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Ketosis has become an extremely popular topic as of late, and it has received its share of praise and criticism. Is it healthy or harmful? And if it is beneficial, can it be for everyone?

In this article, we'll provide you with all the information you need about this metabolic condition: its benefits, potential risks, and tips for successfully entering and staying in ketosis.


What is Ketosis?

Ketosis is a metabolic state in which the body uses fat and ketones rather than glucose (sugar) as its main fuel source. 

Glucose is stored in the liver and released according to energy needs. However, after carbohydrate intake has been extremely low for a day or two, these glucose stores become depleted. Your liver can make some glucose from the amino acids in the proteins you eat, through a process known as gluconeogenesis, but not enough to meet all of your brain's needs, which requires a constant supply of fuel.

Fortunately, ketosis can provide you, and especially your brain, with an alternative source of energy. In ketosis, your body produces ketones at an accelerated rate. Ketones, or ketone bodies, are made by your liver from the fat you eat and your own body fat. The three ketone bodies are beta-hydroxybutyrate (BHB), acetoacetate and acetone (although technically acetone is a breakdown product of acetoacetate).

The liver regularly produces ketones even when you eat a high carbohydrate diet. This happens mostly during the night while you sleep, but only in small amounts. However, when glucose and insulin levels drop, as in the case of a high carbohydrate diet, the liver increases the production of ketones to provide energy for the brain. Once your blood ketone level reaches a certain threshold, you are considered to be in nutritional ketosis.

Does the brain need carbohydrates?

There is a long-standing but incorrect belief that carbohydrates are necessary for the brain to function properly. In fact, if you ask some dietitians how many carbohydrates you should eat, they'll likely answer that you need a minimum of 130 grams a day to ensure your brain has a constant supply of glucose. However, this is not entirely true. In fact, your brain will remain healthy and functional even if you eat no carbohydrates at all.

While it's true that your brain has high energy needs and requires some glucose, when you're in ketosis it's ketones that provide a good portion of its fuel. Also, fortunately, your liver will always produce the small amount of glucose your brain needs, even under conditions of complete starvation.

For example, this system allowed our hunter-gatherer ancestors to go for long periods without eating because they always had access to one source of fuel: stored body fat. This condition therefore has no adverse effects on brain function. Conversely, many people have reported feeling mentally sharper when in ketosis.8

The benefits of ketosis

In addition to providing a sustainable source of energy, ketones – and BHB in particular – may help reduce inflammation and oxidative stress, which are thought to play a role in the development of many chronic diseases. In fact, there are several established benefits and potential benefits of being in nutritional ketosis.

Established benefits:

  • Appetite regulation: One of the first things people often notice when they're in ketosis is that they're not as hungry as they often are. In fact, research has shown that ketosis suppresses your appetite. Studies also show a decrease in ghrelin, the so-called "hunger hormone". 
  • Weight loss: Many people automatically eat less when they limit carbohydrates and are allowed to eat as much fat and protein as they need to feel full. Because keto diets suppress appetite, decrease insulin levels, and increase fat burning, it's no surprise that they've been shown to outperform other diets intended for weight loss.
  • Reversal of diabetes and prediabetesIn people with type 2 diabetes or prediabetes, being in ketosis can help normalize blood sugar and insulin responses, potentially leading to stopping their diabetes medications.
  • Potential for improving athletic performance: Ketosis can provide an extremely long-lasting refueling during sustained exercise in both elite and recreational athletes.
  • Maintenance management: Maintaining ketosis with the classic keto diet or the less stringent modified Atkins diet (MAD) has been shown to be effective for epilepsy control in both children and adults unresponsive to antiepileptic drugs.

There is also excellent research, albeit in its early stages, suggesting that ketosis may be beneficial for many other conditions, such as reducing the frequency and severity of migraines, reversing PCOS, perhaps improving conventional cancer therapies to the brain, possibly slowing the progression of Alzheimer's disease, along with potentially helping people live longer, healthier lives. While higher quality research is needed to confirm these effects, much of the early research is very encouraging.

Nutritional ketosis vs ketoacidosis

Nutritional ketosis and diabetic ketoacidosis are completely different conditions. While nutritional ketosis is safe and beneficial to your health, ketoacidosis is a medical emergency. Unfortunately, many healthcare professionals don't quite understand the distinction between the two.

