Keto Flu – Managing the Ketogenic Diet Side Effects

Many people are now familiar with the high-fat, low-carb diet, also called the 
ketogenic diet, and the benefits it offers those who need to lose a significant amount 
of weight and curb sugar and carbohydrate cravings. 

The keto diet limits starch and sugar quite severely, focusing on foods that are 
almost entirely made up of protein or fat. Some low carb diets cut out carbohydrates 
entirely, while others allow one to eat a very low number each day, such as 20 grams 
or less.

This approach to dieting places the body in a state called ketosis, during which 
stored fat is broken down and converted to carbohydrates. The latter are then used 
as fuel for energy. 

However, this type of diet has a few side effects that may be unpleasant for certain 
individuals. This set of symptoms is often referred to as the "keto flu,” and may last 
anywhere from a few days to a month. Below are some essential facts about these 
symptoms and their underlying causes.


1. Keto Flu Symptoms

Although not all individuals experience keto flu when following a low-carb diet, most 
have at least a few of the symptoms. Regardless of how many side effects a person 
experiences, however, most dissipate within five to seven days. In certain cases, 
symptoms may last for as long as a month, but this is quite rare. Most side effects of 
the diet typically begin anywhere from 24 to 48 hours after carbs are restricted and 
usually include the following:

Sugar Cravings

The earliest, most common side effect of the ketogenic diet is strong cravings for 
sugar and starch. This is particularly true if the person was formerly in the habit of 
consuming substantial amounts of starchy foods and sugary snacks on a regular 
basis. 

It is partially a physical craving, but is also a result of a reaction in the brain's reward 
center when it is deprived of endorphin-producing foods such as chocolate or other 
high-carbohydrate “comfort” snacks. This symptom is typically one of the first to 
cease after a few days of following the ketogenic diet, after which sugar cravings 
usually plummet.

Dizziness

Dizziness is a very common symptom of ketosis, and although it may be a bit scary, 
this side effect is almost always harmless. It has to do with the body's electrolyte 
balances, which are temporarily disturbed by the low-carb diet. Although it is 
harmless overall, those who experience this symptom should not drive or participate 
in any activity where good coordination is needed, as this is the best way to avoid 
any potential injuries resulting from losing one's balance or falling.

Poor Concentration and Focus

Poor concentration and focus, more commonly referred to as "brain fog," is simply a 
lack of focus that occurs when the brain is no longer being fed raw sugar and simple 
carbohydrates on a regular basis. This symptom usually only lasts until the body is 
firmly into ketosis, after which it will break down fat stores with which to supply the 
brain with energy.

Irritability

Virtually all diets are associated with some level of irritability as a side effect. 
However, this symptom is very short-lived when one is following the keto diet, and 
usually ceases within three to four days.

Nausea

Nausea is also a common side effect of the ketogenic diet, and is similar to the 
nausea felt when one becomes very hungry after not having eaten for a long period. 
This is because the body is feeling the deprivation of carbohydrates and sugars. 
Once again, after the body has reached the state of ketosis, this symptom abruptly 
stops.

Stomach Cramps

Stomach cramps are a less common side effect of the ketogenic diet, but are 
sometimes experienced on and off throughout the first week after carbs have been 
restricted.

Muscle Soreness

Muscle soreness is a symptom that affects approximately 50 percent of those 
following the ketogenic diet. Although it feels similar to the muscle soreness 
experienced after a vigorous workout, it usually comes and goes in a random pattern. 
This symptom may continue for up to a week or longer, depending on various factors.

Insomnia

Insomnia is a very common side effect of a low-carb diet, and most individuals who 
follow this diet usually experience this symptom for up to a week or two. Sleep is 
closely linked to how one's metabolism functions, and because this balance is 
temporarily disrupted when a person begins the ketogenic diet, his or her sleep 
hormones may also be affected.








2. Understanding Why Keto Flu Occurs

It is a good idea to acquire a thorough understanding of why keto flu occurs, as this 
helps one to understand the root of each symptom and why such side effects are not 
permanent.

When the body switches over to burning stored fat for energy, which is the case with 
a low carbohydrate diet, it means it must go through keto-adaption. This is also 
referred to as beta-oxidation, and it is an easier process for some people than others. 
This is because a person may be what is called “metabolically flexible,” or he or she 
may be entirely inflexible with regard to metabolic changes. 

Metabolic flexibility is another term that refers to how well a person will adapt to his or 
her body using an alternate fuel source, such as the switch from carbs to fats that is 
associated with the ketogenic diet. One's level of resistance to this change typically 
determines the length and severity of his or her symptoms when beginning a low-
carb diet. 

Those with little or no metabolic flexibility almost always experience ketogenic diet 
side effects as their bodies adjust to this change. Although there are no specific 
markers for whether or not one will be flexible with regard to this process, it is 
believed that genetics may play a role. 

Whether a person adjusts well to this change or not, when carbohydrates are 
restricted, the body goes through three primary metabolic changes. These changes 
are what lead to the common keto flu symptoms. 

Sodium and Water are Flushed Out 

When carbohydrates are restricted, the macronutrient responsible for the highest 
release of insulin is triggered. Insulin transports sugar and simple carbohydrates into 
cells where they can be used as fuel. In addition, this macronutrient has a specific 
effect on the kidneys. When insulin transmits information to the cells to let them know 
excess energy is available, it also sends signals to the kidneys to preserve water and 
sodium.

