Nutrition is a race best run as a marathon, not a sprint. And the carnivore diet is all right for an on-ramp, but not as the highway home.
If you’ve followed me for a while, you know I’m not a fan of extreme diets. That said, why then do we see so many people from all walks of life doing well on the carnivore diet—improving body composition and reporting better mood, more energy, and better digestion—if it’s also not a good diet to follow long term? Does this mean carnivore eating is a suitable diet strategy for athletes (or people in general)?
Here, I’m going to answer that with my two cents and make the case that the carnivore diet could be followed short term as a potential way to silence autoimmune issues…but it shouldn’t be followed long term. It’s also not the only path to the potential “solutions” it is correlated with.
**Abbreviated takeaways are available in the final section and you can find my comprehensive guide here.
Why Is the Carnivore Diet Problematic for Athletes Long-Term?
Although some of these health and performance issues symptomatic of a long-term carnivore diet can show up sooner in some athletes than others, here’s what tends to happen at some point or another.
Zero (or Minimal) Carbs
The carnivore diet contains zero carbohydrates. To thrive and function optimally (not just survive), carbs are essential—whether you’re an athlete or not.
Totally eliminating carbs can also impair your ability to metabolize as much glucose as before. This is the opposite of what we want for health and performance. Even carnivore and ketogenic diet followers readily admit this.Totally eliminating carbs can also impair your ability to metabolize as much glucose as before. This is the opposite of what we want for health and performance, says @rewirehp. Click To Tweet
- The primary fuel for fast-twitch muscle fibers. This matches the observed reality, wherein low-carb endurance athletes tend to be minimally explosive. To be fair, this is multifactorial, as there are multiple inputs at play here that can affect muscle fiber dynamics, including how one trains. It’s also fair to mention that fast-twitch muscle fibers aren’t the only thing that makes one fast. Sensory mechanics, fascial connectivity, and other factors contribute. That said, in my nearly 20 years in nutrition, I’ve yet to see one explosive athlete who’s done low carb for a protracted time.
- Needed to convert T4 to T3 in thyroid hormone manufacture (more on hormones later). They’re also essential for creating CO2 during the metabolic process.
- Systemically protective in the face of stresses from our environment in general, as well as for recovery from training and playing. Carbs are energy, and energy is our adaptation currency.
By eliminating/mitigating carbs (a readily available energy source), your body has to “mine” for energy from fat. This is not only energetically/metabolically inefficient for needing ready-made energy (e.g., to fuel short, athletic bursts), but it also coincides with the excessive release of stress hormones like adrenaline, norepinephrine, glucagon, and cortisol. This is one reason diets like keto and carnivore can seem like they improve energy in the short term, though this is actually fool’s gold.
Low in CO2
Forget the mainstream narrative about carbon being bad for a moment and open yourself to some nuance…CO2 is one of the primary factors responsible for us becoming more biologically complex individuals. The CO2 manufactured from carbs is a vital anti-stress, systemically nourishing nutrient.
CO2 is critical for endurance capacity and oxygenation of tissues (including working tissues during performance) via the Bohr effect. Sure, low-carb approaches can appear to work for survival-type training (e.g., hiking, obstacle course racing, etc.) because there isn’t a shot clock on energy efficiency. In repeat-burst sports like basketball, football, combat sports, and more, there is a repeat demand for an immediately available energy source.
Carb-rich diets will do this, but carb-scarce diets will not. In some of the survival-type environments I mentioned, it can appear to the individual that it’s sufficient because there’s a less limiting time stamp on the time it takes to complete the task. There’s far less urgency. The sport is less reactive in nature. Thus, it can seem (between the stress hormones and increased fat oxidation-derived energy) like the energy supply is adequate (never mind the potential survival state it’s creating under the hood).
Sports like basketball place sports car-type demands on athletes, while endurance sports place more Prius-type demands. In one case, it’s about keeping a good pace and turning on the jets regularly as need be. In the other, it’s about simply moving forward. Hare and tortoise.
Carbs are also important for vasodilation and protect against damage to proteins. They’re simply critical for maintaining/stabilizing cellular structure. “Energy and structure are interdependent at every level,” as Dr. Ray Peat would say—and in this instance, he’s right.
The diet has minimal/zero fiber. Although some fibers are indigestible, inflammatory, and problematic, no fiber/bitters can…
- Lead to poor gut motility (reduced bile flow, reduced frequency of bowel movements).
