The ketogenic diet is a high-fat, low-carbohydrate, and moderate-protein diet that has been proved to be an effective treatment among patients with epileptic conditions, such as glucose transporter 1 deficiency, pyruvate dehydrogenase deficiency, tuberous sclerosis complex, Rett syndrome, Dravet syndrome, and specific mitochondrial disorders (1, 2).
Keto diet is also associated with reduced body weight and insulin resistance, thus it can be beneficial with obesity and diabetes type 2 patients (3).
There are also many major benefits of ketogenic diet such as improving cardiovascular health, brain function, and having therapeutic effects in several other chronic conditions.
What you should be aware of is the difference between ketosis and ketoacidosis because they are two very different things. Ketosis is a natural metabolic state whereas ketoacidosis, also known as diabetic ketoacidosis (DKA), is a dangerous condition in people with diabetes.
Nonetheless, keto diets are also related with some adverse effects, most of them are temporary side effects and easily treated.
Here we have a list of negative side effects of ketogenic diet, mostly occur at the beginning and some of them will go away on their own once you are fat-adapted.
Remember these are only temporary and small side effects and not everyone will get these. In fact, a lot of people thrive on keto without experiencing these effects at all.
7 Most Common Side Effects
#1. Keto Flu
One of the most frequent adverse effects of the keto diet is the “low-carb flu” or “keto flu”, sometimes known as the induction flu. Symptoms usually include headache, weakness, brain fog, increased hunger, and fatigue.
This happens usually because your body runs on glucose for energy, which derives from carbohydrates. By reducing the carbohydrate intake in a ketogenic diet, your body starts burning fat, a metabolic state known as ketosis (4).
However, your body needs a few days to adjust to this new metabolic state and during this period, your body expresses flu-like symptoms.
These flu-like symptoms can last between 2-3 days up to 2-3 weeks for some people, just enough time for your body to adapt in the ketosis state.
Not everyone will experience the flu, it depends on your body and how carb-dependent you were before starting this diet.
Meanwhile, useful suggestions for this adverse effect include hydration and patience.
A trick that could help is a glass of water and half a teaspoon salt, which can minimise the symptoms in less than 30 minutes. Taking electrolyte supplements or drinking bone broth can also help.
Moreover, adding more healthy fats to your diet could help reduce the fatigue and increase feeling of satiation (fullness).
#2. Keto Bad Breath
During the fat metabolism, your acetone levels rise and your body disposes of them via your breath or your urine (6).
So if your breath smells fruity, it is good news as you are in the stage of ketosis and you will start losing weight!
This adverse effect is also temporary and usually, after 1 or 2 weeks, the bad smell goes away.
Nevertheless, there are some strategies to help with the keto breath.
- Stay hydrated and increase the amount of water you drink
- Keep an excellent oral hygiene. Do not forget to brush twice a day and also floss often.
- Use a breath freshener or sugar-free gums. Mint or spearmint chewing gums or mouth sprays can mask the bad breath
- If the keto breath continues for more than two weeks, try to reduce the degree of ketosis by slightly increasing the amount of carbs. You can try eating 50 grams of carbohydrates per day (which will likely kick you out of ketosis) but at the same time combine it with some occasional fasting, so you can still gain the benefits of low carb diet without the acetone-like smell.
#3. Digestive Problems
Common issues with the keto diet involve digestive problems, such as constipation and diarrhea, even among children (7).
Lack of fiber in the ketogenic diet is likely to cause constipation, especially in the beginning of the diet scheme (8).
Although constipation is a common complication of the ketogenic diet, it is easily treatable. Some simple tricks to avoid or treat constipation include:
- Increased water and salt intake
- Eat more non-starchy and fiber-rich green vegetables.
- If constipation continues, consider magnesium citrate supplement or probiotics (9).
Some people also experience diarrhea, and that is usually the case when they reduce fat consumption together with carbohydrate restriction. Your body needs time adjusting to this new ratio of nutrients, so just be patient and do not reduce the fat intake.
#4. Leg Muscle Cramps
While on the keto diet, it is not uncommon for people to experience muscle cramps, especially in their legs.
This happens mainly due to dehydration and loss of minerals. As ketogenic diet is traditionally initiated with a period of fasting and fluid restriction, dehydration is a logical adverse effect (10).
There are some simple ways to avoid leg cramps:
Avoid fluid constraints before starting the keto diet because fluid restriction is not essential for the keto diet and you will avoid any mineral loss and muscle cramps (11).
Make sure to drink plenty of water. In case the cramps continue, you can also try magnesium supplements (12).
#5. Decreased Physical Performance
A relatively common but short-term effect of the keto diets is the decreased physical performance.
As carbohydrate is usually the main source of energy and the sudden restriction of the carbohydrate results in impaired physical activity in the beginning of the keto diet (13).
However, after the body adapts to the ketosis, it returns to its previous physical state and performance.
Therefore, an initial weakness or reduction in athletic performance can be noted in the beginning of a ketogenic diet, but adaptation time is all it is needed.
Further, sodium and potassium supplements could help with this adverse effect.
#6. Low Blood Sugar (Hypoglycemia)
Another common side effect is low blood sugar or hypoglycemia.
Hypoglycemia is related to different types of symptoms, such as headaches, blurred vision, dizziness, irregular heart rhythm, irritation and could even result in seizures or unconsciousness (16).
In the ketogenic diet, the human body is forced to use fat instead of glucose as an energy source, which can cause hypoglycaemia (17).
Carbohydrates are the main source of glucose, hence the restriction of carbohydrates may result in lower glucose levels (18).
