Carnivore Diet: The Best Diet For Men?

Take-home points  

• Most people will probably lose weight on a carnivore diet (eating only meat) but find it hard to maintain.
• Components of the carnivore diet (e.g. low fibre and antioxidants, high saturated fat) do not align with recommendations for cardiovascular health.
• Not eating plant foods increases the risk of nutrient deficiencies, with potentially devastating health consequences.
• We recommend high caution when digesting information about the carnivore diet; many carnivore advocates are overstating the benefits and dismissing the risks.

What is the carnivore diet?

Adding to the list of extreme diets that disregard conventional nutrition advice is the carnivore diet—and this may be the most extreme one yet. It is simple: eat only meat. As long as the constituents of a meal have walked, flown or swam, they can be eaten without limitations. But no fruits. No leafy greens. No grains, beans, tubers, herbs or spices. Just meat. Flexible carnivores will eat eggs, dairy, fatty meat products (tallow and lard) and condiments (salt and pepper) in small amounts at a push.

The popularity of the carnivore diet has increased substantially in the last few years. Facebook pages dedicated to the carnivore diet are approaching 100,000 members, carnivore diet books are among the best sellers on Amazon, and several carnivore advocates have reached millions of listeners through podcasts (even The Joe Rogan Podcast). Most likely, the extremity of the carnivore diet has captured people's attention. Claims that people feel ‘lighter, stronger, and faster’ are also hard to ignore.

The question is, does the carnivore diet deserve the hype?

The carnivore diet versus standard diets  

The carnivore diet may sound extreme, but short-term benefits of the carnivore diet for the average person are likely. Saying no to every food other than meat will make it hard not to lose weight, which is enough for many people to feel better in their skin. For people who are overweight or obese (1.9 billion adults), weight loss alone improves the quality of life, sleep quality, and sexual function, among other health benefits.¹  

However, the elephant in the room is that 50% of the average person's diet is ultra-processed food ²—think cakes, cookies, pizza, and refined cereals—so any new diet restricting common junk foods is bound to benefit. We would argue the benefits of elimination diets often speak more to the poor quality of the average person’s diet, rather than the high quality of elimination diets. In either case, people's success on the carnivore diet is unsurprising; people have reported similar benefits with the cabbage soup diet (eat only cabbage soup) and the liquid diet (only drink liquids, no food).  

We emphasise that diets should not be recommended based on social media reports or reviews. Instead, diet recommendations should be backed with scientific investigations that pass a few sanity checks. What are the long-term benefits of the carnivore diet? What are the long-term risks? How does it compare to other recommended diets? Who is it suitable for? Is it sustainable? Large amounts of research to answer these questions is why healthcare professionals recommend some diets (the Mediterranean, Nordic and DASH diets, for example) and not others.  

The carnivore diet has not been rigorously studied

Unfortunately, no rigorous study has investigated health changes before and after the carnivore diet.

To our knowledge, the only study on a group of carnivore dieters is a survey of 2,029 carnivore dieters who followed the diet for at least six months.³ In this study, survey responders reported high satisfaction with the diet, minimal adverse effects and an array of health benefits, including weight loss, improved digestion and reduced use of insulin medications. However, this type of study is considered extremely weak by scientific standards. One glaring issue is that the accuracy of the health information submitted by the respondents cannot be checked. The other major issue is that people who tried a carnivore diet and stopped within six months, for health reasons or other, were excluded from the study. Self-reports in this survey also showed that LDL-cholesterol, a major risk factor for cardiovascular disease, increased substantially from 126mg/dL to 172mg/dL while on the diet.³

Are we evolved to thrive on the carnivore diet?  

Despite the lack of research on the carnivore diet, advocates of this approach will claim that we are evolved to thrive on this diet, as our ancestors consumed only meat for millions of years. But there are a couple of problems with this line of reasoning.  

Firstly, the diet that humans have traditionally eaten throughout history does not mean it is the healthiest diet today. This would be an ‘appeal to nature fallacy’, when someone claims something is good because it is natural. There is also evidence to counter this argument. For example, even in deceased Inuits, who ate a near-carnivorous diet, we see they still suffered from severe amounts of plaque in their arteries.⁴ Hunter-gatherers are often used as an idealistic example of human health, but the average life expectancy of these populations was around 30 years old, less than half of the average lifespan today.  

