The Side Effects of Keto Diet

Keto Side Effects Guide

It seems that everybody is raving about the high fat, low carb approach to lose weight known as the ketogenic diet. When you adhere to a keto diet, the body undergoes a metabolic state called ketosis. It becomes more efficient at breaking down fats.

But like any diet, there are possible keto side effects when you follow this regimen. Many health experts give warnings to people against following it entirely, as it can cause potential health risks and unpleasant side effects. The diet is also not sustainable. Some keto proponents even admit that if it is not followed correctly, the results could be the opposite(1).

Short-Term Keto Side Effects

There are many short-term side effects that people who are into keto may feel evident at the beginning of their diet. And they are more obvious for those who started their diet fast initially. The most common side effect is hypoglycemia, and here are some of its noticeable signs:

  • Sweating and chills
  • Lightheadedness and shakiness
  • Tachycardia
  • Confusions, irritability, and anxiety
  • Hunger
  • Fatigue
  • Frequent urination
  • Excessive thirst

In addition, patients may also experience low-grade acidosis and constipation. However, these keto side effects are only temporary, and it will improve as you continue with the diet because the body adapted to the diet and found it’s a new way to source energy.

Alteration in Blood Composition

There are many changes happening in the body when one is into a keto diet. Because of the changes in the dietary composition, the body goes into adaptive mechanisms to handle the reduced intake of carbohydrates. This includes changes in blood composition. When the body has reduced its carbohydrates intake, it goes into two metabolic processes: ketogenesis and gluconeogenesis.

Gluconeogenesis is the natural production of glucose by the body from glycerol, lactic acid, and amino acids, glutamine, and alanine. When the production of glucose in the body drops and can no longer cope up, it will switch to ketogenesis. This process produces ketones, which is an alternative source of energy.  

As a result, there is an increase in the levels of cholesterol and lipids. Compared to normal levels, there is a 60% increase in lipid levels and a 30% increase in cholesterol.

It can be a health concern for patients who have to monitor their cholesterol levels. They need to make slight changes in the diet, like changing the source for polyunsaturated fats to saturated ones. For some, it may be necessary to adjust the ketogenic ratio and the proportion of protein and fat to carbohydrate ratio.

Long-Term Effects

When the keto diet was first conceived, it was meant to treat severe epilepsy in young children and infants(2). It is an intervention diet that is intended to be administered for only a short period and under the management of health professionals. Nowadays, this diet is famous for its fast weight-loss effect and is used as an alternative low-carb diet.

To reach ketosis, the individual has to switch to a metabolic state that uses fat as an alternative fuel source for the body to replace glucose. When there is not enough glucose, the body compensates for the nutritional deficiency with ketosis. But it is not all fat burning that is happening here because the body is also breaking down muscles (protein) to make up for the glucose deficiency. Here, the long-term effect of a keto diet is a decrease in lean body mass. This means that it will be harder for the body to lose weight after the diet as it will gain more fats than muscles.

For the body to achieve true ketosis, it needs to have 80-90% of calories from fat, which can be challenging. The diet is not only low-carb but also low in protein. The plate of a person on a keto diet should contain coconut oil, fatty meats, avocado, gravy, and few carbohydrates. While the amount the latter varies with individuals, in keto, it should be around 25 to 30 grams (one medium apple).

If the body does not go into true ketosis, the saturated fats will not be broken down into a fuel source. Instead, it will have the opposite effect. The increase in eating animal fat and butter will lead to a rise in LDL, cholesterol, and triglyceride levels.

Another long-term effect of the keto diet is a deficiency in vitamins, antioxidants, minerals, and fiber. Without enough fiber, the body will have GI issues, including bloating and constipation. It will also deprive the body of the gut microbiome that is vital for reducing inflammation and immunity.

Keto Side Effects in Adults

For adults who are on keto, the most common effect includes weight loss, an increase in levels of triglycerides and cholesterol, constipation, and bloating. In women, the result of low carbohydrate is twice stressful. It can cause amenorrhea, where there is no menstrual cycle for three or more months and other abnormalities in the menstrual cycle.

Dangers of Going Keto

The Keto Flu

The most common side effect when you are just starting the diet is known as keto flu. This is a consequence when the body is adjusting to the low-carb state. When the carb intake is low, the body adapts by switching the energy source to ketones instead of glucose. Once the body reaches a metabolic state called ketosis – that’s when you know that the diet is working.

