article which basically addressed all these studies. Here is a snippet and then I'll link the full article below.
This issue of the replacement nutrient and levels of saturated fat in the diet is critical to understanding why several recent meta-analyses all purported to find no association between saturated fat and CVD. In the 2010 meta-analysis which began the controversy, the conclusion that there was no significant association was based on analysis of prospective cohort studies, but the meta-analysis failed to consider the replacement nutrient for saturated fat . A further meta-analysis by the same research group comparing saturated fat to carbohydrate also failed to distinguish between the type – whole grain or refined – of carbohydrate replacing saturated fat . Additional meta-analyses looking at the effects of isolated fatty acids also generated much attention. However, these are wholly uninformative as they failed to account for food sources: people don’t eat individual fatty acids, they eat foods comprised of multiple fatty acids . Finally, the recent PURE trial – a large epidemiological study including cohorts from 18 countries –concluded that ‘high’ carbohydrate diets increased CVD mortality and that a ‘high’ saturated fat intake was protective against stroke . This conclusion is a total misnomer: by the authors own admission, they did not differentiate between whole grain and refined carbohydrate . But more erroneous was their conclusion in relation to saturated fat, because the average saturated fat intake overall in the cohorts was 8%, with the US and UK averages around 11-12%. An appropriate conclusion would thus have been: “achieving near target levels of saturated fat in the population has the desired effect of reducing CVD burden, but evidently the type of nutrient replacing saturated fat is relevant as CVD mortality rates remain high.”
If you want to get your head into some data/studies that actually matter check out the show notes to the podcast episode or get in touch and I will fire them over no problem. Everything else aside I think the long term consumption of such a high level of saturated fat is detrimental to one's health and for that reason as stated before I believe there is no decent evidence to support long term participation of the carnivore diet.
Right, I can't find any decent evidence to support that the carnivore diet inherently lowers inflammation. I found one study on a pro carnivore article that claimed a high-fat low carb diet may be more beneficial to cardiovascular health and inflammation compared to low-fat high carb diets. A couple of problems with this. The article is a prime example of cherry-picking. What they didn't say is that the study was on subjects with obesity and that the diets they were on were loosely controlled. The study concluded "This small-scale study suggests that HFLC diets may be more beneficial to cardiovascular health and inflammation in free-living obese adults compared to LFHC diets" So this whole study is based on the fact that you are obese. The article made it sound like it applied to everyone. The study its self isn't very good, to begin with, but the fact there are carnivore articles omitting key information from studies doesn't bode well for the legitimacy on other data.
What you may find online is an abundance of anecdotal evidence of people saying "I've lowered inflammation since changing it's incredible!" Yeah, they may have done that but the actual truth is is that the carnivore diet is an elimination diet. You are cutting out a large number of foods you would normally eat. The likelihood is that one of the foods you may have been eating previously could have had an effect on your body and now that it's gone it's no longer a problem. What normally happens if you are suffering from things like inflammation is you cut out certain foods and slowly introduce foods back in one by one to identify what was the culprit. As Andy said on the podcast you could go on a pop tart diet and lower inflammation but that's not inherently caused by eating just pop tarts it's because you've cut everything else out. If you do have any decent evidence to support that the carnivore diet inherently reduces inflammation then please get in touch as I'd love to see it.
Plants Are Bad: Antinutrients
Antinutrients are what their name suggests. It's food that blocks the absorption of certain nutrients. This is something the carnivore zealots have grabbed onto and blown up to ridiculous proportions. Below are common antinutrients and upon seeing this list you may start to panic and throw out all your plant-based food.
Glucosinolates in cruciferous vegetables (broccoli, Brussels sprouts, cabbage)—can prevent the absorption of iodine, which may then interfere with thyroid function and cause goiter. Those already with an iodine deficiency or a condition called hypothyroidism are most susceptible.
Lectins in legumes (beans, peanuts, soybeans), whole grains—can interfere with the absorption of calcium, iron, phosphorus, and zinc.
Oxalates in green leafy vegetables, tea—can bind to calcium and prevent it from being absorbed.
Phytates (phytic acid) in whole grains, seeds, legumes, some nuts—can decrease the absorption of iron, zinc, magnesium, and calcium. [2,3]
Saponins in legumes, whole grains—can interfere with normal nutrient absorption.
Tannins in tea, coffee, legumes—can decrease iron absorption.
Scary yeah? BUT as we always say the poison is in the dosage. The actual amount of these antinutrients is insignificant and the clear health benefits of these foods outweigh any potential negative nutritional effects. Furthermore, upon processing/cooking of these foods, it becomes a residual amount. With a balanced diet, this is not an issue. Also if you look at studies looking at those on a heavily plant-based diet containing antinutrients they generally don't show any deficiencies in iron and zinc. One article I read suggested this may be the body adapting to the antinutrients by increasing the absorption of these minerals right in the gut. It is ridiculous to tell people to stop eating these healthy foods and eat purely meat because of antinutrients. Continue to eat a well-balanced diet focusing on moderation and there is nothing to worry about.
