Ketosis is a word that gets tossed around a lot within the Paleo community – to some, it’s a magical weight-loss formula, to others, it’s a way of life, and to others it’s just asking for adrenal fatigue. But understanding what ketosis really is (not just what it does), and the physical causes and consequences of a fat-fueled metabolism can help you make an informed decision about the best diet for your particular lifestyle, ketogenic or not.
Ketosis is essentially a metabolic state in which the body primarily relies on fat for energy. Biologically, the human body is a very adaptable machine that can run on a variety of different fuels, but on a carb-heavy Western diet, the primary source of energy is glucose. If glucose is available, the body will use it first, since it’s the quickest to metabolize. So on the standard American diet, your metabolism will be primarily geared towards burning carbohydrates (glucose) for fuel.
In ketosis, it's just the opposite: the body primarily relies on ketones, rather than glucose. To understand how this works, it’s important to understand that some organs in the body (especially the brain) require a base amount of glucose to keep functioning. If your brain doesn’t get any glucose, you’ll die. But this doesn’t necessarily mean that you need glucose in the diet – your body is perfectly capable of meeting its glucose needs during an extended fast, a period of famine, or a long stretch of very minimal carbohydrate intake.
There are two different ways to make this happen. First, you could break down the protein in your muscles and use that as fuel for your brain and liver. This isn’t ideal from an evolutionary standpoint though – when you’re experiencing a period of food shortage, you need to be strong and fast, not getting continually weaker. Fortunately, you also have another source of glucose manufacture: ketone bodies.
Ketone bodies are a type of fatty acid – they’re basically byproducts of the process that converts protein to glucose in the liver. Ketone bodies fill part of your brain’s need for glucose (so you don’t have to break down as much of your muscle mass), and they also power all your other major organs. If you eat a diet very low in carbohydrates and protein (which forces your body to look elsewhere for glucose), your entire metabolism will switch over to using ketones as fuel instead – this is called ketosis.
Ketosis and Ketoacidosis
In any discussion of ketosis it’s important not to confuse ketosis with ketoacidosis. Confusion over the similar names is one reason why many people think a ketogenic diet is dangerous, but in reality, they're two lookalike words for two completely different things. Ketosis is when everything's going fine; you're just running on fat rather than glucose. But ketoacidosis is a very dangerous metabolic state that most commonly occurs in Type 1 diabetics. In Type 1 diabetes, the pancreas does not produce enough insulin, so even if a Type 1 diabetic eats a whole plate of pasta, he won’t be able to digest and use the glucose for energy. He’s eating enough food, but his body is starving. As an alternative, his body starts to burn fat to meet its basic fuel needs.
This would be perfectly fine, except that one of the most important hormones for regulating ketone production is insulin. Since Type 1 diabetics don’t produce enough insulin to regulate the production of ketone bodies, burning fat for fuel involves the uncontrolled production of far too many ketone bodies. Remember that ketone bodies are fatty acids (and thus acidic); producing an uncontrolled amount of ketones upsets the balance between acid and base substances in the body and causes inflammation, dehydration, and swelling in the brain tissue, which can be fatal if left untreated.
Obviously, ketoacidosis is not a condition anyone wants to deal with, no matter what the potential benefits might be. But it simply isn’t a concern for most people, because when anyone but a diabetic relies on fat for fuel, they can count on insulin to keep ketone production to healthy levels. Even if you find that ketosis is not quite right for you for other reasons, there’s no need to avoid it for fear of going into ketoacidosis instead.
Understanding the difference between ketosis and ketoacidosis is one thing, but that still doesn’t explain why anyone would actually want to be in ketosis. If it’s is so metabolically similar to starvation, can it really be beneficial?
For some people, yes. The most common reason for attempting to go into ketosis is to lose weight. In several studies, a ketogenic diet has outperformed either a typical low-carb diet or a calorie-restricted diet for weight loss. When the body is already running on fat for fuel, it’s metabolically easy to burn the stored fat already on the body as well as the fat obtained through the diet. Ketosis can even help heal some of the longer-term damage brought on by the Western diet: in obese people who are insulin resistant, a ketogenic diet can help restore insulin sensitivity and restore regular metabolic function.
In one particularly interesting study, a group of 31 obese subjects ate a diet very similar to Paleo. Nicknamed the “Spanish Ketogenic Mediterranean Diet,” it consisted of fish as the main dietary protein, olive oil as the main fat, and lots of non-starchy vegetables. Subjects also drank a moderate amount of red wine daily. In contrast to most Atkins-type diets (which rely on processed low-carb meal replacements), this is a diet extremely high in healthy fats and micronutrients, and low in toxins. The results were impressive: as well as losing weight, the subjects also enjoyed improved blood pressure numbers, fasting glucose levels, and cholesterol profiles. In 12 weeks, a diet that could easily be described as “Paleo” had dramatically improved several important health markers.