Secondly, plants were a part of almost all ancestral diets, regardless of location or time. One type of human species (Neanderthal) arguably ate mostly meat; however, there have been 21 types of human species and Neanderthals only contributed a small amount of genetic material to modern humans (or none to people of African origin). Moreover, plant remains and residue on stone tools and remaining dental structures have been found in most ancestral regions in Europe, Africa and Asia.⁵ The dietary habits of modern-day hunter-gatherer populations such as the Hadza also suggest that plants were a major component of evolutionary diets.⁶ It is therefore likely that humans evolved with a mixed diet, with the proportion of plant and animal foods dictated by location, season and food competition.

Required foods vs. desirable foods  

One argument for the carnivore diet is that plant foods and carbohydrates are “not required” in the human diet. However, it is important to note that what is required in the human diet is different from what is desirable. The same can be said of exercise; there is little doubt that exercising is beneficial despite not being required to live. For the same reasons, it is unlikely that people will experience dramatic consequences when abstaining from plant foods in the short term, but this does not dismiss research showing that higher consumption of nuts,⁷ legumes⁸ and wholegrains⁹ reduces the risk of cardiovascular disease and overall death. There is probably no way to navigate around this on a carnivore diet; many of the benefits of plant foods stem from their dietary fibre¹⁰ and antioxidant content,¹¹ which are largely absent from animal foods.

The risks of the carnivore diet

Nutrient deficiencies with the carnivore diet  

Ensuring a diet offers a sufficient amount of all essential nutrients (vitamins and minerals) is essential when reviewing the quality of a diet. Nutrient deficiencies cause serious and sometimes irreversible health issues. Unfortunately, the prevalence of nutrient deficiencies among people following a carnivore diet is unknown. Carnivore dieters have claimed that everything humans need is within animal foods, but there is reason to believe that meeting the recommended daily amounts (RDA) of essential nutrients is extremely challenging on a carnivore diet.  

Health experts from Red Pen Reviews, who reviewed the most popular carnivore diet book, found that even the sample meal plan in the book was deficient in vitamin C (60% of RDA), vitamin E (41%), vitamin K (16%), magnesium (60%), manganese (78%), potassium (70%) and calcium (29%; without supplementation). It was also inadequate in vitamin D, but every other diet is too without supplementation. Vitamin D is mostly obtained from sunlight, fortified foods or supplements.  

As previously explained, there are also non-essential but desirable food components such as dietary fibre and antioxidants, largely absent from animal foods. A low dietary fibre and antioxidant intake is likely worse for overall health than high intakes.  

The carnivore diet and cardiovascular health

Another major concern with the carnivore diet is a potentially detrimental effect on cardiovascular health. Specifically, that an animal-based diet with a high saturated fat content can greatly increase LDL-cholesterol, which the European Atherosclerosis Panel states is one of the major causal risk factors for cardiovascular disease.¹² Experts have raised cardiovascular concerns for animal-based ketogenic diets,¹³ so the carnivore diet is subject to the same criticism.  

We understand that carnivore advocates have claimed that LDL-cholesterol is not problematic if someone is generally healthy; however, currently available evidence does not support this. A pre-published study found that among metabolically healthy women with a low risk of cardiovascular disease, high LDL-cholesterol still predicted a higher overall risk of dying relative to normal LDL-cholesterol. Even “normal” LDL-cholesterol levels have been associated with plaque development in the arteries in the absence of other cardiovascular risk factors.¹⁴ For this reason, cardiologists are starting to recommend that LDL-cholesterol is lowered as much as possible to optimally reduce the risk of cardiovascular disease¹². Yet, the carnivore diet is unlikely to lower LDL-cholesterol at all.

That said, LDL-cholesterol is not the only determinant of cardiovascular risk. Other cardiovascular risk factors (e.g. blood pressure and systemic inflammation) are potentially impacted. For this reason, although people will not optimise their cardiovascular health on a carnivore diet, it may not be as harmful as implied by changes in LDL-cholesterol alone. Unfortunately, no high-quality studies can inform us otherwise.  

References  

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