Recently I wanted to explore the world of Ketosis. I thought I knew a little bit about ketosis, but after doing some research I soon realised how wrong I was. 3 months later, after reading numerous books, listening to countless podcasts and experimenting with various diets I know have a sound understanding of ketosis.
This resource is built as a reference guide for those looking to explore the fascinating world of ketosis. It is a resource that I wish I had 3 months ago. As you will soon see, a lot of the content below is not mine, instead I have linked to referenced to experts who have a greater understanding of this topic than I ever will.
I hope this helps and if there is something that I have missed please leave a comment below so that I can update this.
Also, as this is a rather long document, I have split it into various sections. You can click the headline below to be sent straight to the section that interests you.
Peter Attia from EatingAcademy.com, a leading expert in the field of ketosis, defines it as:
A state where your liver makes enough ketones to offset the brains dependence on glucose – P. Attia.
For more of a detailed explanation refer to Dr Peter Attia’s interview on the Tim Ferris Show. At about the 20minute mark, Peter does a great job of explaining ketosis. You can listen to this HERE.
Otherwise I have paraphrased some of his comments below:
“Our ancestors lived in a time when we would go without food for extended periods. The human body can only store a finite amount of glucose (sugar). Some in the muscles, and some in the liver. Only the glucose stored in the liver can be utilised by the brain.
The brain uses about 20% of our daily metabolic fuel needs, and ordinarily functions using glucose. So we have a problem, the brain is dependent on glucose, but we can only store a small amount of glucose in the liver.
The body needed a system to fuel the brain (and the body) even in times where there was no readably available food. Converting protein to glucose was one possible mechanism – but this would mean a lot of muscle wasting which isn’t wise for our survival.
The other option – which is the superior option – is the breakdown of fat into a fuel that can be used by the brain. This is a beautiful solution, because even the leanest individual will have weeks and weeks’ worth of energy stored as body fat. The body breaks down this fat in the liver and converts it into ketone bodies. The brain can then utilise these ketones as a fuel source – forgoing the need for stored glucose or constant consumption of carbohydrates. These ketones can also be used to make ATP.
The body will start making ketones when either we go extended periods without food, or we restrict the one dietary component that stops ketone formation – this being carbohydrates and also minimising protein intake as this also can halt ketone. In turn, your primary source of food is fat, with very little carbohydrate and a small amount of protein.”
Meanwhile Ben Greenfield, a health and fitness guru who also has a lot of experience with ketosis and athletic performance defines Ketosis as:
Ketosis is a metabolic state where most of the body’s energy supply comes from ketone bodies in the blood, in contrast to a state of glycolysis where blood glucose provides most of the energy. Ketosis is characterized by serum blood concentrations of ketone bodies over 0.5 millimolar with low and stable levels of insulin and blood glucose. However, with ketone supplementation (as you’ll learn about later in this article) ketosis can actually be induced even when there are high levels of blood glucose
Finally, for a more ‘scientific’ definition of ketosis (and a rather long one!) let us refer to the 2013 paper in the European Journal of Clinical Nutrition, which defined Ketosis as:
After a few days of fasting, or of drastically reduced carbohydrate consumption (below 50 g/day), glucose reserves become insufficient both for normal fat oxidation via the supply of oxaloacetate in the Krebs cycle (which gave origin to the phrase ‘fat burns in the flame of carbohydrate') and for the supply of glucose to the central nervous system (CNS).4
The CNS cannot use fat as an energy source; hence, it normally utilizes glucose. After 3–4 days without carbohydrate consumption the CNS is ‘forced' to find alternative energy sources, and as demonstrated by the classic experiments of Cahill and colleagues4 this alternative energy source is derived from the overproduction of acetyl coenzyme A (CoA). This condition seen in prolonged fasting, type 1 diabetes and high-fat/low-carbohydrate diets leads to the production of higher-than-normal levels of so-called ketone bodies (KBs), that is, acetoacetate, β-hydroxybutyric acid and acetone—a process called ketogenesis and which occurs principally in the mitochondrial matrix in the liver.6
Ketone Bodies are then used by tissues as a source of energy3 through a pathway that leads to formation from β-hydroxybutyrate of two molecules of acetyl CoA, which are used finally in the Krebs cycle. It is interesting to note that the KBs are able to produce more energy compared with glucose because of the metabolic effects of ketosis—the high chemical potential of 3-β-hydroxybutyrate leads to an increase in the ΔG0 of ATP hydrolysis.3
We would like to emphasize that ketosis is a completely physiological mechanism and it was the biochemist Hans Krebs who first referred to physiological ketosis to differentiate it from the pathological keto acidosis seen in type 1 diabetes..
Why would one want to be in a state of ketosis? There have been a lot of documented reports behind the benefits of ketosis. I cover these in depth in my article 24 Benefits of the Ketogenic Diet.