We Don't Need Fibre
A high mixed fibre diet links to lower risk of heart disease, colon cancer and there's the also the claim that fibre makes us feel more full in turn lowering how much we will eat. Well, the carnivore diet removes fibre and those who are vocal say we don't need it. In the podcast, I mentioned a pretty large study that concluded: "Our data do not support the existence of an important protective effect of dietary fibre against colorectal cancer or adenoma." However, there is an issue with this study. Tom mentioned it on the podcast and so have other experts in the field. What were their criteria for a high fibre diet? There was none. If you're going to do a study like this there needs to be clear lines drawn and there are plenty of other robust studies that do indeed show clear links between high intakes of dietary fibre and reduced risk of heart disease & colon cancer. Once again the show notes of our podcasts episode have numerous links to studies but please get in touch if you have any concerns and I'll send over what I have. Down below is an example of a good study showing the importance of fibre.
Background: Few epidemiologic studies of dietary fibre intake and risk of coronary heart disease have compared fibre types (cereal, fruit, and vegetable) or included sex-specific results. The purpose of this study was to conduct a pooled analysis of dietary fibre and its subtypes and risk of coronary heart disease.
Methods: We analyzed the original data from 10 prospective cohort studies from the United States and Europe to estimate the association between dietary fibre intake and the risk of coronary heart disease.
Results: Over 6 to 10 years of follow-up, 5249 incident total coronary cases and 2011 coronary deaths occurred among 91058 men and 245186 women. After adjustment for demographics, body mass index, and lifestyle factors, each 10-g/d increment of energy-adjusted and measurement error-corrected total dietary fiber was associated with a 14% (relative risk [RR], 0.86; 95% confidence interval [CI], 0.78-0.96) decrease in risk of all coronary events and a 27% (RR, 0.73; 95% CI, 0.61-0.87) decrease in risk of coronary death. For cereal, fruit, and vegetable fiber intake (not error corrected), RRs corresponding to 10-g/d increments were 0.90 (95% CI, 0.77-1.07), 0.84 (95% CI, 0.70-0.99), and 1.00 (95% CI, 0.88-1.13), respectively, for all coronary events and 0.75 (95% CI, 0.63-0.91), 0.70 (95% CI, 0.55-0.89), and 1.00 (95% CI, 0.82-1.23), respectively, for deaths. Results were similar for men and women.
Conclusion: Consumption of dietary fibre from cereals and fruits is inversely associated with risk of coronary heart disease.
Pereira MA, O'Reilly E, Augustsson K, et al. Dietary fibre and risk of coronary heart disease: a pooled analysis of cohort studies. Arch Intern Med. 2004;164(4):370-376. doi:10.1001/archinte.164.4.370
Sugar Is Toxic
Yes, you read that right. Where this claim comes from is the inclusion of fructose in our diet. The liver is what processes fructose and in high amounts, you can damage the liver. Nearly all "added sugar" contains significant amounts of fructose and even "natural" sugars are roughly 50% fructose so we are consuming a fair bit of fructose in our diets. I'm going to say it again. The poison is in the dosage. The data suggest that fructose will lead to issues when consumed in excessive amounts. Well, of course, that's the case. If you have too much of most foods it's technically toxic. If you drink too much water you can poison yourself. If the carnivores want to say sugar is toxic then I'd argue with the data we have that saturated fat is toxic if you have too much of it and on the carnivore diet, it's a lot! Now I'm not going around saying saturated fat is toxic I'm just following the same train of thought of going around saying sugar is toxic. Down below is a good study that hits back at some of these questionable studies. Do not be scared of sugar. In moderation and as part of a balanced diet there should be no real issues.
"This paper reviews evidence in the context of current research linking dietary fructose to health risk markers.
Fructose intake has recently received considerable media attention, most of which has been negative. The assertion has been that dietary fructose is less satiating and more lipogenic than other sugars. However, no fully relevant data have been presented to account for a direct link between dietary fructose intake and health risk markers such as obesity, triglyceride accumulation and insulin resistance in humans.
First: a re-evaluation of published epidemiological studies concerning the consumption of dietary fructose or mainly high fructose corn syrup shows that most of such studies have been cross-sectional or based on passive inaccurate surveillance, especially in children and adolescents, and thus have not established direct causal links.
Second: research evidence of the short or acute term satiating power or increasing food intake after fructose consumption as compared to that resulting from normal patterns of sugar consumption, such as sucrose, remains inconclusive.
