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Health & Nutrition
Dimitar Marinov
Senior Product Researcher MD, PhD, Assistant Professor

Is Ketosis Bad For You?

The ketogenic diet aims to achieve ketosis, a state where the body primarily uses fats for energy. It is believed to offer benefits like weight loss and improved mental performance. However, some caution against ketoacidosis, a dangerous condition. This article explores the pros and cons of the keto diet and provides tips to navigate potential setbacks. With proper guidance, the keto diet can be a viable option for those seeking its advantages.

Ketosis is the ultimate goal of the ketogenic diet practitioner. People who follow the diet often swear that It’s the most effective state of your body for weight loss, mental performance, and metabolic health.

Yet, others argue that ketosis can be unsafe for some, and it’s just a step away from a dangerous condition called ketoacidosis.

To decide whether the keto diet is for you, you should look at the scientific evidence on the topic and weigh all the pros and cons of this popular dietary regime.

This article aims to explain the benefits and risks of the keto diet and the best ways to avoid the most common setbacks during your keto diet journey.


Ketosis Explained

Even though most of your organs and tissues can burn fatty acids, glucose is the primary energy source for your body during sufficient carbohydrate intake. Some organs, such as the brain, cannot use fatty acids.

Yet, your body has a mechanism called ketogenesis that allows it to survive fasting or complete carbohydrate deprivation for prolonged periods. 

Ketogenesis is when your body breaks down fats and ketogenic amino acids to produce ketone bodies. Ketone bodies are acetone, β-hydroxybutyrate, and acetoacetate. 


If ketogenesis is highly active and you have elevated ketone levels in your body, you are in a state called ketosis. In this state, your body has switched from mainly blood glucose to mostly ketones to fuel critical organs. 

The organs that can use ketone bodies and glucose are the brain, the heart, and the skeletal muscles.

Acetoacetate and β-hydroxybutyrate are the ketone bodies that can easily pass through membranes and thus become the brain’s primary energy source during ketosis.

For example, studies suggest that after three days of fasting (or carbohydrate deprivation), ketone bodies account for approximately one-fourth of the brain's energy requirements (1).


Ketone bodies can account for more than half of the brain’s energy requirements in prolonged fasting or carbohydrate deprivation.

The trigger for boosting ketogenesis and entering ketosis is the depletion of glycogen. Glycogen is the form of glucose energy reserve that is stored mainly in your liver and skeletal muscles.


During ketosis, your body still produces some amounts of glucose from other sources, such as lactate, glucogenic amino acids, and glycerol. 

This process, called gluconeogenesis, ensures a stable glucose level since your brain still needs some amount of glucose to function properly (2). 


Ketosis vs ketoacidosis

Gluconeogenesis maintains stable insulin secretion and thus prevents excessive production of ketones which can lead to a life-threatening condition called ketoacidosis.

Ketoacidosis occurs when insulin secretion is severely suppressed, or there is a complete lack of insulin due to problems with the pancreas. 


A total lack of insulin occurs in type 1 diabetes (insulin-dependent) and advanced cases of type 2 diabetes. Therefore the condition is called diabetic ketoacidosis, one of the most severe acute complications.

Diabetic ketoacidosis is the leading cause of death amongst young patients with type 1 diabetes.

Ketoacidosis may also occur due to excessive alcohol consumption, starvation during an illness, medications, and toxins. 

The excess of ketones in ketoacidosis leads to changes in the pH of the blood and metabolic acidosis. 

Symptoms of diabetic ketoacidosis include nausea, vomiting, abdominal pain, weakness, confusion, rapid, deep breathing, and eventually, loss of consciousness.


Unlike ketoacidosis, ketosis is a physiological state in which your body can control its ketone production and maintain a stable pH. 

Both ketosis and ketoacidosis can lead to your breath smelling like acetone. To assess whether you are in ketosis or ketoacidosis, you can measure ketone levels in blood, urine, or breath. 


For example, the levels of β-hydroxybutyrate in your body should be between 0.5 and 3.0 millimoles (mM) during physiologic ketosis (3). 