Some of these benefits include:
Again, I cover this topic in much more detail in this article.
Ketoacidosis is dangerous. Ketosis however isn’t.
For a brief overview of the difference between these two states see the following clip:
Ketoacidosis is a serious condition and can be life threatening. Ketosis on the other hand is something that most people enter every night when they are sleeping. There is a big difference. Many doctors are only familiar with ketoacidosis and thus get the terms mixed up – hence the common fear of ketosis being dangerous.
The difference between the two conditions is a matter of volume and flow rate*:
… ketosis is a controlled, insulin regulated process which results in a mild release of fatty acids and ketone body production in response to either a fast from food, or a reduction in carbohydrate intake.
Ketoacidosis is driven by a lack of insulin in the body. Without insulin, blood sugar rises to high levels and stored fat streams from fat cells. This excess amount of fat metabolism results in the production of abnormal quantities of ketones. The combination of high blood sugar and high ketone levels can upset the normal acid/base balance in the blood and become dangerous. In order to reach a state of ketoacidosis, insulin levels must be so low that the regulation of blood sugar and fatty acid flow is impaired.
Included is a graph showing the levels of ketones in the blood in varying ketosis states:
As per the image, you can see ketoacidosis has ketone levels of 20 mmol or higher. Meanwhile ketosis only brings about 5 mmol/l of ketones in the blood. Even going 20 days without food doesn’t bring about a ketone reading even close to that of the ketoacidosis.
As Jimmy Moore states in his Keto Clarity book:
A ‘.. key point to keep in mind is that the rise in blood ketone levels that leads to ketoacidosis is diabetics corresponds with a simultaneous elevation of blood glucose levels. But when ketosis is used for therapeutic purposes in everyone else, blood glucose actually drops. This is a major difference that should help put your mind at ease’
For more on this topic, be sure to read Dr Peter Attia’s article ‘Is ketosis dangerous?’
As always, please consult a medical professional before undertaking any dietary changes.
Being on a low carb diet does not mean you are in ketosis or in a ketogenic state. There is a big difference between the two.
Being in a state of ‘ketosis’ generally means you have a ketone blood reading of 0.5mmol/l or higher (more on how to track this figure below). But you can be on a low carb diet and not be anywhere near 0.5mmol of ketones in your blood.
In fact this was one of the biggest surprises I had when exploring ketosis. For years I have been following a cyclical lower carb diet. For years I wouldn’t consume a carb until later in the afternoon (ala Carb Backloading style). After eating 5 days without any carbs I tested my ketone levels… they were 0.1 mmol. This reading was done first thing in the morning (10 hours fasted) after 5 days without a carb in my diet.
To be clear, low carb does not equal nutritional ketosis (more on nutritional vs therapeutic ketosis below). Refer back to the graphic above, you can see how after a night fast that some ketones are present but it is such a low amount.
So what is the difference between low carb and keto?
First you need to define what you mean by low carb?
Given that the average American male adult consumes about 250-300g of carbs a day then you could define a low carb diet as anything below 250g of carbs a day.
Mark Sission of Marks Daily Apple fame recommends adjusting your carb intake based on your fat loss goals and your exercise output with his Carbohydrate Curve. In this curve you will see he recommends 150g or below for most people:
His primal diet is often considered to be a typical low carb diet.
Some people follow more of an Ultra Low Carb diet approach. This is generally around 50g or less of carbs per day. A ULC is more supportive of reaching a ketogenic state, but again total carbs are not the only variable when it comes to reaching ketosis (other factors such as types of carbs, protein consumption, portion size, ingredients, supplements used etc. all play a role and will be covered in more detail below).
Next you need to define what you mean by ketosis. S. Phinney and J. Volek in their book ‘The Art and science of Low Carb Performance’ state the optimal range for ketosis being between 0.5 and 3.0 mmol of ketones in the blood. This can be seen in the following graphic:
In summary, ketosis is a state of being when your blood ketones are in a range of 0.5 to 3.0 mmol. Low carb is simply eating a low carb diet.
Can you be low carb and in ketosis – Yes and No.
Do you have to be low carb in order to be in ketosis? No.
If you are confused, read on as I will explain this in more detail below. But just remember – being in a state of ketosis means more than simply restricting carbs. Limiting carbs does help, and typically the lower your carb consumption the more likely you will be in a state of ketosis, but there are other factors that come into play.
There are multiple forms of ‘ketosis’. The conventional way to enter ketosis is to eat an ultra-low carb, protein restricted high fat diet (more on this below). This would be considered ‘Nutritional Ketosis’.