Sodium is released from the body when insulin levels drop, and it takes plenty of 
water with it during this process. For this reason, many people lose up to ten pounds 
of water weight in less than a week when following a low-carb diet. 

This is also true of glycogen, which is sugar in its stored form. Water levels and 
glycogen are directly connected as well, as it takes approximately three grams of 
water to store one gram of glycogen.

During the first day of a low-carbohydrate diet, a person's main energy source 
becomes the glycogen stored in his or her muscles and liver. This typically results in 
a pound or a pound and a half of water loss the first day. 

The combination of low insulin levels and glycogen loss causes the elimination of 
enough sodium and water to lead to gastrointestinal issues, headaches, muscle 
cramps, nausea, and dizziness, which are some of the most common keto flu 
symptoms, as previously mentioned. As one might suspect, replenishing minerals 
and fluids is a good way to alleviate all or most of these symptoms, at least to some 
degree. 

Although consuming eight, 8-ounce glasses of water per day is believed to be 
adequate water intake for healthy adults, those following a ketogenic diet may wish to 
up their water intake substantially, particularly during the first seven to ten days of the 
diet.

Decreased T3 Thyroid Hormone Levels 

Numerous research also indicates that thyroid function is linked to carbohydrates to 
an even greater degree than caloric intake. One study found that carbs are an 
essential regulatory factor in T3 production. 

T3 is the most powerful thyroid hormone made by the human body, and restricting 
carbohydrates to zero grams can lead to a decrease in this hormone of as much as 
47 percent. T3 is five times more biologically active than T4, the latter of which is the 
thyroid hormone the human body produces in the greatest quantities. 

When T4 levels are abnormally high, they reverse the effectiveness of T3 levels, 
which can lead to lower physical stamina. Therefore, allowing these levels to 
plummet is not recommended. However, this is thought to be exactly what happens 
when carbohydrates are restricted. 

Nevertheless, it is important to understand that this does not mean any permanent 
change is taking place in the person's thyroid gland. In fact, there is no evidence to 
suggest that following a low-carb diet permanently affects the thyroid gland in any 
way. Rather, it merely leads to the initial symptoms associated with carbohydrate 
restriction.

Increased Cortisol Levels 

When a low-carbohydrate diet is followed religiously, it triggers a “starvation” 
response in the body. This leads to the need for increased energy levels, which is a 
problem the body solves by releasing a deluge of stress hormones, including cortisol. 
Not surprisingly, several negative side effects are associated with this release of 
cortisol, such as irritability, confusion, lack of energy and in some cases, muscle 
pain.

Interestingly, research indicates that exercise has no impact on the increased cortisol 
levels associated with the first phase of a low carbohydrate diet. The most common 
symptoms associated with high cortisol levels are insomnia, poor quality sleep and 
irritability. 

Once a person's body has adapted to the ketogenic diet, cortisol levels decrease. 
This is because stored fat becomes the body's primary source of energy. When 
stored fat is being burned regularly, the body no longer craves sugar and starch. 
Simply put, the person's body has adapted to a new metabolic function and the 
symptoms outlined above fade away and do not return. 


3. Managing Your Symptoms

The best way to get a handle on your keto flu symptoms is to look at where they 
might be coming from. There is often an easy resolution for many of these symptoms 
and side effects to be more comfortable now. But don’t forget – the keto flu 
symptoms only last a short period of time. Once you get past them, you will feel 
amazing and on your way to a permanent lifestyle change.

Here are some helpful tips for managing these symptoms:

Take a Magnesium Supplement – This is helpful for many of the side effects of the 
ketogenic diet, but especially when you suffer from insomnia. Take this supplement 
at night before you go to bed, even if you take the rest of your supplements earlier in 
the day.

Replenish Your Electrolytes – One of the main reasons you feel dizzy or sluggish 
during the ‘keto flu’ period is because your body is going through a lot of your 
electrolytes. Focus on replacing the main ones, including sodium, magnesium, and 
potassium. 

Get More Sodium – If you still feel lightheaded or just not yourself, focus on getting 
more sodium into your diet. Easy ways to do this are by drinking a little pickle juice 
when you feel lightheaded, or having some broth.

Make Sure You Have Enough Fat – You should also focus on getting enough fat in 
your diet, as this is a high-fat, low-carbohydrate diet. Choose healthier fats like 
coconut oil, olive oil, and avocados.


4. Moving Beyond the Keto Flu

Restricting carbohydrates from one's diet is usually a healthy option, as most of 
today's modern carbs are nothing more than processed starch products or junk food 
filled with excessive amounts of sugar. Such foods cause inflammatory responses in 
the body that can lead to a host of illnesses and disorders, particularly later in life. 

For this reason, fighting through a few initial symptoms associated with keto flu is 
usually well worth the results of a slimmer body, less body fat and ultimately, a 
healthier lifestyle.

Fortunately, because the symptoms of the keto flu last only five to seven days in 
most cases, they have no long-term harmful effects. In the rare case that one 
experiences these symptoms for a month or longer, it may indicate that person is 
extremely metabolically resistant and the low-carb diet is not a good choice. 

However, it is estimated that only approximately ten to 12 people in every 250,000 
have this extreme type of metabolic resistance. As always, anyone who plans to 
begin a new diet or exercise program should speak to a licensed medical 
professional in advance about his or her intentions.