However, you may not feel great because you will experience the symptoms of keto flu that includes lethargic feeling, weakness, headache, and irritability. Others will also experience nausea, vomiting, and constipation. The body will also remove the unused ketones through frequent urination that could lead to dehydration and other flu-like symptoms like muscle soreness, dizziness, and fatigue. There could be an inevitable loss of electrolytes with more frequent urination that can exacerbate the symptoms.

Keto Diet Diarrhea

When you are on a keto diet, you may find yourself running to the bathroom more frequently than necessary. Most people who are on a diet call it keto diet diarrhea. Whenever you cut out certain foods from your regular food intake, an imbalance occurs. Because of this, you may experience tummy troubles.

The high-fat content of the keto diet takes a bit of work to be broken down, primarily if the body is not used to metabolizing the massive amount of fats. If the body is not able to burn all the fats, it will naturally try to expel it. If you consume too much fat, the body will not be able to keep up with its breakdown and absorption.

When they are unconsumed, it goes to the intestines and colon. In consequence, it pulled in more water to help dispel it, which results in watery diarrhea.

Reduced Athletic Performance

New research made on the keto diet suggests that it can help endurance athletes boost their performance. But for those who are involved in high-intensity and short-duration sports, they may see a decline in their performance.  

The reason is that keto diet affects the metabolism of anaerobic energy. In sports, the 100-meter sprint and triple jump depend on this body process. To explain it clearly, it is the same metabolic process that we use when we get up the stairs. Keto diet affects this energy system that fuels the body to climb the stairs.

People who are on a keto diet reduced their athletic performance in many activities that depends on anaerobic systems for energy. Consequently, it can have performance implications on athletes who are into short duration or high-intensity sports and activities.

Weight Regain

The restrictive nature of the keto diet makes it hard to follow because people are generally prone to carb cravings. It is also an unsustainable diet plan. Although it causes rapid weight loss, the problem lies when the person stops following the diet. When they go back on carbs, they can regain their weight as rapidly as they lose it.

People who are following the diet will have a better chance of keeping the weight, but it should be long-term, which is not easy to accomplish. When they stop, the weight will come back and may lead to yo-yo dieting, which increases the risk of diabetes and fat accumulation.

When you are no longer losing weight or want to go off keto diet, you should practice adding carbs slowly into your menu and practice portion control.

Decrease Metabolism

Another consequence of a keto diet is related to a loss of muscle mass and as a consequence, a decrease in metabolism. In keto diet, you are eating more fats than proteins, which you need for muscle growth and repair. Unknowingly, you are losing weight, and the majority of it is muscle mass. If the muscle is burning more calories than fat, it will affect your metabolism.

The decrease in muscles is evident when one goes off the ketogenic diet. The first effect will be regaining the old weight back but in different proportions. Instead of more muscles, they will most likely regain more fat. This means that the body no longer has the muscle mass to burn calories and can have lasting effects on the metabolic rate.

Vitamin Deficiency

The low-carb and high-fat approach of keto diet puts limitations on some groups of food that your body needs. These include beans, whole grains, and legumes, as well as many fruits and vegetables. Many of these foods have vitamins, minerals, and nutrients that are not found in other food sources. As such, you are depriving your body of when you are on a keto diet.

Nutritional deficiency is dangerous for the body; hence, keto is not great for long-term dieting because it is not a balanced menu. When you are on a diet that is devoid of fruit and vegetables, it can result in long-term micronutrient deficiencies, which have dire consequences to your health like bone loss and increasing the risk of chronic diseases.

Kidney Damage

It is the most critical potential side effect of the ketogenic diet. In a research published in a medical journal, it’s been observed that in children treated for epilepsy with the keto diet, 13 out of the 195 subjects have developed kidney stones.

In keto diet, consuming meats, mainly processed ones, can increase the risk of having gout (the more painful type of arthritis) and kidney stones. This is because the high intake of animal proteins can make the urine more acidic and also increase its uric acid and calcium levels. When you have a combination of these compounds, you will be most likely to have kidney stones, and high uric acid can increase the risk for gout.

A keto diet is not recommended for people with kidney disease because it can be dangerous. They need a low-protein ration, which is not aligned with the keto diet.


Not all people can be on a keto diet. Like any other diet regimen, it has benefits and keto side effects. To make sure that you are doing it right, you should consult with your doctor first even if you have no preexisting health issues. You should also contact a dietitian or a nutrition professional to help you create a meal plan that you can stick to.

The diet can result in significant changes in the body’s metabolic process and other body functions. Those who have kidney disease, history of an eating disorder, high blood pressure, and type 1 diabetes should not use it for weight loss. It can be used for a short term, though, as long as it is done correctly.

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