But some people chose to use supplements to benefit from ketosis (Therapeutic Ketosis), and finally there is the MCT Ketogenic Diet – which in a form of nutritional ketosis (ULC, limited protein, high fat) with a twist – about 30-60% of the fat intake in the diet comes from MCT (Medium Chain Triglyceride) fats. Sources of MCT fats include Pure MCT Oil, Coconut oil and coconut products. The MCT Ketogenic Diet is often used with epilepsy suffers, as the high levels MCT oil create a higher level of ketones in the blood – which helps prevent seizures.
For more on the MCT ketogenic diet and epilepsy please see THIS page.
HeadupsUpHealth.com in their article Eight Great Ketogenic Diet Benefits do a great job explaining the difference between Nutritional vs Therapeutic ketosis:
There are two primary methods to obtain the benefits of ketones for your own health:
- Follow a ketogenic diet (nutritional ketosis): By following a diet that is high in fat, modest in protein and low in carbohydrate, we can naturally induce our body to start burning fat for fuel and producing ketones.
- Take ketone supplements (therapeutic ketosis): A second option is to consume ketones in the form of a supplement. Supplements provide the exact same ketone bodies that are produced naturally in the body. And while supplements are not a complete replacement for the benefits of ketones produced through diet, they do lower the barrier by allowing anyone to start benefiting from therapeutic ketones.
Hybrid strategy: A hybrid strategy is to follow a low-carb/high-fat ketogenic diet to induce nutritional ketosis and use ketone supplements strategically. Supplements can help ease the transition into ketosis, they can be an effective tool when we are knocked out of nutritional ketosis and they can help push ketone levels higher in the body for added benefit.
For a great overview of the various types of Ketogenic diets, and their therapeutic use please see this chart put together by the Charlie Foundation.
Finally, for a interesting view of how MCT oil can help with ketone production (while still having a moderately amount of carbs in the diet) please see this video by Chris Masterjohn:
Is a ketogenic diet safe?
This is quite a controversial question.
There have been studies done on long term ketogenic diets. This 2004 paper inn Experimental & Clinical Cardiology titled ‘Long-term effects of a ketogenic diet in obese patients’ concluded that obese patients following a ketogenic diet for 24 ‘reduced the body weight and body mass index of the patients. Furthermore, it decreased the level of triglycerides, LDL cholesterol and blood glucose, and increased the level of HDL cholesterol. Administering a ketogenic diet for a relatively longer period of time did not produce any significant side effects in the patients. Therefore, the present study confirms that it is safe to use a ketogenic diet for a longer period of time than previously demonstrated.’
Meanwhile Brinkworth, et al., in their 2009 paper "Long-term Effects of a Very Low-Carbohydrate Diet and a Low-Fat Diet on Mood and Cognitive Function" looked at the effects on ketogenic diet on cognitive function and mood. The study participants ate a ketogenic diet for a year and the researchers found that mood levels decreased when compared to a group eating a high carb/low fat diet. They go on to remark “there was no evidence that the dietary macronutrient composition of LC and LF diets affected cognitive functioning over the long term, as changes in cognitive function were similar for both diets”.
Also they found that both groups (ketogenic and the low fat group) had similar levels of weight loss.
Children who followed a ketogenic diet for 2 years showed stunted growth, which was reversed in a ‘catch up period’ (eating a normal diet) as found by Kim et al in their 2013 paper.
Fans of ketogenic diets commonly point to the Inuit and how they have survived for generations while eating a lower carb, ketogenic diet. To read more on this please see this review - Ketogenic diets and physical performance by Stephen Phinney.
But there have also been studies done showing that the Inuit Eskimo’s do not actually reach a state of ketosis. This is due to numerous factors. One being that the diet the eskimo’s eat ‘would not be expected to cause ketosis, because the calculated anti-ketogenic effect of the large protein ingestion was somewhat more than enough to offset the ketogenic effect of fat plus protein.”
The breakdown of traditional Eskimo diet worked out to be:
280g/day of protein o 135g/day of fat o 54g/day of carbohydrate (“of which the bulk is derived from the glycogen of the meat eaten).
Finally, the author of the 1928 study paper concluded ‘On normal diet, Eskimos showed no evidence of ketosis and had high glucose tolerance (unlike most modern ketogenic dieters, who fail oral glucose tolerance tests while in nutritional ketosis)’.
This claim was later supported by Corcoran and Rabinowitch in 1936 who stated:
[There was an ]“…absence of ketosis in these natives.”
“Though the small amount of carbohydrates in the diets may be more than balanced by the potential sugar production from the large amount of protein to keep the ratio of fatty acid to glucose below the generally accepted level of ketogenesis, the respiratory quotient data suggest another mechanism also” ß (most likely the CPT-1A mutation, which had not been discovered at that time)
It has been shown that Inuit Eskimos possess a genetic mutation that prevents ketosis as per these papers - http://www.ncbi.nlm.nih.gov/pubmed/19217814 and http://www.cell.com/ajhg/abstract/S0002-9297%2814%2900422-4
Also, this experiement should be of interest. Two men followed a ‘traditional Eskimo’ diet for 1 year. After the year eating a low carb high fat diet, it was found that the men had a diminished tolerance to carbohydrates, something that did not occur in Eskimos eating the same diet. It took the mean nearly a month of eating a ‘normal diet’ before their glucose tolerance returned to baseline.