- Mean you’re not taking advantage of potential detoxification mechanisms (e.g., estrogen detox).
- Help optimize digestion when you eat the right kinds (e.g., raw carrots, bamboo shoots, white button mushrooms), even though it’s not essential. In turn, this has a positive effect on neurological function, including perception and feeling (quality of life), as well as athletic performance.
Lacking in Some Micronutrients
The carnivore diet lacks nutrient robustness, some of which can (and can’t) be supplemented effectively. Carnivore can result in nutrient deficiencies, chief among them being mineral and electrolyte balance. Even the most devout carnies concede this through a need to over-supplement electrolytes.
Electrolytes are foundational for cellular processes underpinning general health, as well as muscle actions. Electrolytes also help motor neuron communication; instead of thinking of electrolytes as simply cramp stoppers, we should think of them as physiological prerequisites to neuromuscular activity and brain health, among many, many other things.Although it is very true that plant-based eaters are highly susceptible to bone breaks, a lack of dietary calcium in meat-eaters is a possibility, too, says @rewirehp. Click To Tweet
Though not as bad as plant-based, the carnivore diet also lacks calcium. Speaking of electrolytes, calcium is difficult to get through food if you don’t consume dairy or ground eggshell powder. Most calcium supplements aren’t effective, either. If your calcium levels aren’t sufficient to support the abundant amount of phosphorus you’ll get through meat, cellular metabolism will suffer.
Although it is very true that plant-based eaters are highly susceptible to bone breaks, a lack of dietary calcium (through the false notion that dairy is inherently bad for us) in meat-eaters is a possibility, too. When I see bad bone break injuries—like the ones that happened to Paul George, Gordon Hayward, Chris Weidman, and Anderson Silva—calcium intake would be one of the first questions I’d be asking to better identify what seeded the situation.
Unless accounted for, you’ll also be deficient in collagen. If no collagen, gelatin, or bone broth is included, you’ll operate on a collagen deficiency. This means amino acids will be unbalanced in favor of amino acids tryptophan, histidine, methionine, and cystine. This may not be an issue in the short term, but this can be inflammatory and metabolically problematic in the long term.
Many athletes eating a major excess of muscle meats tend to be susceptible to various types of fatigue, which health researcher Gary Millet once categorized as “adrenal fatigue.” Collagen is also something of a fertilizer for our connective tissues, be it gut lining, hair, skin, nails, or tendons. This is a big reason why I recommend all my athletes get a sufficient amount—it’s a nutritional way to support durability on the court.
Unless modified to include some fruit, you’ll be at a deficit for vitamin C: a critical antioxidant that is immunosupportive, increases collagen synthesis (important for athletes using collagen for injury prevention and metabolism), and promotes cardiovascular health, iron absorption, and other antioxidant functions.
It’s important to remember that being low in a nutrient (or even at the recommended daily allowance, in some cases) is not the same as having optimal nutrient levels.
What Benefits Does Carnivore Seem to Have Up Front?
So, if carnivore is bad over the long term, why do people seem to report improvements in body composition, digestion, cognitive function, inflammation, and autoimmune-type symptoms? How does one explain these results?
In general, I believe most of the benefits come from cutting out dozens of inflammatory nutrients and ingredients not meant for human consumption, as well as inflammatory fibers.
Another mechanism of action is increasing nutrient content (not ideal nutrient content, mind you, but a relative increase). The carnivore diet can layer in more vitamins found only in animal products: retinol, creatine, K2-MK4, vitamin A, taurine, heme-iron, etc. This will create a highly pronounced positive effect in those coming from the plant-based or low-protein diet side of things. Simply reversing a protein deficiency can cause a significant improvement in health and subjective quality of life.
An extension of increasing relative nutrient content is increasing protein content. This also can mean improving the protein:energy ratio (P:E ratio), as coined by nutritionist Ted Naiman. I have plenty of differences with Naiman’s thoughts on the applied diet side of things, but he is right in that those with larger body composition renovation goals may need to improve their ratio of protein to both carbs and fat (energy). This is because protein isn’t so much an energy source but should be viewed more as a “free macronutrient” (to a point, as excess isn’t healthy) in that it takes more energy to fully absorb it than it contains, calorically. Those eating well beyond their caloric needs in energy often see a benefit because of this.
Additionally, carnivore can be beneficial in the form of diet-induced thermogenesis from digesting said higher protein content. This also means potentially improving energy balance (caloric intake) overall. More protein means more satiety, which means a reduced likelihood of overeating.