Ketoacidosis occurs mostly in people with type 1 diabetes if they are not taking insulin. In diabetic ketoacidosis (DKA), blood sugar and ketones rise to dangerous levels, which disrupt the blood's delicate acid-base balance. In nutritional ketosis, however, BHB levels typically remain below 5 mmol/L. However, people with diabetic ketoacidosis often have BHB levels of 10 mmol/L or higher, which is directly related to their inability to produce insulin.

Other people who can potentially go into ketoacidosis are those with type 2 diabetes who take medications known as SGLT2 inhibitors, such as Invokana, Farxiga, or Jardiance. Also, in rare cases, women who don't have diabetes can develop ketoacidosis while breastfeeding. However, for most people who are able to produce insulin, it is nearly impossible to enter ketoacidosis.

The tricks to get into ketosis

There are several ways to enter nutritional ketosis safely and effectively.

  • Reduce your net daily carbohydrate intake to less than 20 gramsWhile you may not need to be so strict, eating fewer than 20 grams of net carbs per day virtually guarantees you'll achieve nutritional ketosis.
  • Try intermittent fasting: Going 16-18 hours without eating can help you get into ketosis faster. This is easy to do by simply skipping breakfast or dinner, which can also feel very natural on a ketogenic diet, because it suppresses your appetite.
  • Don't be afraid of fat: Eating lots of fat is a necessary and delicious part of the ketogenic diet! Be sure to include a natural fat source with every meal.
  • Cook with coconut oil: In addition to being a natural fat that remains stable at high temperatures, coconut oil contains medium-chain fatty acids that can increase ketone production and may have other benefits as well.
  • Exercise if possible: During the transition to ketosis, you may not have enough energy to engage in vigorous physical activity. However, a simple brisk walk can help you get into ketosis more easily.
keto diet

Supplements are not required

Notice what's not in the above list: You don't need expensive supplements, like exogenous ketones or MCT (medium chain triglyceride) oil. These supplements probably won't help you lose weight or get reverse disease. Or at least, there is no evidence of this.

It's hard to believe that they have any direct benefits for weight loss or reversing type 2 diabetes. What these ketone supplements could do is perhaps improve mental and physical performance for a short period of time.

As far as we know, this potential is unproven. They raise blood ketone levels, an effect that can last anywhere from one to a few hours. We are not saying don't buy these supplements. Maybe you want to try them yourself, and see how they make you feel. But you don't need it to be successful on a ketological diet or to get into ketosis. 

The effects of protein on ketosis

While getting enough protein in any diet is important to prevent muscle loss, many questions have been raised about the impact of protein on ketone levels.

During digestion, the protein is broken down into individual amino acids, which trigger the release of insulin. Although the amount of insulin required to transport these amino acids to the muscles is small, when large amounts of protein are consumed, the increased insulin could potentially reduce ketone production to some extent. For this reason, ketogenic diets for epilepsy are limited in both protein and carbohydrates, which ensures that ketone levels always remain high.

However, the effect of protein on ketosis appears to be very subjective. So far, the scientific literature does not support the concern that too much protein worsens blood sugar control for most individuals. For example, three studies have shown that a diet with 30% calories from protein improves glycemic control. And another study found that patients with type 2 diabetes who ate a 50g protein meal had no significant increase in serum glucose concentration.

If you want to stay in ketosis and continue to eat lots of protein and are concerned about potential negative effects, it might be a good idea to conduct your own experiments to determine your personal protein threshold. It may be taller than you think. 

What is the optimal level of ketosis?

Entering ketosis with a ketogenic diet is neither immediate nor drastic: it is not as if we were in or out of ketosis. Instead, different degrees of ketosis can be achieved. The definition of “optimal” ketosis can vary depending on your goals. For example, treatment of seizures may require a higher ketone level, while weight loss or blood sugar improvement may be less dependent on the degree of elevation. 