All these papers indicate that the ‘eskimos have been eating a ketogenic diet for generations and are fine’ argument is not necessarily a justifiable point to support the notion that ketogenic diets are safe for individuals with a western heritage.
There is also a growing belief that ketosis is actually a stress on the body, and is a mechanism used in times of low food availability. Danny Roddy does a great job explaining this in the following 5-minute video;
In Summary, I think it’s important to do your own research and draw your own conclusion about the long term risks of ketosis. For some people, a ketogenic diet may be a necessity given their health situation. For those of us who do not suffer from such health conditions I would present the question ‘why do you want to follow a strict ketogenic diet for an extended period’, and then follow this up with ‘are the potential risks and sacrifices worth the benefits?’
Personally, I enjoy my milk and sweet potato too much to follow a long term ketogenic diet (though I have experimented with a 12-week strict ketogenic diet – something which I won’t be doing again. More on this at the end of this article).
Also, it’s important to remember that just because something may be SAFE (and to reiterate, I’m not saying a long term ketogenic diet is safe), it doesn’t mean it’s good for you or beneficial. Running Marathons could be considered safe (especially if it’s on a closed race circuit), but does this mean it’s good for you? Or should you be out running marathons every day?
Ketosis and it’s (negative) impact on thyroid function is a hotly debated topic. As with many things in the diet world, it really boils down to self-experimentation. Just because something works for one person, doesn’t mean it won’t work for another.
Below I have listed numerous opinions and data on the link between thyroid health and ketosis. Please read through all resources and draw your own opinion. Or even better, do an n=1 experiment, test your thyroid markers while on a normal diet, then follow a ketogenic diet for a few weeks and retest your thyroid markers to see what changed..
Do Low-Carb Diets Lower Thyroid Function? Let's Ask The Experts!
First up we have a panel hosted by Jimmy Moore.
Next we have an article by Precision Nutrition who look at a few studies on thyroid health and low carb dieting. In their article they remark ‘When calories and carbs are too low, your T3 levels drop.’
In counter to the Precision Nutrition article, you have an article by Ketotic.org who claim that Low T3 is not hypothyroid and maybe be beneficial for weight loss and increased longevity. This article can be read HERE.
There are also some great anecdotal articles on ketosis and thyroid health on the BjjCaveman.com website. I recommend reading the following:
Again, this is a controversial subject with strong arguments from both sides. I strongly believe that you need to do your own research on this subject and if you decide to follow a ketogenic diet, track your progress and bloods.
Finally, if you do have a pre-existing thyroid condition, then it may be wise to steer clear of a ketogenic diet. Should you still desire to follow a ketogenic diet, then at least work in regular carb refeeds a la Carb Backloading style. Read THIS article for more on the importance of carb refeeds.
There is no correct ‘number’ when it comes to finding the perfect ‘ketogenic diet’. The short answer is ‘it depends’. And the best way to find the perfect diet for you is to test (more on this below). However, here are a few starting points.
Jimmy Moore from Keto Clarity states:
'...effective strategies for increasing ketone production may come from the traditional teachings of the Ketogenic Diet, which calls for a fat to protein and carbohydrate ratio of four to one. First, the protein requirement is determined: 1 gram of protein per kilogram of body weight.
Then, add in 10 to 15 grams of carbohydrate. The rest of the diet is comprised of fat. So if a child weighs 44 pounds (20 kilograms), the daily protein intake would be 20 grams and carbohydrate intake would be 10 grams, for a total of 30 grams that are not fat.'
Dr Peter Attia, from The Eating Academy, uses a similar formula. He explains his forumala in detail in his article Ketones and Carbohydrates: Can they co-exist?
The “rule of thumb” for NK is that caloric intake is determined as follows (this excludes a subset of ketogenic diets known as calorie-restricted KD which, as the name suggests, is specifically restricted in calories):
Carbohydrate (total, not “net”): less than 50 gm/day, but ideally closer to 30 gm/day
Protein: up to 1 to 1.5 gm/kg, but ideally below about 120 gm/day
Fat: to satiety
Therefore the macronutrient breakdown for an individual will depend on their body weight.
Dr Attia uses a great graphic to show this difference:
Let me illustrate what this looks like for Joe (left), Jane (middle), and Jeff (right — an example of a calorie restricted KD), three hypothetical people in NK — but each with different caloric requirements.
Finally, Dr Attia adds:
A Note on carbs – I go with total not net, as I have found that fiber does seem to have a small impact on ketosis.