Levels of β-hydroxybutyrate above 3mM are an indicator of ketoacidosis. In severe cases of the condition, β-hydroxybutyrate concentrations may even exceed 10mM.


The Keto Diet Hype

What are the benefits of the ketogenic diet?

The ketogenic diet is a way to induce ketosis without having to fast or starve. Since ketosis is a state in which your body uses primarily fats for energy, the diet is claimed to have numerous health benefits.


Arguably, the most popular benefit of the keto diet is rapid weight loss. Studies confirm that the diet can deliver results quickly since cutting all your carbs can result in a substantial caloric deficit and flush large amounts of water out of your body (4).

Remember that even in ketosis, calories matter, and you will not lose weight unless you are in a deficit. Studies suggest that the fat loss during keto diets is comparable to other calorie-matched diets (5). 

Ketones also suppress the appetite centers in the brain, which can help reduce your cravings and stick to your diet in the long term (6).


Since you won’t consume any carbohydrates on a keto diet, you will not experience significant variations in your blood sugar levels. 

Thanks to the rapid weight loss and the stable blood glucose levels they provide, ketogenic diets can help improve blood sugar control in patients with diabetes (7). 

That is because of the beneficial effects of fat loss on insulin resistance, which is the hallmark of Diabetes Mellitus. A significant reduction of abdominal fat may even lead to an improvement in type 2 diabetes.

Furthermore, losing extra body fat has also been reported to lower your risk of chronic and debilitating conditions such as heart disease and cancer (8, 9).


One of the unique benefits of the keto diet and ketosis is reducing symptoms of epilepsy (10). It’s been shown to help reduce the incidence of seizures in patients who fail to respond to the standard medical therapy for epilepsy.


What are the different types of ketogenic diets?

There are different types of ketogenic diets. Some less restrictive approaches are cyclical, targeted, and high-protein keto diets. Yet, these involve increased consumption of carbohydrates or protein, and they do not lead to full ketosis (11).

People looking forward to building muscle and achieving peak performance may need higher carbohydrate intake to replenish their glycogen stores more effectively. That is especially true if they train daily.

Yet, the standard ketogenic diet is the only one that will successfully put you into ketosis if you follow it strictly for a prolonged period. It is best for people with relatively low physical activity and therefore does not need as much of the rapid energy source as glucose.


To enter a state of ketosis successfully, the standard keto diet requires a severe restriction of your carbohydrate intake down to 20-50g a day or less than 5% of total daily energy intake (12). The keto diet is also called a very low-carb diet (VLCD).

Dietary fiber is the only type of carbohydrate that is not restricted. That’s because it does not get digested but acts as a ballast and improves digestion (13). Fiber gets fermented by your gut bacteria into short-chain fatty acids.

Furthermore, proteins should be limited to 15-20% of your total energy intake since they contain glucogenic amino acids that boost gluconeogenesis and raise insulin (14).

Thus, most of your calories during a keto diet should come from healthy fat, comprising at least 75-80% of your total daily calories.


Keep in mind that it takes some time until your body depletes its glycogen stores. Thus consistency is key to being successful in your keto diet journey.


What are the side effects of the ketogenic diet?

Unfortunately, the keto diet is not free of adverse reactions. The first side effect you might experience when starting a keto diet is the keto-flu. It is caused by the depletion of glycogen and the low insulin levels in your body.

The glycogen depletion leads to water loss since every glycogen molecule normally binds and retains 3 water molecules (15). The rapid water flush leads to the loss of electrolytes like sodium. Low insulin levels also cause elevated sodium losses via increased kidney excretion  (16, 17). 


Sodium is in constant balance with many other electrolytes in the human body. Therefore, sodium depletion leads to the loss of other minerals such as calcium, potassium, and magnesium. 

The dehydration and electrolyte imbalance usually lasts about a week until your body fully adapts to ketosis. You may get a wide range of symptoms during this period, including nausea, abdominal cramping, muscle cramps, headache, insomnia, brain fog, constipation, cravings, and rapid heartbeat.