Circling back to nutrient inclusion, often, opening people to the benefit of ruminant organ meat superfoods (liver, heart) they weren’t intaking previously boosts the above micronutrients and more. Carnivore eating is inclusive of organ meats.
More Gut Rest, Less Inflammation
This warrants more elaboration. The nature of carnivore translates to more gut rest—meaning the carnivore diet acts as something of a fasting mimetic by being a low-residue diet. This means most of the food is digested in the small intestine quite quickly.
The increased energy, cognitive fitness, and symptom suppression can also result from a combo of having fewer energy-stealing, brain fog-promoting inflammatory agents and upregulated production of adrenal stress hormones like cortisol.
Aspects of Dr. Steven Gundry’s work can be pulled from here to help us understand the underlying why’s: namely, plant defense chemicals, bacterial endotoxin, and excessive and/or semi-indigestible fibers.Many health and performance issues start in the gut. Resolving gut insults and rehabilitation from gut injury is a priority for athletes, says @rewirehp. Click To Tweet
Plant defense chemicals and “anti-nutrients” are compounds that plants use to defend themselves. Even to the uninitiated, this should make intuitive sense. We’ve all heard that plants may be poisonous to prevent animals from eating them. Think of this as a less dramatic version of that. While many fruit-bearing plants with seeds like strawberries prefer that we eat them because it helps proliferate the species when they come out the other end, there’s no biological advantage in being eaten for many plants. Thus, poisons (both high-level and low) and indigestibility are their inherent defense mechanisms.
Plant toxins include lectins, tannins, oxalates, goitrogens, trypsin inhibitors, and self-made pesticides. These can prevent the absorption of what nutrients a plant may contain, disrupt the hormonal profile of the consumer, inhibit the release of digestive enzymes and stomach acid, and even cause organ failure or death in extreme cases. Plant toxins can sometimes be produced or upregulated in response to stressful growing conditions; in turn, these plants can even communicate to neighboring ones to do the same.
Both animals and humans have built-in evolutionary adaptations that help keep us safe from these plant insults.
Ruminants like cows actually have a quad-series stomach complete with bacteria-filled rumen that helps them neutralize and break down plant toxins. We humans don’t have this built-in machinery. We have an acidic, bacteria-free stomach like dogs, cats, or vultures. When ruminants are left to their own devices and roam freely, they actually rely on their senses to avoid consuming an excess of plant toxins. However, if hypothetically caged with limited food options, they will override these instincts and consume what’s available.
Cows tend to find those plants poisonous to them unpalatable and unappetizing. They won’t usually eat them unless their feed is contaminated with them or they don’t have other food options. As health researcher Kaya of Fundamental Nourishment points out, some of the best plant toxin neutralizers are sheep, and even they aren’t bulletproof. They can experience thyroid dysfunction, congenital hypothyroidism, thyroid goiters, stillbirth, and even death from simply overconsuming kale.
In fact, research has shown thyroid enlargement (goiter) in lambs fed an excess of kale compared to pasture-raised lambs that were left to choose what they ate—one example of seemingly innocuous plant toxins disrupting hormone function and overall health. Not identical in humans, but surprisingly similar health consequences.
These goitrogens can disrupt our thyroid function by inhibiting iodine utilization, which diminishes the production of thyroid hormone T4 and its conversion into the active thyroid hormone T3. They also can hyper-elevate the pituitary hormone T.S.H. (thyroid stimulating hormone), which is associated with systemic inflammation at too high a clip. Although other plant toxins can disrupt the thyroid, goitrogens like kale, broccoli, cauliflower, rutabaga, cassava root, and turnip are the worst offenders (goitrogen). Other plant toxins can, however, be a stick in the bike spokes to liver function—the chief conversion site of T4 to T3.
Humans have the same palatability instincts. Well-cooked kale tastes better than raw. Peeled carrots taste better than unpeeled ones. Cooking mitigates many plant toxins, as does removing the peel, where many of these toxins are concentrated.
Oddly enough, momma may not have known best when she force-fed some of these vegetables to us as kids. Kids are generally more oriented toward their instincts and have not yet been trained to follow what they “ought to do” food-wise, yet. It turns out we may not need to suck it up, nor are we worthy of ridicule for being weak-willed. This is our instincts guiding us in many cases.Just because some plants contain nutrients, it doesn’t mean we’re able to absorb them. There’s a big difference between nutrient presence and bioavailability, says @rewirehp. Click To Tweet
It’s also important to remember that just because some of these plants contain nutrients, it doesn’t mean we’re able to absorb them. There’s a big difference between nutrient presence and bioavailability. There may not be much use in selecting certain plants or grains based on nutrient contents if you can’t utilize them.