If you still need help working out your exact macronutrient breakdown then be sure to check out the Keto-Calculator over at - http://keto-calculator.ankerl.com/
I recommend going back and reading the section on Thyroid and Ketosis and Long Term Safety as I cover this subject in great detail in those sections. But to answer this question the answer really depends on what you mean by ‘Do You Need Carbs’.
Do you need carbs to survive the day? No. Anyone who has fasted more than 24 hours can prove this (I have gone 72 hours without food and I still am here to tell the tell – read more here).
Do you need carbs to train? No. Again this is an anecdote only, but I have done numerous training sessions in a carb deprived state. Heck some of my best training sessions where done in a fasted, carb deprived state. And there are a lot of endurance athletes who are using a ultra-low carb/ketogenic diet and putting up some great times (more on this below).
Dr Peter Attia states that even those who follow a strict ketogenic diet – eating zero carbohydrates – still has “still has about 50-70% of a normal glycogen level, as demonstrated by muscle biopsies in such subjects.”
So instead of asking ‘Do you need Carbs’, you should ask ‘Do I need carbs to THRIVE?” And this is where the answer gets tricky.
Even though endurance athletes can train in a carb depleted state, they will generally consume carbohydrates in the lead up to a race (the athlete is seeking to increase the ability to run off fats by training in a carb depleted state, then benefiting from both fats AND carbs come race day). Likewise, with the brain, even though the brain can function off ketones, does it mean it’s the best state for brain function?
Fat. Lots of it!
A few popular food choices include:
There are many meal plans on the web for ketogenic diets. So I won't go into too much detail here, instead I have listed a few ‘typical days’ below to give you a rough idea:
For some great recipe ideas be sure to check out the book Keto Clarity, or these two recipe books:
This following section includes foods that you should avoid if you want to remain in ketosis. I am not claiming that the following foods & supplements are unhealthy or bad in anyway, I am simply providing a list of foods/supplements that should be kept to a minimum if you goal is a high blood ketone reading.
Simple, avoid consumption of all sugars if your goal is strict keto. The resulting insulin spike will knock you right out of ketosis. This means you should limit foods such as fruit, honey, syrups, all sugar, fruit juice, soda, milk etc.
You may find a tiny amount here and there is ok (i.e., 2g of sugar with a meal full of fat may be ok). But if you are starting out I would recommend cutting all sugar from your diet, and most importantly avoiding any sugar consumption on an empty stomach. For best results track your ketone levels before and after meals to see the impact the food has on your ketone levels.
This includes root vegetables such as potato, pumpkin and all grains (and grain derived foods such as bread and flours). These may not cause the same blood sugar spike that pure glucose does, but the blood sugar increase will knock you out of ketosis, especially if these foods are consumed on an empty stomach and or without fats.
This is something that you will have to test as the impact of artificial sweeteners tends to vary between individuals. Some artificial sweeteners cause a blood sugar spike – which can knock you out of ketosis.
My recommendation is simple: Avoid all artificial sweeteners and if you want to use them, then test your ketone levels before and after to see the impact they have on you.
Glucogenic Amino Acids
There are a few supplements that I would recommend avoiding if you want to remain in ketosis. Two of the big ones are Glutamine and Alanine.
This from Wikipedia:
A glucogenic amino acid is an amino acid that can be converted into glucose through gluconeogenesis. This is in contrast to the ketogenic amino acids, which are converted into ketone bodies.
The production of glucose from glucogenic amino acids involves these amino acids being converted to alpha keto acids and then to glucose, with both processes occurring in the liver. This mechanism predominates during catabolysis, rising as fasting and starvation increase in severity.
In humans, the glucogenic amino acids are:
For instance a 10g serve of glutamine dropped my blood ketone level from 2.8 to 0.4 mmol.
This comment from zerocarbzen:
This may have been mentioned, I haven’t checked all comments, but glutamine causes gluconeogenesis so that may explain why it affects Ketosis. Whenever I took a glutamine powder supplement for gut healing, I noticed I would “feel” less Ketogenic and I knew it was affecting me adversely. Glycine (which is also in bone broth) also has this effect I believe. Apparently some amino acids are just more easily converted to glucose.
You may find that other pure or high dose amino acid supplements (or foods) can have the same effect. Some examples would include:
Also, like glutamine, Alanine can have a profound impact on ketosis. One study titled - The effects of alanine, glucose and starch ingestion on the ketosis produced by exercise and by starvation. Found that alanine supplementation knocked the participants out of ketosis as much as pure glucose did.
Note – not all amino acids are glucogenic. Leucine and Lysine for example are ketogenic.
As you can see from the above section, many amino acids are glucogenic – meaning they are easily converted into glucose. Glucose will then halt ketone production meaning your ketone levels will fall and you will be knocked out of ketosis. Amino acids are the building blocks of protein, thus protein itself can knock you out of ketosis.