Third: the results of longer-term intervention studies depend mainly on the type of sugar used for comparison. Typically aspartame, glucose, or sucrose is used and no negative effects are found when sucrose is used as a control group.
Negative conclusions have been drawn from studies in rodents or in humans attempting to elucidate the mechanisms and biological pathways underlying fructose consumption by using unrealistically high fructose amounts.
The issue of dietary fructose and health is linked to the quantity consumed, which is the same issue for any macro- or micronutrients. It has been considered that moderate fructose consumption of ≤50g/day or ~10% of energy has no deleterious effect on lipid and glucose control and of ≤100g/day does not influence body weight. No fully relevant data account for a direct link between moderate dietary fructose intake and health risk markers."
Rizkalla SW. Health implications of fructose consumption: A review of recent data. Nutr Metab (Lond). 2010;7:82. Published 2010 Nov 4. doi:10.1186/1743-7075-7-82
Pesticides + Socioeconomics
It's common knowledge that pesticides are used in the agriculture industry. I know many including myself would rather they didn't but that's an entirely different discussion. The truth is is that they are used. So carnivores will say stop eating all that plant food it's covered in pesticide. 2 points I'd like to make. Firstly I hope they are aware that the animal's people eat do actually eat the plants. There have actually been tests done and on testing, they found traces of these same pesticides in animal flesh. Furthermore, unless you are buying organic meat you have the risk of the animal being exposed to antibiotics, hormones & man-made pesticides in the feed. Grass-fed beef is actually very good in terms of nutritional quality and this is normally organic anyway. NOTE while grass-fed is normally organic, organic isn't necessarily grass-fed.
Now vocal carnivores really push for the consumption of organic grass-fed meats to ensure the best quality. So if you aren't eating that then technically the argument about pesticides is irrelevant because normal meats are exposed to pesticides and the like. Let's say that everyone is getting high-quality organic grass-fed meats great. But it's not the case. Tom's favourite buzz word "socioeconomic". Religious factors impact the consumption of beef, the environmental policy will impact the amount we are going to produce so if we all wanted to go carnivore I'd be surprised if that was practical/allowed. Social impact? Also, the subsidies that are already being given to farmers would have to increase due to meat production being nowhere near as efficient as plant-based produce. Let's not forget the serious ethical issues with the amount of meat needed to feed everyone in the world. Back to the consumption of organic grass-fed as well. Are you honestly telling me people are going to be able to afford the price increase? If you're a family of 5 and you need to buy a load of steak it will really add up if you choose the organic grass-fed over the normal stuff. Example of the price difference is looking on ASDA (UK supermarket) a ribeye steak is £3.70 per steak coming in at £16.30 per kg of this particular steak cut. Now I looked online and found a farm shop offering high quality organic grass-fed beef. For 1 ribeye steak, it cost £6.85 coming in at £40.30 per kg. Now that is a ridiculous difference. The benefits of having organic grass-fed are clear but at that price, you can't be telling me every family all over the world is going to be able to afford this. Looking at various other sources as well we are looking at approximately give or take £5 per kg.
Is it boring/sustainable
Now as with any diet education is key so I'm sure there are so some creative ways of mixing it up while on the carnivore diet. I've seen some websites offering lots of different ideas however due to how restrictive this diet actually is it will get to a point where creativity is limited. As we said on the podcast, the idea of smashing meat breakfast, lunch, dinner may sound incredible at first but to me that just sounds awful. Very heavy meals and I can imagine that after a while it will get pretty boring. I suppose if you're convinced with the health reasons these carnivore zealots are telling you then you may not mind the same meals as you believe you are a healthy individual. Truth is though the claims in support are pretty rubbish so it's certainly not worth eating the same stuff day in day out for non-existent benefits.
We always say though if you find a diet that works for your goals and is sustainable then great. However when a diet is promoting excess consumption of saturated fat and telling you not to eat fibre and we have all these studies telling you to do the opposite it's hard to support it regardless if you find it sustainable or not. In terms of getting micronutrients on board, you will be told to eat things like liver, spleen, bone broth and various fish. The liver is actually a big one in terms of how much good stuff is packed inside. However, if you don't like liver then yeah that may be an issue and you will need to supplement. If you're supplementing you could argue you're not really on the carnivore diet.
Final points. Would I recommend the carnivore diet? No, I would not. If you have any concerns or think I've made some big errors then please get in touch and I'm sure we can discuss the issue. Send me some bomb-proof data and it'll be hard to argue! Are you a carnivore or know anyone who is on the diet? Get in touch and let me know your experience/thoughts on what I've said. Remember we have a full podcast episode on this topic where I, Tom and Andy go over everything in this post and more. Back next week with more health and fitness related information to wrap your brains around! Speak soon.