Keto Diet: Side Effects That You Should Know

Parul Dube

July 29, 2022

The Keto diet has gained popularity because people are concerned about trying to be health-conscious and maintain the perfect weight. However, the basic premise of the keto diet plan focuses on the general population. Therefore, making modifications and personalising them according to individual needs is necessary. 

The ketogenic diet restricts carbohydrate intake, forcing the body to burn fat. Research shows that a long-term ketogenic diet’s beneficial effects include reduced body weight and body mass index. Furthermore, it decreased the level of blood glucose, triglycerides, and LDL cholesterol and increased the level of HDL cholesterol.

This low-carb, high-fat diet promises rapid weight loss, but health professionals are concerned about the risks and problems. From moodiness to brain fog, there are some strange keto side effects. There is a healthy way to follow keto, but there are also some side effects to be aware of before you begin.

An Introduction of Keto Diet

The keto diet aims to get energy and calories from fat rather than carbs. Therefore, low-carb, high-fat, and moderate protein intake are the three pillars of the keto diet.

Generally, the ketogenic diet suggests an average of 70-80% fat, 5-10% carbohydrate, and 10-20% protein. For a 2000-calorie diet, you can eat 165 grams fat, 40 grams carbohydrate, and 75 grams protein. 

According to research, low-carb diets cause the body to enter ketosis, where body fat and fat from food produce energy. During this process, it makes ketone bodies.

Still, the time it takes to enter ketosis, and the number of ketone bodies built in the blood depends on various parameters, including body fat percentage and resting metabolic rate.

Keto-friendly food items include:

  • Spinach
  • Bell peppers
  • Eggs
  • Almonds
  • Seeds
  • Healthy oils 
  • Avocados
  • Dark chocolate  
  • Chicken thighs
  • Fatty fish  
  • Greek yoghurt

The HealthifyMe Note

Knowing what not to eat on a keto diet is also necessary. Most times, people are unaware of the liquids that are not allowed on a keto diet. Also, besides sugary beverages, alcohols like wine, beer, and sweetened cocktails are not keto-friendly. 

Benefits of the Keto Diet

Weight Management

One of the key benefits of the ketogenic diet is the ability to lose weight quickly. When you restrict carbohydrates to the point where you’re in ketosis, you’ll notice a significant loss in body fat and an increase or retention of muscle mass. In addition, low-carb and ketogenic diets have been shown in studies to result in substantial weight loss over time.

Insulin Sensitivity

A ketogenic diet helps restore insulin sensitivity by addressing the root cause of insulin resistance, which is too much insulin in the body. Since low carbohydrate means low insulin, this diet helps keep insulin levels in check.

A high-carbohydrate diet worsens insulin resistance. High carbohydrate consumption means more insulin is needed, exacerbating insulin resistance. On the other hand, a ketogenic diet lowers insulin levels since fat is the macronutrient that requires the least insulin.

Helps Combat Brain Disorders

Because some regions of your brain can only burn sugar, it requires glucose. If you don’t eat carbohydrates, your liver creates glucose from protein. A significant part of your brain can burn ketones produced during fasting or low glucose intake. This diet can help youngsters with epilepsy in many circumstances.

In one trial, almost half of the children on a ketogenic diet saw a 50 per cent reduction in the number of seizures they had, and 16 per cent went seizure-free. Other brain disorders, such as Alzheimer’s and Parkinson’s, are currently being researched using very low-carb and ketogenic diets.

Can Improve Mental Health

Mental clarity, increased capacity to focus, and improved memory are other benefits of a ketogenic diet. In addition, increasing your consumption of omega-3 fats, such as those found in oily fish like salmon, tuna, and mackerel, will help you feel better and learn better.

Concerning Side Effects of the Keto Diet

Some health specialists strongly advise against keto, citing unpleasant side effects, health hazards, and the diet’s inability to be sustained. Before starting the ketogenic diet to lose weight, you should know a few things. You may lose weight, but keep an eye out for the following side effects or consequences.

