If you're thinking about beginning a keto meal plan, chances are you've heard of this pesky thing called keto flu. But what exactly is the keto flu, do you have it, and can you cure it?
Here's your go-to guide for keto flu symptoms, along with the remedies to get you through it.
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What is the Keto Flu?
The goal of the keto diet is to transition the body into a metabolic state called ketosis through significant carb restriction. In ketosis, the body becomes more efficient at burning fat for its source of fuel and in theory, more efficient at losing weight.
However, when starting a keto diet, switching from carbs to fat as your primary source of energy can be a big change for some people and might be associated with some unwanted side effects - commonly referred to as ketosis flu or "keto flu".
We are biologically built to love and crave carbs. This is largely because these delicious carbs are quickly broken down into glucose - which is the most accessible energy source we can use.
So what happens when we don’t let our body have what it wants? Well, it can put up a bit of a fight - and sometimes throw a tantrum.
Keto Flu Symptoms
No, it's not all in your head. Keto flu is real and can feel just like the real flu - which is exactly how it got its name.
While it isn’t life-threatening or dangerous, experiencing keto flu can feel pretty difficult be it can make many people feel awful. Some may find it so bad, that it discourages them from continuing their keto diet journey.
Because all of our metabolisms can behave just a little bit differently, the symptoms and the severity of each appear to affect everyone a little differently.
Here are some of the common known side effects of keto flu to watch for:
- Mood Changes & Irritability
- Decreased Libido
- Decreased Concentration & Brain Fog
- Bad Breath
- Muscle Aches
The important thing to remember is that the side effects from starting the keto diet are temporary! Many people that push through this phase report feeling better than they ever have in ketosis.
What Causes the Keto Flu?
The medical community really can’t yet say for sure exactly what causes the keto flu - but we do have some educated guesses.
The main theories behind what causes the keto flu include:
- Carbohydrate Withdrawal
- Hormone Imbalance
- Electrolyte Imbalance
In reality, each individual may have symptoms due to one or a combination of these factors.
Carbohydrates quickly break down in your body to glucose. Your body regularly uses energy from stored glucose through a process called glycolysis - it almost always prefers this process. When you cut out carbohydrates, your body is forced to transitions from using glucose to using fat for energy through a process called beta-oxidation and production of ketone bodies.
It’s harder and takes more time to use fat for energy. Therefore as the body is in a transition phase from using glucose to using fat for fuel, blood glucose can be low - called hypoglycemia. Hypoglycemia alone can cause many of the symptoms described by the keto flu. And while most of our bodies can compensate to ensure we maintain safe levels of glucose, this can be a dangerous condition in people with type 1 diabetes or anyone on medication for diabetes.
2. Carbohydrate Withdrawal
Some science suggests that many of us may actually be physically addicted to carbohydrates.
Many people experience the same process of binging, withdrawal, craving, sensitization and overall dependence on sugar as is seen with other forms of addiction, such as alcohol. Literally the same areas of the brain that light up with drug addictions similarly light up when people eat carbohydrates. Neurotransmitters in the brain strongly associated with addictions, such as dopamine are also released when eating carbs (1,2).
Classic symptoms of a variety of drug withdrawals often involve irritability and other mood changes, nausea, lightheadedness, headaches, difficulty concentrating. Sound familiar?
Could keto flu just be our response to withdrawing from carbohydrates (ie: sugars)?
3. Hormone Imbalance
There are some theories that thyroid hormones can also be temporarily altered with carbohydrate restriction. Lower levels of T3 - an active thyroid hormone in your blood - can lead to many symptoms including fatigue, constipation, mood changes. While this is one theory that exists as a possible contributing factor to the keto flu, there really hasn’t been enough evidence to link low carbohydrate intake to subclinical hypothyroidism (3).
5. Dehydration & Electrolyte Abnormalities
Insulin is the hormone in charge of storing glucose. In order to maintain a steady state of glucose in the body, insulin rises when carbohydrates are consumed and maintains lower levels during times of fasting. When carbohydrates are not consumed, insulin does not rise as high after eating because there just isn’t as much glucose to store.
