If you have recently started a an All-Meat diet and you find yourself “lion” around – or wanting to – more than normal, rest assured that nothing is wrong. Switching from a diet high in plant foods to one low in or completely devoid of plant foods requires the body to shift metabolic gears. Many people who go on a high fat low carbohydrate ketogenic diet often experience a constellation of unpleasant symptoms which have come to be known as the “keto flu.”

People who adopt an All-Meat diet, often experience a similar phenomenon, even if they have already become “keto-adapted” by eating a low-to-very low carbohydrate diet. Why this is remains a bit of a mystery, but it seem that some people are extremely sensitive to carbohydrates, or something in plant foods, and when they stop eating them altogether, they experience the “keto flu” all over again. This is not true for every one, of course, but it happens often enough that it is worth mentioning.

More than likely, many people are actually addicted to some of these plant foods (or other non-food keto-friendly substances such as artificial sweeteners), and – as long as they continue to ingest even small quantities of them – they avoid experiencing the unpleasant symptoms of withdrawal from these foods or chemicals.

There are other reasons besides addiction for some of the symptoms people experience when first embarking on a low-to-no carbohydrate diet. These symptoms are more a result of the changes in fluid and electrolyte balance. Carbohydrates cause the cells to retain fluid, so when you abruptly reduce or eliminate them, the cells begin to release the excess water.

A side effect of this process is the concomitant flushing of electrolytes from the body. It takes the kidneys a little while to re-organize themselves and begin preserving and recycling the minerals from the diet in a more appropriate manner for your new way of eating. This transition can take a few weeks or longer.

Another reason for some of these symptoms has to do with change over from burning sugar for energy to burning fat. These two entirely different metabolic pathways and require different enzyme systems. Up-regulating the necessary enzyme systems does not happen over night. It is a process that takes a few week or longer to get fully up and running. This is why exercise is discouraged in the adaption phase. You are no longer providing the glucose your cells have been used to, but your fat-burning capabilities are also not quite up to speed with the energy needs that vigorous exercise demands.

Danny Albers, author of the blog Primal North, wrote an excellent post about his adaptation to an All-Meat diet, which I highly recommend: Keto-Adaptaion vs. Low-Carb Limbo.

As a result, you may experience any of the following symptoms:

  • Fatigue
  • Depression
  • Brain Fog
  • Light-Headed
  • Muscle Cramps
  • Muscle Twitching
  • Heart Palpitations
  • Muscular Weakness
  • Blurry Vision
  • Keto Breath
  • Constipation
  • Diarrhea
  • Intense Thirst
  • Nausea
  • Loss of Appetite
  • Insatiable Hunger
  • Carbohydrate Cravings
  • Sleep Disturbances
  • Nighttime Urination
  • Severe Headaches
  • General Achiness
  • Hot Flashes

None of these symptoms are dangerous in the context of beginning an All-Meat diet, and they should resolve themselves within the first 2-8 weeks.

People have tried a variety of different therapeutic measures to reduce or eliminate these unpleasant symptoms. However, 99% of the time they will resolve without any alterations, additions, or interventions to the diet. Anthropologist Vilhjalmur Stefansson and early explorers who spent time with Native Arctic peoples – and eating their tradition All-Meat diet – have discussed this adaptation process in their writings.

It appears that Lt. Frederick Schwatka was the first explorer to mention the adaptation process in his diary dating back to the 1880s. While making the transition to an All-Meat diet, Schwatka, Stefansson, and others have noted that the initial few weeks can be almost incapacitating, making arduous work or travel virtually impossible. But once they have made it through a month on an All-Meat diet, most would find themselves feeling better than ever.

Stephen Phinney and Jeff Volek probably have the most comprehensive discussion of keto-adaptation in their books The Art and Science of Low Carbohydrate Living and The Art and Science of Low Carbohydrate Performance.

“Keto-adaptation is a term coined by Steve Phinney in 1980 to describe the process in which human metabolism switches over to using almost exclusively fat for fuel (i.e., a combination of fat burned directly and as ketones derived from fat). While well studied and documented mainly in the context of starvation, ketone metabolism is not well-understood by most physicians (let alone nutritionists, dietitians, trainers, and athletes) as an approach to improve health and performance.”