The Keto Flu

The idea behind keto is to get your body into a state of ketosis, which burns fat instead of glucose. Keto flu is your body’s natural reaction to switching to ketones as an energy source, and symptoms include brain fog, headaches, nausea, and exhaustion. In addition, vomiting, stomach distress, extreme exhaustion, and lethargy are possible side effects. After a few days, the so-called keto flu usually passes.

Studies say these symptoms might not be exclusive to the ketogenic diet. For example, some patients report experiencing similar symptoms after cutting back on processed foods or opting for an anti-inflammatory diet. 

What to Do for Keto Flu?

It is not the flu, despite its name. You will not get a fever, and the symptoms seldom render you unconscious. However, if you’re feeling sluggish, see your doctor. 

Here are some tips to reduce the impact of keto flu. 

  • The best approach to managing keto flu is to start slowly and avoid drastic diet changes. 
  • Make sure you’re getting enough water. Some diets can cause dehydration.
  • Eat more frequently and include a variety of coloured veggies in your diet.
  • Don’t give up. You may feel weary for a few days, but your energy level will most likely return to normal by the end of the week, and you might even feel better.


Diarrhoea occurs from a lack of fibre in the keto diet, which can happen when someone cuts out carbs (like whole-grain bread and pasta) and doesn’t supplement with fibre-rich foods like vegetables. 

The keto diet is 70 to 80% fat. However, some people don’t digest fat, and their systems don’t utilise fat as well as they should. So the stools become more fluid than usual due to the additional fat your body isn’t using. Another cause of keto diarrhoea is replacing sugar with non-nutritive sweeteners (like stevia) or sugar alcohols (like sorbitol or xylitol).

How to Stop Keto-Induced Diarrhoea?

If you’re serious about trying keto and are experiencing diarrhoea, stay hydrated and add fibre. Adding more vegetables to your diet, such as leafy greens and broccoli, can help you get more fibre. If that’s not your thing, consider taking a fibre supplement.


Ketoacidosis is a critically poisonous quantity of acid in the blood caused by too many ketone bodies. In addition, the kidneys begin to expel ketone bodies with body water in the urine during ketoacidosis, resulting in fluid-related weight loss.

Ketoacidosis is most common in persons with type 1 diabetes, who lack the hormone insulin, which prevents excess ketones from being produced, confirms the data

Studies say that ketoacidosis symptoms include dry mouth, frequent urination, nausea, poor breath, and breathing difficulties. 

How to Manage Ketoacidosis?

  • Check your urine for ketones if your blood glucose level exceeds 240 mg/dl.
  • Avoid the keto diet if ketones are found in the urine and have high blood glucose levels. 
  • Follow the doctor’s treatment plan with insulin consuming a nutritious and well-balanced diet. 

Possible Kidney Damage

According to studies, kidney stones are a common consequence for children who follow the diet, with about 5% of patients experiencing the problem. It is, however, curable. Kidney stone production is linked to hypocitraturia and hypercalciuria when acidosis promotes bone demineralisation.

Low pH in the urine can also increase the production of crystals, leading to kidney stones. Because the body loses electrolytes such as sodium, magnesium, and potassium due to increased urination, Acute renal damage can result from this. In addition, dehydration is dangerous because it can cause dizziness, renal impairment, and kidney stones.

How to Cure/Prevent Kidney Stones Due to the Keto Diet?

Although water is best, other liquids, such as citrus drinks, can also help prevent kidney stones.

  • Limit your salt consumption.
  • Keep yourself hydrated.
  • Eat animal protein in moderation.
  • Avoid foods that cause stones, those high in oxalates
  • Avoid excess vitamin C supplementation 

Possible Weight Gain 

Dieters advertise the keto strategy as a quick way to drop a dress size or two, but they’re typically disappointed when the weight creeps back on after a “cheat” day. According to curated data, the body stores every gram of carbohydrate with around 4 g of water.