Once you are successfully in ketosis, the only unpleasant side effect you may experience includes the typical acetone breath. It is caused by the increased levels of acetone in your blood. You can use sugar-free gum or mouthwash to minimize this problem without any risk of breaking ketosis. 


People with certain chronic conditions or specific physiological states may experience serious adverse effects from the ketogenic diet.  This type of nutrition can worsen diseases such as acute and chronic kidney, liver, gallbladder, and pancreatic conditions.

The keto diet is also contraindicated in people who take certain diuretics. These patients may be at an increased risk of hypokalemia, which describes dangerously low potassium levels.

In addition, restrictive dietary regimes such as the ketogenic diet are not suitable for several population groups, including children, adolescents, pregnant women, breastfeeding women, and underweight individuals.


Tips to reduce the possible side effects of entering ketosis

The side effects of entering ketosis are collectively known as the keto flu. Keto flu is the number one reason people quit the keto diet - sometimes as soon as the first week.

Yet, the condition is transitory, and the symptoms will eventually disappear. Moreover, there are ways to minimize or even avoid most of the symptoms.

Here are the most effective tips to help you manage the keto flu:


Stay hydrated

Make sure you drink plenty of water during your first week of keto. Staying hydrated is vital since your body will lose a lot of water. In rare cases, the keto flu can lead to diarrhea, so replenishing your fluids is critical.

The research suggests drinking more water can help reduce some of the most common symptoms, such as headaches and water cramps (18). It may also help improve the consistency of your stools in case of constipation.

The general recommendation for the amount of water you should drink is at least 2.7 liters for women and 3.7 liters for men (19). 

These numbers are even higher if you live in an area with a hot climate, experience fever, or participate in intensive exercise.


Increase your intake of electrolytes

Do not forget to eat your low-carb veggies while on keto! These foods are incredibly rich in micronutrients that help replenish your electrolyte losses. 

For example, cruciferous vegetables, leafy greens, mushrooms, and artichokes are great potassium, magnesium, and calcium sources.

Yet, one fruit is on top of all vegetables in potassium content - the avocado. It has a whopping 1000 mg per medium-sized fruit (200g) (20).


Some of the best foods to include in your keto diet that are high in both potassium and magnesium are:

  • avocadoes
  • swiss chard
  • spinach
  • white button mushrooms
  • brussel sprouts
  • broccoli
  • artichoke

In addition to fruits and vegetables, make sure to incorporate some fatty fish into your keto diet lifestyle. For example, salmon and mackerel are low in mercury, and at the same time, they are excellent sources of potassium and magnesium. 

Also, they both have plenty of omega-3 and vitamin D - nutrients in which many people are deficient.


Avoid intensive exercise

Heavy lifting or strenuous exercise may worsen keto flu symptoms, such as fatigue, rapid heartbeat, and muscle cramps. Therefore it is best to abstain from such activities, at least for the first week of your keto diet journey.

Yet, light exercise such as brisk walking or jogging may help you enter ketosis faster and improve how you feel. It may help improve your sleep and fight insomnia, another keto flu symptom.



Ketosis is not bad for you if you are healthy and do not have any underlying conditions, as it is a physiological state which helps your body survive without carbohydrates. 

You may even reap some benefits while being in ketosis, such as suppressed hunger, better concentration, and also losing excess weight.

Unfortunately, you may have to go through the dreaded keto flu during your transition to ketosis, but remember that this is a temporary state which will go away within a few days.

Just stay hydrated, eat plenty of nutritious foods and avoid excessive sweating!


Note: This article is for informational purposes only, and not intended for use as medical advice. Always consult your healthcare provider before starting any dietary supplement.

Dimitar Marinov
Senior Product Researcher MD, PhD, Assistant Professor
Dr. Marinov is a licenced physician and scientist with years of experience in clinical and preventive medicine, medical research, nutrition and dietetics. His research is focused primarily on nutrition and physical activity as preventive measures to improve and preserve human health. He is passionate about creating evidence-based content about various medical topics and takes great care in referencing every statement with high-quality evidence.
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