Many people new to the concept of a Zero Carb diet are concerned about how it will affect their athletic performance. But this study by Phinney demonstrates that once a person is physiologically adapted to a fat-based diet, their performance will actually improve:

“Steve first wandered outside the box three decades ago, performing a pair of studies that established the human capacity to adapt to very low carbohydrate ketogenic diets[6, 14]. One of these experiments was conducted in lean highly trained cyclists (VO2max >65 mL/kg/min) who normally consumed a high carbohydrate diet. The athletes performed an endurance test to exhaustion on their usual diet and then again after being fed a very low carbohydrate diet for 4 weeks. The diet consisted of 1.75 g/kg protein, <10 g carbohydrate, >80% of energy as fat, and was supplemented with minerals including sodium. Riding a stationary cycle at over 900 kcal per hour, the average performance time was almost identical before (147 min) and after (151 min) adapting to the very low carbohydrate diet. This study demonstrated complete preservation of endurance performance after 4 weeks on a diet that contained virtually no carbohydrate. There was however a dramatic shift in metabolic fuel from a heavy dependence on carbohydrate to nearly complete reliance on fat in the keto-adapted cyclists. The rate of fat use during the exercise test at 64% VO2max was approximately 90 grams per hour (1.5 grams per minute). This is over 3 times the average peak fat oxidation recorded by Venables et al[9] in 300 people that included highly trained individuals with maximal oxygen uptakes exceeding 80 mL/kg/min. Even if you cherry pick and take the participant with the highest peak fat oxidation (60 g fat/hour) observed by Venables et al[9], that value is still less than the keto-adapted participant from Steve’s study with the lowest peak fat oxidation (74 g fat/hour). On average keto-adaptation resulted in peak fat oxidation rates of 90 g fat/hour – 50% greater than the highest recorded value for any participant in Venables’ study. A couple of Steve’s keto-adapted cyclists had fat oxidation rates approaching 2 grams per minute compared to 1 gram per minute when they previously did the same exercise on their high carbohydrate diet. Thus these highly trained athletes, who already had very high fat oxidation rates, were able to dramatically increase them further – not by changing their training, but by changing their diet.”

There are quite a few interesting and complex metabolic changes that occur during the adaptation process which Phinney and Volek describe in detail throughout their ground-breaking books. Some of these changes can result in temporary and transient increases in both Uric acid and LDL cholesterol. They explain why this happens and why it is nothing to be alarmed about. He cautions people to wait about 6 months before having a lipid profile done and that people with a history of Gout may need to take prophylactic measures to prevent an attack during the adaptation period. If you are concerned about these possibilities, please read his books for a complete explanation and understanding.

Phinney’s primary suggestion to reduce the unpleasant symptoms associated with adaptation is to make sure you are consuming enough sodium chloride because this spares potassium. You can read what he has to say about this on my page dedicated solely to the subject of Salt. He also recommends the short-term use of magnesium for muscle cramps if the extra salt does not provide the desires results.

Many veterans of Zero Carb will tell you that they have tried these suggestions without much success and that adaptation is just a process that must run its course. I, however, am not convinced that these or other measures are completely ineffectual. The thing that I personally found most helpful while going through the adaptation phase was bone broth. I drank almost two quarts of bone broth every day when I was able to afford it, and I could really feel the difference when I ran out and could not afford to make more for a few days or week. Now, after almost 4 months of eating a Zero Carb diet, I no longer feel the need for bone broth, but I still make and consume it whenever possible simply because I enjoy it.

I did add salt to my bone broth, but the salt alone (when I ran out of bone broth) did not prevent my legs or feet from cramping, or my heart from beating irregularly during my first two months on Zero Carb) the way bone broth did. Bone broth contains significant amounts of the important electrolyte mineral potassium. The symptoms of potassium deficiency include muscle weakness, muscle achiness, muscle cramps, and heart palpitations, all of which are on the above list of frequently experienced symptoms during the initial Zero Carb adaptation period.

So, from my perspective – based on my own personal experience and what authors like Cate Shanahan (author of Deep Nutrition) and Kaayla Daniel (author of Nourishing Broth) have explained in their books about the many valuable aspects of bone broth (potassium being just one) – I consider it to be a potentially helpful addition to the diet when one first begins eating this way. Please read my article Can Bone Broth Be Used on a Zero Carb Diet?

For more information on the beneficial properties of this nutritionally rich elixir, please see my Bone Broth page. And again, if you choose to do nothing at all besides continuing to eat meat and drink water, all of the unpleasant symptoms you may experience should go away of their own accord after the first few weeks of eating an All-Meat diet.

In addition to their excellent book mentioned above, Phinney and Volek have given many informative lectures in which they describe the adaptation process. However, I want to make it clear that an All-Meat diet – as practiced by Stefansson and the Native Arctic peoples he lived with and studied, as well as the Zero Carb veterans I have interviewed  – is not the same as a low carbohydrate high fat ketogenic diet as promoted by Phinney and his many ketogenic diet colleagues, in the sense that there is no need to measure ketone levels, adhere to certain macronutrient ratios, or to restrict protein intake when eating only meat. For more about the Zero Carb perspective on ketones, please read my page on  Ketosis where this is explained and explored further.

