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The Ultimate Guide to Ketosis

Last updated: May 10, 2020 at 7:44PM | - Published on: Nov 4, 2018

Written by Raphael Sirtoli, Msc

Scientifically Reviewed by Sarah Neidler, PhD

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What is ketosis?

Ketosis is a metabolic state. Think of being in or out of ketosis like the settings in a hybrid car; you can rely on gas or electricity to different degrees. In ketosis we rely on fat instead of carbs for energy and do so to such an extent that we start making ketones from fat.

These ketones can be used to fuel us and send many important signals to our cells. There are three different kinds of ketones: Acetoacetate (AcAc), β-Hydroxybutyrate (BhB) and Acetone.

AcAc is created first, and it can easily be converted into BhB. Technically, BhB isn’t a ketone. It’s close enough to one we still call it a ketone. Acetone is spontaneously created as a side product of AcAc. Acetone cannot be used as a source of energy but can be measured in the breath, serving as a useful but imperfect measurement of ketosis.

To know more about how to measure the depth of your ketosis check out our guide about how to measure ketone levels.

Your body is always producing a very low level of ketones, irrespective of your diet. You start producing more of them when following a diet that’s high in fat and low in carbs. For a weight stable person following a well-formulated ketogenic diet, that means about 5-10% of calories from carbs, 70-80% from fat and 20-30% from protein.

This excludes everything that is high in carbs, such as grains, potatoes, and sweets – or at the very least allows only tiny, infrequent portions of them. Low-carb vegetables such as kale, broccoli, salad, and other leafy greens can be eaten without restriction.

Nuts are also a keto friendly food given their high fat content. Macadamia nuts and pecans are very low in carbs and high in fat. Cashews on the other hand are relatively higher in carbs but still quite fatty.

Vegetables such as sweet peppers and tomatoes are ‘allowed’ but have a bit more carbs so may need to be moderated for those who are highly insulin resistant. The more insulin resistant you are, the harder is it to get into ketosis.

All meats, fish, eggs, birds and seafood are part of a well-formulated ketogenic diet. You’re encouraged to eat the fattier cuts and offal (e.g. liver). Liver is by far the most nutrient dense food.

While being in ketosis, you efficiently burn fat and use ketones as fuel. Ketosis is, therefore, a metabolic state that allows you to maximize fat burning. The amount of ketone production does however not correlate to fat loss, despite it facilitating fat loss for those who have extra fat to lose. Normalizing appetite is a big reason why.


Is ketosis a natural state?

Yes, it is. Babies are born ketotic and stay so as long as they’re breastfed [1]. What could be more natural for a baby than drinking its mother’s breast milk? As soon as babies or toddlers are given fruit puree, fruit juice and other nutrient poor sugar bombs they’re of course no longer in ketosis.

A small excursion regarding “healthy” fruits: Yes, it is correct that fruits contain meaningful amounts of vitamins. But eating whole fruit is very different from the processed versions that we feed our kids.

Pureeing or juicing fruit disrupts the natural architecture of the food which leads to poor metabolic responses – abnormally high insulin and blood sugar spikes. They also concentrate an awful lot of sugar, especially fructose.

Don’t prime your kid for metabolic syndrome and diabetes so keep them away from this type of processed ‘food’. Other it’s really like they’re eating sweet treats instead of a proper meal. Even most grown-ups are wise enough not to do this.

the difference between a carb addict and a fat burner is the way the body use fats as energy. A carb addict will use carbs for energy whereas a fat burner will burn body fats for energy

Back to the question of whether or not ketosis is a natural state. It’s fair to argue that the time after birth is a special period and might not be representative of the remaining developmental stages and adulthood. So what about adolescents and adults? Is ketosis a normal state for them?

For our ancestors, dipping in and out of ketosis was the norm. Starchy vegetables were energetically costly to obtain and weren’t available the whole year round. During winter or the ice-ages, the era in which we spent most of our evolving towards our present form, we had to rely on animals that are high-fat and have virtually no carbs.

And before the invention of supermarkets food was eaten for nourishment, not boredom. After eating nothing for 24 to 48 hours, most people enter ketosis [2]. This happens even faster when you are keto-adapted.

So assuming that food was not always available in abundance, it is more than likely that our ancestors were frequently in ketosis – even tropical island populations.

Populations living further north had much less edible vegetation available for gathering. Thankfully for us, animals that lived in these areas ate the vegetation inedible to us, effectively transforming it into fatty meat we could hunt and enjoy. These people most certainly relied on high levels of fat and protein, thus likely spending most of their time in ketosis.

ketosis support brain function. Your liver breakdown fats into molecule called ketones that burn fats for energy

How to get into ketosis?