Because it can also affect the absorption and availability of water and electrolytes lower levels of insulin can contribute to changes in electrolytes in our body and dehydration. So transitioning into ketosis can encourage diuresis - a process where you lose sodium and water (4). Usually, these levels aren’t dangerous, but they can definitely contribute to feeling bad.
Keto Flu Avoidance & Recovery Tips: How to Keep Away from the Keto Flu
Here are some easy and proven methods to help you fight and prevent the dreaded keto flu:
1. Drink Water
As explained in more detail below, your body may be more susceptible to dehydration on the keto diet -- and dehydration can contribute to keto flu symptoms, especially headache, nausea, lightheadedness, constipation, and difficulty concentrating.
It’s expected to experience a temporary decrease in energy and fatigue when starting the keto diet. You’re literally putting yourself through major metabolic changes.
It’s natural that during the transition into a state of ketosis that your energy levels feel lower - because they are. Schedule additional time for yourself to rest while these changes take place.
Whether you’re in ketosis or not, getting adequate sleep has also been shown to lead to less cravings throughout the day which is always a positive boost for your weight loss goals (7) .
So do what’s right for your body and let yourself snooze.
3. Eat Keto Approved Foods (A LOT)
While calories are undeniably a tremendous influence on health and weight loss, some people advocate that you don’t need to worry about these on the keto diet. While this is one way of doing things, and may sometimes lead to weight loss - it’s also completely dependent on the number of calories one consumes. Eating an overwhelming number of calories more than what you burn will still lead to weight gain - regardless of whether or not you’ve gone keto.
However, you may feel particularly hungry and have strong cravings for carbohydrates when you first begin the ketogenic diet. Trying to be too strict with yourself all at once can lead to you being more susceptible to breaking your diet and overeating on the wrong foods.
So, while we do recommend considering calories on your overall keto plan it may be beneficial to allow yourself an adjustment period on the keto diet. During this time you can focus mainly on following your recommended keto macros without honing in too much on calorie consumption.
When you are hungry (or just have intense cravings for carbs) try eating more keto-approved foods to help satisfy your needs. Over time, these will become less as your body adjusts and you can begin focusing more on incorporating your calorie goals.
4. Eat Salt and Drink Electrolytes
As explained in more detail below, the keto diet may contribute to you losing some salt as well as increase the potential for dehydration. Replacing this salt may improve your symptoms, and when paired with active oral hydration can also help your body to more effectively retain fluids you’re drinking. It can also help you to feel more full and contribute to you eating fewer calories or craving non-keto foods throughout the day.
If you’re on a low salt diet for hypertension, congestive heart failure (CHF) or any other medical condition, it’s very important that you talk to your doctor for formal medical recommendations before changing your prescribed diet.
Staying hydrated and eating higher sodium contents may help improve keto flu symptoms.
Meditation offers a slew of benefits for the mind, body, and soul.
On the weight loss front, it’s been shown to be beneficial for binge and emotional eating as well as weight loss maintenance in obese individuals (8,9,10). It also offers to decrease anxiety, improve mood, and concentration. Other studies link meditation to improved heart health which is possibly due to a decrease in stress hormones in those that meditate (11).
Whatever is going on with mediation, it seems powerfully positive and like something you may want to consider if going through a difficult keto flu.
Who Will Get the Keto Flu?
The process of transitioning into ketosis can affect everyone differently. Some don’t notice much change and report feeling at their best on the keto diet almost immediately - while others feel wretched for weeks. There, unfortunately, isn’t a good way to know how you’ll feel on a very low carbohydrate diet until you try it.
When Does the Keto Flu Start?
Symptoms of the keto flu often start 24-48 hours of following the keto diet. This can vary for some, however, it usually doesn’t start after more than 7 days of strict adherence to the diet.
What does this mean? If you’re still feeling good by the end of the first week, you’ve likely avoided the keto flu all together!
How Long Does Keto Flu Last?
Once you’ve been hit with the keto flu, symptoms often resolve in the first couple weeks. However, it can last up to one month.
So what exactly is it about this diet that’s causing so many people to feel miserable? Let’s take a quick look at the theories behind the causes of the keto flu.
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