As an added weight loss benefit, ketosis also has a well-documented appetite suppressing effect, due in part to its effect on blood sugar levels. A ketogenic diet minimizes swings in blood sugar, so you don’t get exhausted and cranky when you haven’t eaten for a few hours. This makes it easier to stay within a reasonable amount of food every day, even without conscious calorie restriction (which is generally a bad idea).
As well as an effective weight-loss diet, ketosis also shows promise as a therapeutic diet for various neurological disorders. Since the 1920s, it's been a scientifically acknowledged treatment for at least one health condition: epilepsy. Epilepsy is a brain disorder that causes repeated seizures; some people are born epileptic, and others develop the disorder due to injury, infections, or other trauma to the brain. Scientists aren't sure why ketosis is so beneficial for epileptic patients – a variety of explanations have been suggested but none have ever been proven. However, the undeniable fact is that ketosis is safe and effective therapy for epilepsy, especially in children.
Building on the work of doctors treating epileptic patients, some studies have indicated potential benefits of ketosis for neurodegenerative diseases like Parkinson’s and Alzheimer’s Some patients have successfully used a ketogenic diet to treat migraines, and researchers found that it may also be of some help in treating brain tumors. In general, ketosis seems to be potentially therapeutic for a wide range of brain and neurological disorders. This probably has something to do with the metabolic shift from glucose to ketones in the brain, although the specific reasons are still under investigation. But it’s a very interesting avenue of research, and definitely worth investigating if you or someone close to you is suffering from neurological symptoms.
To sum up the documented health benefits of a ketogenic diet, it seems that ketosis is most clearly useful for people with severe health problems like obesity or epilepsy. For these conditions, ketosis is a relatively safe and effective treatment – certainly better than spending the rest of your life on a cocktail of seizure medications or suffering all the side effects of uncontrolled diabetes. But healthy people who aren’t at risk from one of these conditions might want to think twice about adopting a ketogenic diet, because ketosis doesn’t come without its own set of risks.
Risks and Drawbacks of Ketosis
The benefits of ketosis are undeniable, but on the other hand, it also has certain risks. For a few people, it's not even an option – anyone with Pyruvate Carboxylase Deficiency, porphyria, and some other metabolic disorders (especially disorders that prevent the person from metabolizing fat properly) should steer well clear of ketosis. These diseases are rare, though– more common are conditions that don’t rule out the use of a ketogenic diet but do require extra care and attention to make it safe.
Type 1 diabetics, for example, need to be very careful when attempting a ketogenic diet. At first it might seem obvious that Type 1 diabetics should avoid ketosis entirely, for fear of slipping into ketoacidosis instead, but in fact a ketogenic diet can be safe for Type 1 diabetics who are also taking insulin replacement. The triggering factor for ketoacidosis is a lack of insulin, so insulin replacement hormones can make ketosis workable, even if it's not entirely risk-free. In children with both epilepsy and diabetes, doctors experimenting with a ketogenic diet for epilepsy have had significant success in balancing both conditions: ketosis to eliminate epilepsy symptoms, and insulin replacement to control the production of ketone bodies. But this is still somewhat of an experimental therapy, and there are risks involved that non diabetics don’t have to consider. If you have Type 1 Diabetes and you’re interested in ketosis for any reason, the safest way to proceed is to talk to your doctor first.
Even for people who aren’t diabetic, a ketogenic diet can have certain drawbacks. Remember that ketosis is metabolically very similar to starvation. If you’re trying to increase your fertility or if you’re currently pregnant, ketosis can actually be counterproductive. Fertility is greatest when the body feels well-nourished (which makes perfect sense: evolutionarily, conceiving a child during a time of food scarcity could be very dangerous), so a very low carbohydrate diet that imitates starvation is not ideal for conception. Similarly, the healthiest nutritional state during pregnancy is being consistently well-nourished; ketosis can be dangerous for both mother and baby.
People who do a lot of high-intensity metabolic conditioning should also avoid ketosis. This kind of activity demands glucose for fuel. Your body can make its own glucose from fat and protein, but not at the rate that you need it for regular sprint workouts or Crossfit metcons. If you regularly try to push yourself through this kind of workout on a low-carb diet, you’ll burn through all your stored muscle glycogen right away, and then see your performance start to decrease. Instead of injuring your body and your metabolism by forcing yourself to keep going, match your carbs to your workouts and enjoy some sweet potato fries or another source of Paleo-friendly starches.
As well as risks that apply only to certain groups of people, some risks can also affect anyone on a ketogenic diet. Kidney stones are a well-known example: long periods of ketosis are a serious risk factor. Some studies also indicate a risk of bone density loss, a problem that could lead to osteoporosis or further complications down the road. Children on a ketogenic diet grow more slowly than their peers – not surprisingly, given that ketosis is so similar to starvation. A less serious but irritating side effect is constipation (possibly caused by the reduction of fiber-rich grains and carbohydrates in the diet). Other risks of very low carbohydrate diets in general include thyroid problems, Vitamin C deficiency, low energy, and mood disorders.
All of these side effects mean that it’s important to consider both sides of the issue if you’re thinking about a ketogenic diet. It might seem like a weight loss miracle diet, but it’s not without some attendant downsides.