Hypoglycemia, meaning low blood glucose levels, is relatively uncommon among people without diabetes, thus one of the main reasons hypoglycaemia is related to the keto diet is because diabetic people often receive ketogenic diet to treat type 2 diabetes (19).
Hypoglycemia is just a short-term experience. Some simple solutions against low blood sugar are drinking plenty of water, increasing meals frequency and oral magnesium supplements (20).
#7. Increased Heart Rate (Heart palpitations)
Another side-effect that people who begin with keto diet report are heart palpitations.
Heart palpitations occur when you feel your heart beating too fast or too hard (21).
This is not a symptom to worry about as it occurs frequently in the first days of the keto diet. When you begin the keto diet, you experience an initial water loss and a reduction in salt intake. Lowering salt consumption could result in increased heart rate (22).
Making sure that you stay hydrated and adding more salt in your diet either directly in your meals or drinks.
Other Less Common and Very Rare Issues on Low Carb Diet
Reduced Bone Mineral Content (BMC)
However, these studies face many limitations and in most cases, the reduced bone mineral content was caused by vitamins deficiency.
Kidney Stones Formation (Nephrolithiasis)
Formation of kidney stones is also a less common side effect associated with the keto diet. Nonetheless, the majority of people who developed kidney stones had increased risks of nephrolithiasis (25, 26).
To minimize the risk, consider adding oral potassium citrate supplement, lemon water, apple cider vinegar and cranberry juice (in moderation) in your diet as prevention against kidney stones (27, 28, 29, 30, 31, 32, 33).
Temporary Hair Loss (?)
Some people say they experience some hair loss the first weeks of the keto. This is NOT a very common adverse effect and is always temporary. In fact, many people experience a better and healthier hair and nails growth on keto.
If you still experience hair loss, it’s due to many factors and probably not from keto diet. It could mean you are not eating enough calories, protein, vitamins and nutrition your body needs to growth hair, nail and skin such as collagen.
You can get collagen from your diet or supplements. The best form to take is collagen protein powder. You can easily add it to your coffee, smoothie, drinks, etc… Many people notice a huge difference in their hair and nails growth after taking collagen for a few weeks.
Although quite uncommon, keto rash or itching has been accounted as a side-effect of the keto diet. As your body enters the ketosis phase, it produces the ketone acetone which can be irritating in high concentrations. Comfortable clothing, frequent showers and avoiding exercises or places which you will sweat can help.
In contrast to this, keto diet has shown many therapeutic uses including improved skin quality and reduced acne (34).
Raised cholesterol levels
However, a few people might experience a temporary rise in cholesterol levels on low carb diet during the first 6 months. After that, the LDL-cholesterol will decrease (38).
As there is no clear mechanism or scientifically proven effect, omega-3 fatty acid supplements can be used as a preventive method against raised cholesterol levels (39).
Reduced tolerance to alcohol
As your liver is burning fat and producing ketones, it has less capacity to burn alcohol, hence your tolerance to alcohol is decreased. Therefore, you should be careful of your drinks consumption.
This side-effect is very rare and it can easily be prevented by adding selenium supplements to your diet (42).
Although acute pancreatitis is a serious condition, its incidence with the ketogenic diet is extremely low and there is no scientific association between ketogenic diet and pancreatitis (45).
It would be advisable for people with high triglycerides levels and other lipid metabolism issues to consult with their doctors prior to receiving a ketogenic diet.
Gastrointestinal (GI) intolerance
In the ketogenic diet, the human body is forced to replace sugar-which is usually the energy source- with fat, thus it could cause fat intolerance or a general gastrointestinal intolerance. Symptoms include nausea, vomiting, abdominal pain, and diet refusal (46).
Nonetheless, the majority of the GI symptoms were related to antiepileptic drugs and steroid medication of the patients prior the initiation of the ketogenic diet and to a medium-chain triglyceride ketogenic diet (47).
How To Avoiding Ketosis Side Effects
Although there are some side-effects which on the surface are not related, they all occur due to your body adjusting in the ketosis stage from its usual glycolysis metabolic pathway. Thus, there are some simple methods to avoid or treat the keto diet adverse effects.
Provide time to your body to adjust. Most side effects, including keto flu, bad breath, diarrhea happen because your body needs time to adapt to the ketosis.
Drink plenty of water. Dehydration is quite common among people who begin with the ketogenic diet and is also related to other side-effects. Ensure that your daily water consumption is at least 2 liters a day.
Increase your salt intake. Loss of sodium occurs when you restrict the carbs consumption and it can also cause heart palpitations, fatigue, leg cramps and reduced physical performance. Try adding salt to a glass of water and your meals, especially in the first few days of the diet.
Add fiber to your diet. Digestive problems and especially constipation usually occurs to the lack of fiber in your diet. Consider eating non-starchy vegetables.nuts and seeds.
Try supplements. In case one or more side-effects persist, try magnesium supplements for low blood sugar and cramps or sodium and potassium supplements for better physical performance.
Keto diet is a proven treatment for drug-resistant epilepsy and also a powerful means to fight obesity and diabetes. Many people have transformed their lives as result of following this diet. You can read their success stories here.
Nonetheless, as every diet, it is also correlated with some side effects, with the most common ones being keto flu, bad breath, stomach issues, hypoglycemia, and dehydration, all of which can be easily be prevented or treated with dietary supplements or medication.
Some more serious complications involve bone mineral content loss, nephrolithiasis, and acute pancreatitis, which however are extremely rare and are often associated with previous medical conditions or medications of the people following the ketogenic diet.
The benefits of a ketogenic diet far outweigh any minor and temporary side effects, therefore, you should not worry too much about this. Give keto an honest try to experience the full benefits of ketosis. If you have pre-existing medical conditions or rare diseases, make sure to talk to your doctor before trying any new diet.