Never the less, much of the science presented by Phinney, Volek and other low carb proponents still applies. Here one of my favorites (many more are available on my Resources page):

Jeff Volek – The Many Facets of Keto-Adaptation: Health, Performance, and Beyond



21 thoughts on “Adaptation

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  5. I’m wondering if anyone has experienced horrible heartburn since going Zero Carb? I was Zero Carb for about 5 weeks a few months ago and experienced the same issue. I don’t know if it is because I barely want to eat, drinking coffee or eating just from the animal kingdom, that is the cause. I am trying to drink a lot more water, which helps ever so slightly. Initially I slept so much better but now heartburn keeps me up half the night. It seems to strike about 8-9 days in. If anyone has experienced this and can advise me I’d appreciate it. I really want to stay Zero Carb but if the heartburn doesn’t clear up soon, I won’t be able to. Thank You.


    • Susan, heartburn is very often the result of low stomach acid. Taking supplemental hydrochloride acid (HCl) might prove very helpful. Please read Dr. Jonathan Wright’s book on the importance of stomach acid. You can find it on Amazon.


  6. Wondering if you have ever heard of these symptoms during adaptation: shortness of breath with chest discomfort, dry skin on hands and face, cold extremities, anger/irritability. Those are the issues I was dealing with. As soon as I ate carbs, mood improved, shortness of breath went away. I am really wondering about the safety of continuing this diet with the shortness of breath and chest discomfort. Also, I hated the way it made my skin feel/look.


    • You might trying drinking more water and supplementing with potassium gluconate powder by NOW, available through Amazon. It sounds like an electrolyte imbalance and dehydration. You lose a lot of fluid in the initial weeks of Zero Carb.


      • Thank you so much for writing back. I will try that. I’ve also been thinking that perhaps it is due to not enough fat. I notice a lot of the people interviewed ate mainly red meat and even the Bear said to eat the fat first until full. I am trying to buy fattier cuts, but I have a stupid question – the white part surrounding the red meat, is this the fat or is it something else? This white part is still there after I cook but it’s really chewy and I don’t like that; I thought fat was suppose to melt when you cooked it. Sorry for the dumb question, but I don’t cook red meat a lot (chicken with skin is more what I like).


        • The white stuff on the outside of the meat is mostly fat with some connective tissue. The connective tissue has important nutrients in it which help to keep your own connective tissue healthy and strong.


  7. Hmmm, I started this this week, after being in Ketosis for over 7 months (regularly measured through blood samples, urine strips, and breathalyzer).

    I started full zero carb on monday only and I have had diarrhea since. I wonder if this is normal, especially since I was already keto adapted.


    • Yes, bacteria in your gut changes when you eliminate plants. But certain types of fats (especially those that have been rendered) can also cause diarrhea in some people. Can you tell me what you are eating on your ZC diet?


  8. Hi Esmee, I am impressed by your blog (read length and breadth :)). I went to the ZC (I’m on the fourth day only) from LCHF. I am from the Polish and on foreign forums I find meaningful information (in Poland, the awareness is zero eh). I decided to write because for several days I feel the heart beat faster and constant, of varying severity, abdominal pain. It is strongly bulging despite a smaller portion meals. Pain diffuse, often on the left side, a centrally above and going down. I’m not overweight (167 cm, weight 54 kg). In addition, I’m tired, lethargic, but I know that this is normal. I am concerned about the belly. I have just finished the treatment of fungal infection of the vagina (One day Triaxal orally, the rest are pessaries, ointments). I eat beef, pork długodojrzewającą, bacon, lard, ghee, chicken and turkey’m going to set aside, for the moment the fish sometimes, lamb, mutton, drink water. I have the impression that the digestion is slowed down (and before I ate a lot of fat), appear bounced. I try to eat 80% fat and 20% protein. Lack of potassium? Can you handle something on this issue? Maybe something you can think of🙂. Best wishes!
    P.S. Forgive me for my English!😉
    Tłumacz Google dla Firm:Narzędzia dla tłumaczyTłumacz stronNarzędzie analizy rynków


    • The faster heart beat sounds like electrolytes. Try increasing your sodium intake first. Use at least 1 tsp of sea salt per day, more if desired. I add 1/2 tsp to each quart of water I drink. I usually drink 2-3 quarts a day. The abdominal issues sound like more of a digestive issue, or a reaction to some food you are eating. We usually recommend sticking to just beef and water for 30 days. If the beef is too lean where you live, then you will need to add butter. Try this and see if it makes any difference.


  9. Thank you for the quick reply🙂. It is to improve: heart no longer beats (I eat a lot of salt from the beginning. Adapted to.), And the belly forgiven after discontinuation of medication (suppositories), as it turned out. I’m sorry, I panicked because everything happened at one time. Cuts mięsko far different (I leave out of the freezer), but I strive to consume mainly beef, pork,. długodojrzewającej, lamb, mutton + fat, drink only water. You mention butter, I love it (accept only pasteurized!), But I still have no objections to it because of the casein and lactose, that is a form of dairy products and badly affects min. hormone. Do you have them in your menu? Regards!


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