This is probably one of the most understood notions of a true ketogenic diet (and the difference between a keto diet and a low carb diet). An optimal ketogenic diet will be low in carbohydrates AND protein. Many people who have experimented with low carb dieting simple reduce carbs and increase protein. A big reason behind this is due to the misconception that ‘’excess fat is bad – which is untrue, more on this HERE). However, excess protein can be converted to glucose (blood sugar) through a process called gluconeogenesis.
What this means for the ketogenic crowd is that your protein intake needs to be restricted (and even monitored) if you are seeking high blood ketone levels. How much protein is ‘excess’ and how much protein will knock you out of ketosis? The answer is ‘ it depends’.
Refer back to the section titled What’s a typical diet/macro breakdown for some rough calculations to get you started. Otherwise, simple test your blood ketones after a meal. If your ketone figure drops drastically, then you may have consumed too much protein in that particular meal.
One thing to remember here is that even if your calculated daily ‘keto approved’ protein allowance is (let’s say) 150g, that doesn’t mean you can eat 150g in one meal and still be in ketosis. You may find that you can’t eat more than 40g of protein at a time, otherwise you will drop out of ketosis. OR, you may find you can eat 50g of protein but you need a LOT of fat. Whereas a small serve of 15g of protein without fat might knock you out of ketosis.
Again, you need to test to find the impact of food on your body. But the most important takeaway here is ‘don’t overdo your protein consumption if you want to reach a state of ketosis’.
The simplest answer is ‘stop eating food’. But that’s not sustainable long term.
Otherwise you could:
Or use a combination of the above tactics. For example, one way to reach ketosis rapidly would be:
You can fast and the body will upregulate enzymes to help with fat oxidation in a matter of days. If you are seeking optimal sports performance however, it may take weeks or even months following a ketogenic diet before you will maximise the benefits from ketogenic diets. For more on this please see the following resources:
The best way to measure ketones is with a blood glucose meter. I personally use the Abbott Freestyle Optium Neo ketone meter. You can buy this online for around $20-50. Strips cost anything from $1 to $5 depending on what specials you can find.
To measure your ketone levels, you simply prick your finger with the lancet that comes with the Freestyle device, and test your blood using a ketone strip. Wait a few seconds and your ketone level will show on the screen. A regarding above 0.5mmol generally indicates that you’re in a state of ketosis.
Watch the following video for a full demo:
When you are in a state of ketosis, the body turns fatty acids into ketones - these appear as beta-hydroxybutyrate in the blood. Measuring blood ketones is regarded as the gold standard and most accurate way to track ketone levels. Testing this way can be expensive, its can cost up to $3 a strip, so if you're testing multiple times a day it can get pricey.
Fortunately a new way to test ketosis has been developed - and that is by measuring acetone levels in the breath. This is rather new technology but based on the reports I have seen it does look reasonably reliable. The testing process is simple, you use a device like that made by Ketonix, you breathe into it, wait a minute or so and it will give you a color indicating the state of ketosis you are in. However, there are numerous downsides:
I personally haven't used one of these devices, I thought about buying one, but instead put my money towards more blood strips. I like seeing the exact mmol/L figure - and at the moment only blood tests show this data - so until this changes I'll probably stick to (and recommend) pricking your finger when it comes to checking ketone levels.
NB - for a full comparison on blood vs breath check out this page.
For this section I am going to reference BJJCaveman.
In his article - The Basics of Nutritional Ketosis he covers this topic very succinctly:
The best time is first thing in the morning while fasting. This will give you the most accurate reading.
Volek and Phinney describe a diurnal variation in ketone production, with the lowest amount in the AM. So if you’re in the zone in the morning, then you should be for the rest of the day, since that will be your lowest reading.
In my experience I’ve become distrustful of testing later in the day because of the potential effect of my meals. Food can still be absorbed 6 hours after you’ve swallowed it.
The reason you test is to know whether your body is producing ketones. You don’t want any ketones coming from something you’ve eaten to screw up your numbers and give you a false impression as to what’s going on.
And you can see more of his thoughts on this topic HERE.
If you are aware of particular foods or supplements that knock you out of ketosis, please leave a comment below and I’ll add it to this list.
It really depends. It depends on:
For most people, 1-3 days after a big carb meal you will be back in ketosis (assuming you are back to following a ketogenic diet of course). The use of mct oil, ketone supplements and fasting can all help speed this process up.