As a result, low-carb dieters appear to lose water weight. Because the keto diet is limiting, health experts warn it is not a long-term healthy eating plan. Weight fluctuations like these can lead to disordered eating.


The lack of carb-rich whole grains, legumes, fruits, and starchy vegetables like sweet potatoes leads to constipation. So unless you’re increasing your greens intake religiously, there’s a strong chance you’re not receiving the recommended 25-38 grams of fibre per day. In addition, constipation can make your faeces firm and lumpy, making them difficult to pass. 

How to Prevent and Cure Constipation?

  • Increase your water intake.
  • Temporarily increase your intake of fibre-rich foods, including whole grains, beans, and berries.
  • After each meal, go for a vigorous walk.
  • Try bowel training, a technique that involves passing faeces at the same time every day.

Hair Loss 

Although common, hair loss isn’t unavoidable on the keto diet. Most keto dieters generally restrict carbs and calories and lose weight, both of which cause hair thinning and loss.

Other causes of hair loss include vitamin and mineral shortages (particularly zinc and biotin) and adverse microbiome alterations caused by a restrictive and high-fat diet.

How to Prevent Hair Loss Due to Keto?

  • Take a multivitamin to offset any potential deficiencies and help prevent hair loss.
  • Get your protein and biotin from foods like almonds, onions, tomatoes, walnuts, salmon, pumpkin seeds, cashews, and high-quality sources like eggs and chicken.
  • Consult with someone who can assist you in tailoring an eating plan to your specific needs.

Bad Breath

One of the most common complaints keto dieters (and their partners) have is their embarrassingly awful breath. Some even claim that their mouths have a metallic taste. Acetone is a stinky volatile molecule that is one of the ketone bodies (compounds generated by fatty acid metabolism).

Because ketones, like Acetone, are expelled from the body through exhalation, sweating, and urination, smelling like a nail salon is a good indicator that you’re in ketosis. The good news is that this adverse effect will usually fade away as your body adjusts to running on ketones. 

Home Remedies for Keto Breath

  • Increase your water consumption.
  • Reduce your protein intake.
  • Maintain proper dental hygiene.
  • Use mints and gum to mask odours.
  • Increase your carbohydrate intake.
  • Wait patiently.

Risk of Bone Fracture

A small recent animal study shows that the ketogenic diet may harm your bones. Researchers observed professional athletes on the keto diet undergoing intensive training and found more evidence of bone disintegration and fewer signs of healing than athletes on a higher-carb diet.

Menopausal women following the keto diet are at a greater risk of bone fractures. It is due to changes in insulin-like growth factor 1 levels and the effects of acidosis. Acidosis causes bone degradation, weakening the bones and making them susceptible to fractures. 

Supplementing a diet with more vitamins and minerals helps individuals on the ketogenic diet manage bone-related side effects. You can also take multivitamin, calcium, and vitamin D supplements. 

Less Muscle Mass and Decreased Metabolism

The reduction of muscle mass is another side effect of keto-related weight loss. You’ll lose weight, but it may be mostly muscle, influencing your metabolism because muscle burns more calories than fat. It’s not always in the same proportions when someone quits the ketogenic diet and regains a significant weight.

Some people may have leg cramps during ketosis. These can be uncomfortable and indicate you need to drink more water. Dehydration and mineral loss are ketosis’s most common causes of leg cramping. It is because ketosis promotes a loss of water weight. 

If you have any of the following conditions, you should avoid the keto diet:

  • Liver failure pancreatitis
  • Deficit in carnitine
  • Diseases of porphyria that impair the way their bodies digest fat

Increased Heart Rate 

As a side effect of ketosis, some patients report an increased heart rate. This condition is also known as palpitations or a racing heart. 

Your heart health depends on what you eat. The keto diet based on plant sources of fat and protein can lower heart disease risk by 30%. However, it is the opposite for people mostly eating animal-based proteins and fats.