  • Below 0.5 mmol/L it's not considered "ketosis," even though a value of, say, 0.2 shows it's getting close. At this level, you may not be at the peak of your fat burning zone.
  • Between 0.5 – 3 mmol/l it is nutritional ketosis. You will probably get a good effect on your weight and metabolic improvements.
  • Approximately 1.5 – 3 mmol/l it is called by some “optimal” ketosis. However, the concept of optimal ketosis is controversial, and it's unclear whether it offers substantial benefits over the 0.5-1.5 level. Exceptions would be the treatment of epileptic seizures or those interested in maximum gains in mental and physical performance.
  • Above 3 mmol/l is more than necessary. It will probably perform no better or worse than the 1.5-3 level. Sometimes, higher numbers can also mean that you don't get enough food ("starvation ketosis"). In people with type 1 diabetes, ketone levels above 3.0 mmol/L can be caused by a severe insulin deficiency requiring urgent medical attention.
  • Over 8-10 mmol/l: It's normally impossible to get to this level on a keto diet alone. It means something is wrong. By far the most common cause is type 1 diabetes, with severe insulin deficiency. Symptoms include nausea, vomiting, abdominal pain and confusion. The possible end result, ketoacidosis, can be fatal and requires immediate medical attention.

The signs to understand that you are in ketosis

There are several signs that suggest you are in ketosis, although measuring ketones is the only objective way to verify this. Here are the most common:

  • Dry mouth or metallic taste in the mouth.
  • Increased thirst and more frequent urination.
  • “Ketous breath” or “fruity breath,” which may be more noticeable to others than to yourself. To know more.
  • Initial tiredness, followed by a surge of energy.
  • Decreased appetite and food intake (one of the more pleasant side effects!).

The measurement of ketones 

ketone meters

There are three ways to measure ketones, all with pros and cons. For a detailed comparison, check out our comprehensive guide on the best way to test for ketones.

For a shorter version, read on below. Please note that we have no affiliation with any of the brands mentioned here.

  1. Urine strips: They are the simplest and cheapest way to measure ketosis. Not for nothing is it the first option for those who are new to the keto diet. Just insert the strips into your urine and wait 15 seconds. The color will change depending on the presence of ketones.
  2. Breath Ketone Analyzers: Breath ketone analyzers are another very simple way to measure ketones. However, they are more expensive than urine strips, although more convenient than blood testing machines.
  3. Blood ketone meters: They are the most effective tool for checking the level of ketones. Less cheap than the other tools, they are however very accurate.

What if you're not in ketosis?

If you're following a keto diet but aren't seeing any signs or symptoms of ketosis, here are some strategies that may help or some foods.

  • Track your carbohydrate intake. While we don't recommend counting or tracking calories, it can be helpful to log your carb intake to make sure you're really eating fewer than 20 grams of carbs. Use an online site or application, such as Chronometer, Senza, Carb manager and others.
  • Test blood ketones in the late morning or afternoon. Blood and urine ketones vary throughout the day, as well as from person to person. Many people find that their blood ketone levels are usually lowest soon after waking up. Try testing later, preferably a few hours after eating. Even if you're in ketosis for only part of the day, you still get some benefits, as discussed in this talk by Dr. Steve Phinney: Achieving and Maintaining Nutritional Ketosis.
  • Try to be patient. While some people transition into ketosis relatively quickly, it may take some time for others. Unfortunately, people who are insulin resistant often seem to have a longer journey. Put in a solid month of steady keto eating and try to increase your physical activity if possible. Within four weeks, you should definitely be in ketosis and experiencing its benefits. 

Side effects, fears, potential harm

Side effects typically show up in the first few days of starting a ketogenic diet and include headaches, fatigue, dizziness, irritability, cramps, and constipation. These are collectively known as the "keto flu," which can be remedied by, among other things, managing your fluids and electrolytes. 

Is being in ketosis safe for everyone?

Being in ketosis is safe for most people, and it can provide many health benefits, including weight loss, optimal blood sugar and insulin levels, to name just a few.

However, some individuals should only follow a ketogenic diet under medical supervision, while others are better off avoiding it altogether.

Conditions that require medical supervision and monitoring during ketosis:

  • Type 1 diabetes
  • Type 2 diabetes on insulin or oral diabetes medications
  • High blood pressure on medication
  • Diseases of the liver, heart or kidneys
  • History of gastric bypass surgery
  • Pregnancy

Conditions for which ketosis should be avoided:

  • Breastfeeding women
  • Individuals with rare metabolic conditions typically diagnosed in childhood, such as enzyme deficiencies that interfere with the body's ability to make and use ketones or digest fats properly.