Lyle McDonald, in his book "The Ketogenic Diet", states the following:
The major determinant of whether the liver will produce ketone bodies is the amount of liver glycogen present (8). The primary role of liver glycogen is to maintain normal blood glucose levels. When dietary carbohydrates are removed from the diet and blood glucose falls, glucagon signals the liver to break down its glycogen stores to glucose which is released into the bloodstream. After approximately 12-16 hours, depending on activity, liver glycogen is almost completely depleted. At this time, ketogenesis increases rapidly. In fact, after liver glycogen is depleted, the availability of FFA will determine the rate of ketone production. (12)
So if you do binge eat some carbs and you want to return to ketosis asap, it might be wise to:
Finally, track your ketone levels and see what works best for you. You may find that a 24 hour fast brings your ketone levels back up to where you want it, or you may find a ton of mct oil works better. Experiment.
It is very important to increase your salt consumption when on a ketogenic diet.
This from Ben Greenfield:
First, ketones naturally act as a diuretic, so you lose salt, potassium, calcium and magnesium, and it is generally encouraged to increase sodium intake with ketones.
When you restrict carbs, the kidneys excrete a lot of sodium. Not replacing this sodium can leave you feeling light headed. I recommend having a big glass of spring water with ½ teaspoon of Celtic sea salt twice a day (first thing in the morning and midafternoon are two times that work well). A long with this, make sure you use a lot of salt on your meals.
A lot of people who use ketogenic diets will include a regular (i.e. weekly) carb refeed meal. There are various reasons behind doing this. If you are doing a lot of glycolic based training, then the carb refeed can help bump up muscle glycogen levels and in turn boost performance. Others use these refeeds as a way to keep their thyroid health in check, and finally some people use these refeeds as a ‘cheat day’ – so that they can still enjoy the pleasures from carbohydrates!
Personally, I think it is wise to include a regular carb meal in your diet if you are going to follow a ketogenic diet. Long term ketogenic diets do seem to downregulate your thyroid and metabolism, and a weekly carb meal (or carb day) can help avoid this. The Carb Nite diet by J. Kiefer is a good example of this. And BJJCaveman posted his labs showing how a weekly carb meal helped his thyroid HERE.
Kiefers Carb Nite book, and his Carb Backloading books go into a lot more detail behind the importance of regular carb refeeds, and also the optimal time to eat carbs in regards to fat loss and sports performance.
Finally, if you are nervous about a carb refeed, but understand the importance of doing so, look at using bitter melon extract supplements with your carb meal to help clear the glucose from your blood (note, if you are ordering supplements from Iherb.com use promo code BHS654 at checkout for a discount.)
At the time of writing this article, this is an area that I don’t have much experience with outside of MCT supplementation. For that reason, I will refer to individuals who DO have a lot experience with ketone supplementation.
Before that though, I do want to touch on MCT oil and it’s impact on ketone levels. MCT – or Medium Chain Triglyceride – are fatty acids that bypass the liver – and become quick energy for the brain and muscles. As they are a fat based energy source (and not a carbohydrate) they are quickly converted into ketones. This means MCT oil is a great way to boost ketone levels in the body.
Now to look at exogenous ketone supplementation.
For a bit of an overview on exogenous ketones, be sure to have a read of this article – Instant Ketosis – by Patrick Arnold.
Next, we look at the work of Peter Attia. In his article My Experience With Exogenous Ketones he performs an experiment looking at the effectiveness of ketone supplementation. Be sure to read the article for all the details, but in summary he found:
“Animal models (e.g., using rat hearts) and unpublished case reports in elite athletes suggest supplemented BHB (ketone salts) produces more ATP per unit carbon and per unit oxygen consumed than glycogen and FFA. This appears to have been the case in my anecdotal exercise.
The energy necessary to perform the mechanical work did not appear to change much between tests, though the amount of oxygen utilization and fat oxidation did go down measurably. The latter finding is not surprising since the body was not sitting on an abundant and available source of BHB—there was less need to make BHB “the old fashioned way.”
…. Finally, these compounds seemed to have a profound impact on my appetite (they produced a strong tendency towards appetite suppression). I think there are at least two good explanations for this, which I plan to write about in a dedicated post. This particular topic—appetite regulation—is too interesting to warrant anything less.”
However, there may be a down side to ketone supplementation. THIS T-Nation article concludes:
“Ketones may be a better source of fuel than glucose, and a far better beverage than Fruitopia, but it's a question of whether or not you can spare the extra fuel….
And if you know your science, then what that extra dose of ketones leads to is glycation, oxidation, and conversion to fat for the metabolically deranged majority, and elevated insulin because of excess energy in the bloodstream.”
While over at Calories Proper, Bill Lagakos reviews some studies that look at ketone supplements. His conclusion, context is everything:
So, throwing some ketone monoesters into your pre-workout drink might improve net physical performance, depending on your sport. But then there’s that other issue, that elevated ketones and glucose = no bueno. Acute physical performance boost at the expense of healthspan? Idk.