When starting the ketogenic diet, most people would like to know how to quickly get into ketosis and how long this takes. There is a short answer: The stricter you restrict carbs (or total calories), the quicker you will be in ketosis.

Except for downing a ketone supplement, nothing beats fasting for getting you into ketosis ASAP. This means eating nothing and drinking only water. Fasting will get you into ketosis within 24-48 hours. The time to enter ketosis will get shorter over time because the better keto-adapted you are, the faster and easier you enter ketosis.

Fasting aside, restricting your carb intake to 20g per day is a good heuristic (loose rule) for entering ketosis. This will get you into ketosis within a few days or a week. The time it takes varies for individuals and depends on what you have eaten in the past, your body composition and how insulin sensitive you are.

20 g of carbs represents very little carby food. Even most keto foods contain a few carbs, and it simply adds up. Many people find it easier to abstain from dairy products, at least in the initial phase. Most dairy, even the full-fat versions, have around 4g carbs per 100 ml. By not eating dairy there are more carbs left for things like veggies and nuts.

After being in ketosis for a while, you may notice being able to tolerate a bit more carbs. If you so desire, gradually increase them and check for changes in your ketone levels and how you feel, look and perform (as Robb Wolf is fond of saying). You could start by eating dairy products again. But beware if you’re highly insulin resistant, milk and yogurt can have enough carbs to kick you out of ketosis.

So once you are in ketosis, can you stay in this metabolic state forever? Should that even be your goal? First of all, it is quite a challenge to stay in ketosis without interruption for a very long time. Eating out, your kids’ birthday cake and ‘hidden carbs’ are the usual suspects for leaving ketosis.

Ketosis is a sensitive state so as soon as you increase your carb intake above your carb tolerance, you’re out! You probably don’t want to continuously weigh and count your food for the rest of your life. So even if you stick to the approved list of ketogenic food, there is no guarantee that you will be in ketosis without interruption. That’s OK. Now if you’re in ketosis to manage cancer or epilepsy, that’s a different story obviously.

You may eat too much of your favorite moderate-carb vegetables from time to time (e.g. carrots, sweet peppers, parsnips) which may lower your ketones or outright kick you out of ketosis. Assuming that you are well keto-adapted, you will, however, quickly get into ketosis again.

The primary goals of the ketogenic diet for people like you and I, people living in modernity and eventually riddled with chronic disease, is to:

  • Lower insulin levels
  • Increase insulin sensitivity
  • Normalize body composition (% fat, % muscle)
  • Normalize blood pressure
  • Lower chronic inflammation
  • Improve immune function
  • Stabilize mood and mental function

Did you know?

Ketones aren’t just a form of energy, they’re powerful signaling molecules. They regulate the expression of genes and dampen inflammatory processes.

In 2015 it was found that the ketone we measure in our blood called beta-hydroxybutyrate (BhB) could ‘silence’ the NLRP3 inflammasome [2].

This inflammatory complex is involved in much of the pain and inflammation seen in rheumatoid arthritis, Alzheimer’s disease, obesity, atherosclerosis, type 2 diabetes and gout to name just a few.

This means ketones – whether produced by fasting, ketogenic diets or supplements – have actual and promising therapeutic potential.

There are no studies so far that have investigated the life-time effects of ketogenic diets in humans. The same can be said for most if not all diets, actually. They would be very difficult to realize.

The longest studies/follow-ups for ketogenic diets are about 10 years long and have shown it to be safe [3, 4, 5, 6]. Studies that carefully keep people in metabolic wards to strictly monitor food intake and biomarkers are always short because they are very costly and laborious. Moreover, most participants are not able or willing to participate for a long time in a study that supervises food intake around the clock. For these reasons, these kinds of studies are always of short duration, a few weeks maximum.

The alternative is to perform studies were participants undergo nutrition counseling, follow a specifically prescribed diet and self-report their food intake. The advantage is that these kinds of studies can be of long duration, so it is possible to study long-term effects – assuming people are actually eating what you’re telling them to. Of course, they don’t.

It’s well known that adherence to the prescribed diet is usually low and self-reported food intake is very unreliable. So there’s no way to guarantee that the participants strictly adhered to the diet. Because it requires a lot of discipline and planning to stay in ketosis for a long time without interruption, it won’t be possible to perform a long-term study that guarantees uninterrupted ketosis using old study methods. This may change soon with improved self-tracking devices.

What’s impossible in humans though can easily be done in animal studies. The downside is that animals are not identical to humans and it’s not always clear how relevant the results are.