This slots into our digestion—absorption—utilization nutrition model quite well. If you can digest something, you can absorb it. If you can absorb it, your body can utilize it as it was meant to. Nutritionist Ronnie Smith of Energy Concepts originally conceived this nutritional model. (Ronnie also took a bioenergetic view of health and performance.)
Removal of these digestive and neuroimmune insults results in a drastic upfront minimization of gut injury for most. A reduction in them (and the other listed digestive insults) is responsible for a good amount of the benefits, including visual body composition changes. Some of those results stem from not having as much gut inflammation, water retention, and bloating.
We’re essentially providing a pruning effect on unwanted bacterial overgrowth (in some cases), bacterial endotoxin, and more—not unlike how environmentalists intentionally introduce certain animals to get rid of invasive species to balance out ecological systems. And this isn’t purely an analogy—your gut literally is an ecological system.
Because we know the gut and brain are linked via the gut-brain axis, a bidirectional link between the central and enteric nervous systems, this means emotional and cognitive centers of the brain are linked with peripheral gastrointestinal function.
It’s not a stretch to say that we can presuppose this not only applies to neuropsychiatric conditions like mood but also has implications with the neurological efficiency required for high-level performance. Your physiology doesn’t work in silos but as one coordinated unit—just like your movements.
While many will scoff and say, “look at high-level athletes who eat crap, like D.K. Metcalf,” the reality is that some elite-level athletes have the superpower of being able to overcome bad environmental inputs compared to you and me.
For the overwhelming majority of us who need to put in work to be great? Good luck, if that’s your approach.
Reduction of Bacterial Endotoxin
Speaking of, another thing that makes carnivore highly effective up front is the diet’s ability to prune away at bacterial endotoxin efficiently. Not unlike the gut irritants I mentioned, bacterial endotoxins are a key driver of gut (and neuroimmune) issues that have many downstream health and performance implications.
The short-term benefits of the carnivore diet can come from “addressing” some of the above gut issues, which in turn relieve some hormonal issues that present with most modern diets. Additionally, this can help reduce serotonin (a neurohormone) that limits metabolic function. This means braking ATP production, which in turn downregulates us into more of a “hibernating” state. As a reminder, you need energy to adapt to the stressors of playing and training, as well as modern life.
Another underlying mechanism is cortisol and stress hormones that kick in as a result of sticking more to the right side of the Krebs cycle and biasing mostly fat oxidation (mobilizing dietary and body fat into energy instead). This is because the body doesn’t have an immediately available energy source (carbs). When the body goes to “mine” its own energy, it releases stress hormones such as cortisol and glucagon.The ‘high’ many people report is essentially because they’re running on stress hormones—not because they’ve unlocked a higher level of cognitive fitness, says @rewirehp. Click To Tweet
Short-term, cortisol (the “stress hormone”) can be anti-inflammatory as a stress response, but prolonged, perpetual release in excess is harmful and will suppress your metabolism. If protracted, it can also contribute to degenerative states (as one of many factors). This “high” many people report is essentially because they’re running on stress hormones—not because they’ve unlocked a higher level of cognitive fitness. Generally, this also can disrupt sleep cycles (an area where athletes are already working against the odds when they’re traveling on road trips).
However, hormones are yet another net negative. On top of chronic upregulation of stress hormones, the carnivore (and keto) diet can dunk on your hormones by increasing SHBG (sex hormone binding globulin), lowering GnRH (gonadotropin-releasing hormone), and lowering T3, as we mentioned before.
Once again, we’re playing the carnivore chorus. The central theme is that being ahead in the first quarter ain’t the same thing as winning the game. A short-term stepping stone isn’t the same thing as a long-term solution.
“Action Items” and Considerations for Integration
Although there are more layers to this, I hope this section gives you a solid understanding of why carnivore can be a great shortcut but not a complete dietary template. What can carnivore eating teach us? What nuggets can we potentially fold into our own regimen? Whether it’s something to do or not to do, I believe we can learn some things from the carnivore diet.
The reality is that people get results up front with the carnivore diet because it gets most people eating more protein (and most aren’t eating enough). Most need to eat more protein, but keep in mind some athletes and gym goers may have overeaten protein to a detriment.