Other Adverse Effects

Bad breath, weariness, constipation, irregular menstrual periods, decreased bone density, and sleep problems are possible adverse effects. Other impacts lack solid evidence, primarily because it is challenging to track dieters over time to determine the long-term effects of a diet plan. For example, doctors don’t know how it affects blood cholesterol levels; some suggest a rise, while others show a drop. 


Following a high-fat, low-carb regimen is not simple or enjoyable, but at the very least, you need to be more prepared for what lies ahead. You might experience unpleasant sensations in the first few days after changing your diet. However, this should not be the deciding factor when picking what to eat. In an ideal world, you should eat a nutritionally dense diet, and the Mediterranean and DASH diets have the most evidence to support living a long and healthy life. A medical expert can also assist you in safely following the diet to reduce the chance of side effects.

Frequently Asked Questions ( FAQs) 

Q. Who should not do keto?

A. Anyone with kidney disease, is at risk for heart disease, is pregnant or nursing, has type 1 diabetes, has a pre-existing liver or pancreatic issue, or has had their gallbladder removed should avoid the keto diet. In addition, keto can be a restrictive diet for most people. However, some are metabolically flexible and adapt well to keto. 

Q. Is the keto diet healthy in the long term?

A. The keto diet might increase the risk of vitamin or mineral deficiencies in the long run if a person does not consume adequate nutrients. In addition, they may be more prone to heart disease if they ingest a lot of saturated fat. People with chronic conditions like kidney disease should not follow the keto diet.

Q. How long do keto diet side effects last?

A. Keto adaptation may cause some ‘brain fog,’ but this will pass after the body has fully adapted, and some people will feel sharper at this time. Keto adaptation is estimated to take four weeks on average. However, the adverse effects usually fade away quickly.

Q. Why is the keto diet unhealthy?

A. The keto diet has been related to low blood pressure, kidney stones, constipation, dietary deficiencies, and heart disease risk. In addition, strict diets, such as keto, can cause social isolation and eating disorders. Anyone with issues with their pancreas, liver, thyroid, or gallbladder should avoid keto.

Q. Can I drink alcohol on keto?

A. For example, pure alcohol, such as whiskey, gin, tequila, rum, and vodka, are carb-free. You can drink these drinks with low-carb mixers for added flavour. However, most wine and beer are not keto-friendly. 

Q. How long should you stay on a keto diet?

A. While some people have succeeded in keeping on the keto diet for a long time, “long-term study is sparse.” Therefore, before reintroducing other low-carb foods to your diet, healthcare specialists recommend going on keto for only six months.

A. Physical activities like jogging, biking, rowing, and yoga are just a few that may be very useful on keto. However, while you can incorporate any additional activities into your fitness program that you prefer, some high-intensity exercises may be more challenging on the ketogenic diet.

Q. Why do I feel weird on the keto diet?

A. People transitioning to a ketogenic diet often experience fatigue and irritation. The stress hormone cortisol rises when you don’t get enough sleep, affecting your mood and making keto-flu symptoms worse.

Q. Can the keto diet lead to hair loss?

A. You may have been aware of some of the adverse effects of the ketogenic diet before starting it, such as exhaustion, constipation, and nausea. Hair loss is a common side effect of the ketogenic (or keto) diet.

Q. Are there downsides to the keto diet?

A. Fatigue, headache, cognitive fog, and an upset stomach, known as “keto flu,” are common short-term side effects. Long-term health issues include kidney stones, osteoporosis, and liver illness. Other dangers are unknown because there are no long-term trials.

About the Author

Parul holds a Masters of Medical Science in Public Health Nutrition from the University of Glasgow, Scotland, and has worked across the globe from the U.K to New Zealand (NZ) gaining her License with the Health Professionals Council (HPC, UK) and the NZ Nutrition Council. From being a Gold medalist in Clinical Nutrition to being awarded an internship with World Health Organisation (WHO, Cairo, Egypt) and Contracts with CDC Parul has had a wide spectrum of work experiences. She is very passionate about Nutrition and Fitness and holds strong to her guiding mantras ‘ Move more’ and ‘Eat Food that your grandmother can recognize’!

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