A later article by Bill on Ketone supplements supported his original belief :
My two cents: I wouldn’t take ketone supps if not on some sort of low(ish) carb diet because the idea of high levels of BOTH fuels (ie, ketones AND glucose) doesn’t seem physiologically appropriate… more like a recipe for disaster, and by “disaster,” I mean “out-of-control production of Reactive Oxygen Species” — this might not matter if you’re an athlete looking for a quick performance boost, because the fuels are going to be cleared rather quickly… not so much if you’re a desk jockey.
For more on this topic (and there is a LOT more out there) be sure to check out the following pages:
This is another big topic. So big in fact that there are podcasts and websites dedicated to it.
If you are looking at eating a ketogenic diet for improved endurance performance, then let me say that – yes there is some solid evidence coming out that at least a lower carb, higher fat diet can improve aerobic capacity and if this is something you want to explore further then check out:
There are many health benefits of fasting. I cover this in detail in my article Fasting: How Skipping Meals Can Burn Fat & Increase Lifespan.
Fasting is often used by individuals on a ketogenic diet. Why? Because when you fast, your body needs to derive energy from the stored body fat and stored liver glycogen. During this time the body will increase production of ketones.
Fasting = Ketosis.
And yes this means that even a high carb sugar burner may reach a very mild state of ketosis after a night without food. Fasting is an effective way to enter a state of ketosis. As without ketones we would not be able to survive any extended period without food.
For more on this topic please see:
To see what happens to ones Ketone levels on a 5 day water fast be sure to check out this article:
Finally, a word of caution. If you plan on using intermittent fasting to help keep you in ketosis, remember that a large consumption of carbs and or protein in one meal can knock you out of ketosis. So sometimes it is better to shorten your fast period and extend your feeding window to stay in ketosis but still benefit from fasting.
Before starting a ketogenic diet, it is important that you consult a medical professional. Also, I highly recommend reading my section on Ketogenic Safety and the section on Thyroid.
Along with the concerns addressed in those sections, I also list a few other potential ‘downsides’ of ketosis.
Peter Attia states that kidney stones are possible as a result of a ketogenic diet:
“…it’s certainly possible due to the changes in how the kidney process minerals. For this reason I supplement with calcium carbonate.”
Particularly if bad fats are eaten. This from Ben Greenfield:
‘Let’s say you decide you’re going to get into ketosis by eating boatloads of grass-fed butter, peanut butter, almond butter, animal meats, and oils, and you aren’t very selective in the quality of those fats.
That’s a definite shortcut to throwing your triglycerides through the roof.
And not only are high levels of circulating triglycerides a good way to get fat fast, but studies have consistently linked high triglyceride levels with heart disease, heart attacks and stroke. Fructose is one quick way to elevate triglycerides, but this really doesn’t seem to be an issue with high-fat, low-carbers.
However, vegetable oils and butter and animal fats and nuts and seeds can also significantly raise triglycerides. One big issue here is that if these oils and fats have been exposed to high amounts of temperature and processing, triglycerides are getting dumped into your body chock full of free radicals.
So if your high-fat diet includes a high amount of roasted seeds or roasted nuts, nut butters, heated oils such as heated coconut oil or heated extra virgin olive oil, barbecued meats or meats cooked at very high temperatures, then your triglyceride count is going to go up. You should have triglycerides that are less than 150mg/dL, and a triglyceride to HDL ratio that is no more than 4:1, and in most of the healthiest people I’ve worked with, triglycerides are under 100 and the triglyceride to HDL ratio is less than 2:1. If your ratio is whacked, your ketogenic diet isn’t doing you any favors.’
Eating a keto diet requires a lot of control over your diet. Sure society is starting to offer vegetarian options, low fat, low carb and gluten free choices, but eating ‘keto’ out at restaurants or cafes can be tough.
Likewise, with eating at a friend’s place or when grabbing a quick bite to eat on the road. Sure you can ask for extra butter, or grab a packet of macadamia nuts here and there, but if you eat out often, a ketogenic diet is going to be tough.
This is a decision that you need to make. However, if you want my opinion (and it's just that, an opinion. I'm not a doc nor do I give out medical advice, always check with your doctor before undergoing any radical dietary changes such as a ketogenic diet), then here goes:
Do I still follow a ketogenic diet? Not anymore. I was strict keto for 12 weeks – enough time to experiment and learn about it. I did enjoy parts (lots of fat!) but I don’t see it as a sustainable way of eating, nor did I benefit from it health or sports performance wise (more on this in an upcoming article). But, I was following a strict keto diet – sans carbs. I think if I were to follow a ketogenic diet AND incorporate a regular carb refeed then the results may be different.
Podcasts & Summits:
My goal with this article was to make the most comprehensive, single page resource on ketogenic diets. I wanted to create an article that I wish I had read prior to doing my own ketogenic experiment.
If I have missed something, or if you have read this guide and still have questions, PLEASE post them below or email them to me and I’ll be sure to answer them and update this resource.
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