It’s been responsible for many learning the benefits of organ meats—and that’s a good thing. Ruminant organ meats are nutrient powerhouses. Regularly include these. Once per week should be solid for most, though certain high-stress situations such as the energy demands of professional-level athletics may call for more.Ruminant organ meats are nutrient powerhouses. Regularly include them—once per week should be solid for most, says @rewirehp. Click To Tweet
It improves the protein:energy ratio by having people consume less energy in the form of carbs/fat while upping protein, which is thermogenic. It cuts out dozens of processed ingredients, stabilizers, and inflammatory ingredients not meant for human consumption, and it also cuts down on inflammatory fibers found in certain plants.
It’s helped usher in the correct notion that saturated fats and cholesterol foods aren’t evil—quite the opposite. These are like fertilizer for protective, anti-stress, steroid hormone manufacture. It’s the so-called “heart-healthy polyunsaturated fatty acids” (especially industrial seed oils) that are to be avoided. Unfortunately, many pro sports franchises’ chefs cook with these oils. This is one of many examples that gets overlooked by training staff—what good is the latest force plate technology if athletes are being fed slow-acting poisons? I’m all for a lot of sports science technological innovations, but worrying about data without fixing the fundamentals is like majoring in the minors.
It helps us rethink mainstream vegetable integrations. Lettuce, most salads, highly cruciferous vegetables, and leafy greens are to be minimized, for the most part. Vegetables like raw carrots, white button mushrooms, and bamboo shoots are to be emphasized. That said, carbs and quality vegetables aren’t evil just because certain junk food carbohydrates are bad for our health.
Most of the benefits come from improved gut health, as carnivore is a low-residue, high gut motility diet. (That’s just a nerdy way to say it mimics fasting by digesting food in the small intestine immediately.) Many health and performance issues start in the gut. Resolving gut insults and rehabilitation from gut injury is a priority for athletes.
The bigger picture here is that carnivore is a low-energy diet (both in a macro and micro sense) as well as an inducer of systemic stress that—if prolonged—resembles survival states. It’s a black-and-white approach that makes some improvements that get attributed to the broad brushstroke of meat only. The key to remember here is that symptom suppression is not the same thing as addressing the root cause, and THIS is why it can be a dangerous mirage. In reality, you could accomplish the same benefits and more with a chisel instead of a sledgehammer (small tweaks versus a giant extreme, sweeping change).
There could be a gut-reset benefit to following the carnivore diet for a couple of weeks at a time, but if you decide to do this, be sure to include some digestion-friendly fiber in the form of raw carrots, white button mushrooms, bamboo shoots, etc. as well as not give up sugar from the small amounts of carbs you allot yourself during this time. This means still including fruit, fruit juice, raw honey, and milk (not just a carb, but mostly carb-dense in terms of macro spread).
Truth is, it’s another example of a sledgehammer diet. By that, I mean you take one giant hammer swing and eliminate a food group, key nutrient, etc., and then decide that all the benefits you’re getting come from cutting out something like carbs, meat, etc. when in reality it created a ripple effect of a lot of smaller changes under the hood, physiologically speaking (both good and bad). Was it really the meat or carbs, or was it a combo of all the small things under the hood that changed as a downstream consequence?
That’s why all these extreme diets don’t work well in the long run. Better to use a chisel and find what works for you over time: how much to eat, dialing in your grams of protein/carb/fat macronutrients, identifying what nutrients you need more of, and testing what’s causing inflammation rather than doing an extreme sledgehammer diet.Athletes considering a temporary carnivore approach should only do so for two weeks during a time when they’re not playing, says @rewirehp. Click To Tweet
Even if you use carnivore as a reset, don’t mistake the current on-ramp for the long-term highway. Athletes considering a temporary carnivore approach should only do so for two weeks during a time when they’re not playing. This likely means early off-season for pro athletes. Everyday individuals should take a deload from training.
The bottom line with carnivore is it can be a useful ultra-short-term tool as an elimination diet to identify food sensitivities and stabilize your gut situation in dire situations. Beyond that, you’re better off as the tortoise than the hare in this race.
Since you’re here…
…we have a small favor to ask. More people are reading SimpliFaster than ever, and each week we bring you compelling content from coaches, sport scientists, and physiotherapists who are devoted to building better athletes. Please take a moment to share the articles on social media, engage the authors with questions and comments below, and link to articles when appropriate if you have a blog or participate on forums of related topics. — SF