How to Achieve Ketosis
If you do decide that a ketogenic diet might be useful for you, the good news is that it’s not very difficult to achieve. Sending your body into ketosis is actually quite simple – eat fat to supply most of your calories, limited protein, and no starchy carbohydrates (your carbohydrates should only come from non-starchy vegetables like salad greens). Most people will be able to achieve ketosis on a net carbohydrate intake (not counting fiber) of 50 grams or less per day – that’s the carbohydrates in 2.5 cups of blueberries, or 4 cups of chopped carrots. It’s also important to keep protein fairly low, because if your body has enough protein to turn into glucose, it won’t start producing ketones instead. Basically, the goal is to give your body no alternative but to burn ketones for fuel, so you need to severely restrict all energy sources other than fat.
To test for ketosis, you can actually buy commercial ketostix. These strips measure the ketones in your urine and change color accordingly. As you first enter ketosis, the strips will become quite a dark purple, indicating a high level of ketones in the urine. What confuses some people is that after a few weeks, the ketostix fade to a lighter shade of purple (fewer ketones in the urine) even though they haven’t altered their ketogenic diet.
This is actually normal and doesn’t indicate that you’ve gone out of ketosis. When you first enter ketosis, the sticks will be dark purple because you’re making too many ketones and excreting the ones you don’t need. As your body gets used to a ketogenic diet, it learns how to make only as many ketones as it needs. At this point, there aren’t a lot of extra ketones to be excreted, so there are fewer in your urine, and the strips don’t turn as dark of a color. If you kept flooding your body with unusable ketones for too long, you’d go into ketoacidosis, so it’s actually very healthy that you stop producing so many. As long as you keep up your ketogenic diet, you’ll stay in ketosis – there’s no need to worry that you’ve somehow done something wrong.
Minimizing the Risks of Ketosis
Even if you decide that the possible benefits of a ketogenic diet outweigh the risks, most people aren’t terribly thrilled at the thought of developing kidney stones or even a less severe problem like chronic constipation. Since any kind of ketogenic diet is really just a means to an end (ketosis), it follows that the best ketogenic diet is one that minimizes these risks – the diet that induces ketosis in the gentlest, least harmful way possible.
Certain dietary supplements can help give you a little more leeway on a ketogenic diet. The amino acids lysine and leucine support ketosis and allow a diet to include more protein without compromising ketosis. Short-chain fats like coconut oil are also very ketogenic because they signal the liver to make more ketones. These supplements are very useful because they make for more flexibility in the diet: achieving ketosis by carbohydrate and protein restriction alone is possible, but a slightly higher level of protein and carb intake, supplemented with these ketogenic foods, can help reduce side effects and make the diet safer for the long term. Supplementing with Vitamin D (which most of us should be doing anyway) can also help minimize the risk of bone density loss.
It’s also possible to choose a more moderate approach called a cyclic ketogenic diet. On this kind of plan, the goal is not to be in ketosis all the time, but rather to support a very flexible metabolism that can easily dip into and out of ketosis day by day. Cyclic ketogenic diets usually involve a few days of ketogenic eating, followed by a high-carbohydrate day or two approximately once a week. This lets you benefit from ketosis most of the time, while maintaining a much higher level of athletic performance and also enjoying much more dietary flexibility and variety. This kind of cyclic ketogenic diet is probably preferable to constant ketosis for most people, since it delivers the benefits of insulin sensitivity and weight management while minimizing many of the risks of long-term ketogenic dieting.
Conclusion: Is Ketosis for You?
The answer to that question is, of course, “it depends.” Since we have evidence of hunter-gatherer tribes eating such a wide variety of macronutrient ratios, it seems clear that human beings are not evolutionarily designed to be in ketosis all the time; it’s more likely that we have a very flexible metabolic structure that can function quite well burning either ketones or glucose for fuel.
Thus, if you’re pregnant, extremely athletic, or have another contraindicating factor, or if you do just fine on a moderate-carb diet and see no reason to change, then there’s no reason to try for ketosis. If you're interested in the potential benefits but don’t want to go all the way, a cyclic ketogenic diet might be a better choice – it lets you experiment with ketosis without risking the side effects of a long-term very low carb diet. On the other hand, if you feel better on a fat-burning metabolism, want to lose weight, or you’re trying to manage a neurological disease, there’s no reason to worry that ketosis is somehow harmful or unnatural.
Realistically, a long-term ketogenic diet can be thought of more as a therapeutic intervention than a goal that everyone should be attempting to reach. For patients who suffer from obesity or neurological disorders like epilepsy, it can be a safe and effective treatment, but that doesn’t mean that perfectly healthy people should necessarily adopt it. Glasses are also a safe and effective treatment for poor vision, but that doesn’t mean that people who can see perfectly well already should all go out and get them. Think of a ketogenic diet as one of several equally legitimate options, and choose the way of eating that works best for you.
Want a more visual glance about ketosis and the keto diet? Have a look at our infographic here.