You can find a mixed bag of studies in rodents; sometimes the ketogenic diet is amazing sometimes it’s terrible. The main reason why is because there are many kinds of ketogenic diets; what fats were used? how processed is the food and what was the method of processing? were these genetically manipulated mice or wild type? were they fed ad lib (to their hearts content), forced fed (hypercaloric) or had their calories restricted?

The only way to disentangle the results from these studies is to dive into complex study design, statistical methods and principles of physiology – a snooze fest for most of you. But if you do like that sort of stuff, check out our podcasts! 🙂

In conclusion, staying in ketosis for several years without interruption carries some risk, but relative to things like air pollution, chronic stress and a ‘normal’ diet (i.e. standard american diet), we at Nutrita consider these risks to be very, very minimal. So choose what you worry about wisely.

Ketosis is a normal metabolic state where your body CONVERTS fat into ENERGY thank to a little molecule called ketones. Well-formulated ketogenic diets provide you with the singular benefit of ketones as well as the complete range of essential micronutrients. There are three ways, the most accurate of which is blood beta-hydroxybutyrate (BHB). Breath acetone and urinary acetoacetate strips can also be useful estimates of ketosis.


Will exogenous ketones deepen ketosis?

To get into ketosis without supplementation, you have to keep your insulin levels low. Supplementing with exogenous ketones can help get you into ketosis [40]. However, you won’t have achieved the same beneficial physiological changes as you would have from a well-formulated ketogenic diet or fasting. This is why we at Nutrita don’t recommend exogenous ketones as a substitute for a well-formulated ketogenic diet.

Long-term, your body has a lot to gain from learning to efficiently burn fat and produce its own ketones. The only way to do this is by keeping your carb intake low, doing some sort of fasting or following a ketogenic diet.

Providing external ketones will not help you with this process specifically. However, exogenous ketones can boost your short-term energy levels which can be of interest in certain medical conditions or athletic performance. What they won’t do, and what’s often claimed, is that they will ‘boost fat burning’. That’s nonsense.

What is ketoacidosis?

Many people confuse ketosis with ketoacidosis. Ketoacidosis is the state where blood insulin is so low due to a ‘burned out’ pancreas that both glucose and ketones skyrocket to dangerous levels, leading to coma and death if nothing is done.

Ketoacidosis (or diabetic ketoacidosis) occurs in uncontrolled diabetes, not in nutritional ketosis. Uncontrolled diabetics are patients that have totally lost normal pancreatic function and aren’t dosing insulin accordingly. They’re also probably still on a standard American diabetes-inducing diet when this occurs.

Following a ketogenic diet with Nutrita

Starting a ketogenic diet as easy as it should be. No wonder, doctors aren’t really trained in nutrition and science journalism is in a terrible state.

You need the right distribution of carbs, protein and fat. You also need to understand how to apply these general principles to your situation. Nutrita helps you to follow a well-formulated ketogenic diet that is nutrient dense, tasty, complete in protein and truly filling.

The keto score helps you quickly get into ketosis and stay there. The insulin index ensures you avoid the most insulinogenic junk-food items, often hidden in packaged foods, pushing you closer to diabesity with every bite. Jump right into with the app and get connected to many others who share the same questions you may have.

But is it recommended to stay in ketosis for let’s say several years without interruption? No one knows for sure, but the burden of proof is on those arguing that this natural metabolic state is inherently bad. Ketosis is as normal as not being in ketosis.


Nutritional ketosis is a normal metabolic state.

More and more modern science is supporting the idea of at least dipping in and out of the state for general health, whether that’s via intermittent and longer fasts or simply a well-formulated ketogenic diet. Sports science is also starting to support the notion that ketogenic diets can adequately support a range of athletic activities.

The question of whether or not it’s optimal for certain sports is still an open question.

Diabetic ketoacidosis is still confused for nutritional ketosis, a mistake akin to confusing drinking water with drowning.

Going from a standard-American diet to a well-formulated low-carb or ketogenic diet is a health upgrade. However, it usually comes with unpleasant but temporary symptoms of carbohydrate withdrawal, also known as the keto flu. This is easily addressed by using Nutrita to properly follow a ketogenic diet or simply by familiarizing yourself with basic electrolyte management.

Ketogenic diets are also being tested as therapies for a range of modern chronic diseases like Alzheimer’s, cancer and diabetes with extremely promising results. Although they’re not a panacea, it’s worth keeping an eye on given the positive trend.

Written by Raphael Sirtoli, MSc

Raphael Sirtoli has an MSc in Molecular Biology and is a PhD candidate in Neuroscience at the Behavioral n’ Molecular Lab in Portugal. His understanding of metabolism, nutrition and clinical medicine is the base upon which Nutrita’s knowledge derives from. He loves open scientific debate, Crossfit, football, hiking, and cold water immersion.

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