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10 Side Effects You Should Be Aware of When Trying a Ketogenic Diet


minute read

April 15, 2018

Learn about common side effects associated with a keto diet, such as the keto flu. Addressing ways to monitor and combat ailments that may pop up during your adaption phase.

Keto side effects

Starting a new diet or lifestyle can be a tremendous step in the right direction when it comes to taking control of your health. The reality is that that the Keto Diet, as with any diet, has different effects on different people.

As you start off on your Keto journey it’s important to give your body time to adjust.  The key factor in getting your body keto or fat-adapted (used to running on healthy fats instead of on glucose fuel from carbs), is to put in those first few weeks – so you can kick start your way into ketosis.

These first few weeks can be a challenge, but one thing to ease anything you may be experiencing is to educate yourself on potential side effects, so you know what is normal, and what’s not, and how to address these symptoms as the potentially arise.

1. Keto Flu

Keto Flu is perhaps the most common and also most all-encompassing ailment that people experience while transitioning towards becoming keto-adapted.  There are a variety of symptoms but many only experience one, two or none at all.  The keto flu can last from a few days to a few weeks depending on the person.

What is the Keto Flu?

The Keto Flu is the body’s response to carb restriction, and can manifest in many ways.  On average the Keto Flu will only last about a week and can begin with symptoms as early as the first couple of days when you begin to restrict your carb intake.

Keto Flu symptoms may include:

  • Dizziness
  • Sugar cravings
  • Low in energy
  • Brain fog
  • Stomach discomfort
  • Muscle soreness
  • Nausea
  • Cramping
  • Insomnia
  • Bad breath
  • Irritability

These may sound intense, but many only experience a few symptoms and some people don’t experience any at all.  Everyone is different so it really depends on the individual’s metabolism as they change diets.

What is the cause of the Keto Flu?

Unlike other flus, it is not caused by a virus.  Instead, it’s your body’s response on a cellular level.  When your body is adjusting to your new diet, it no longer needs so much insulin.  Therefore, when your body’s insulin levels drop, sodium and water is released – flushed out as “water weight” but also seriously depleting your hydration levels as well as minerals in your body, making you feel unwell. 

Other causes of these keto flu symptoms could include increased cortisol, and a flux of our T3 thyroid hormone.  We will touch on these topics more in depth in our Go Deep section here.

How do we prevent or treat the Keto Flu?

A lot of the symptoms you will read about in this section about side effects are directly related to the depletion of water and minerals – so your best way to combat these negative effects are to drink plenty of water, and increase your consumption of sodium, potassium and magnesium through diet or supplements. You can find more infomation about supplementing electrolytes in our Ultimate Keto Supplement Guide.

2. Frequent Urination

As your body no longer stores glucose as glycogen, all the water molecules stored along with the glycogen in your liver and muscles are shed.  So, don’t be surprised if your trips to the bathroom increase – as this is a side effect of being in ketosis.  With that said, it’s important to stay hydrated to replace this water, and supplement with electrolytes and other important minerals to minimize overall symptoms.

3. Dizziness & Fatigue

Since your body is shedding a lot of it’s excess water, it also means some good stuff gets released with it.  Yes, we are talking about all the vital minerals like magnesium, potassium and sodium.  You can take active measures to decrease your susceptibility to these symptoms by increasing your intake of foods naturally high in potassium.  Beyond that, it’s still important to supplement your diet with sea salt while on a Keto diet as well as oral magnesium.

Read more about supplements here, and remember to check with a physician - especially if you have any kidney problems.

4. Headaches

While adjusting to a new diet and getting into ketosis, some people report experiencing headaches. This is usually to do with a lack in minerals including sodium.  To determine if it is in fact a loss of sodium, you can drink a glass of water with 1/4 teaspoon salt, and see if the symptoms subside in 20mins.

Additionally, it is also worth noting that a lot of headaches can be associated with mild dehydration, so monitoring your water intake is key.  Beyond water, making sure your salt and electrolyte levels are maintained is going to be key in avoiding many side effects during your keto-adaption process.

5. Low Blood Sugar

Hypoglycemia is a common side effect experienced by many while starting off a Ketogenic diet.  This can be challenging for people who were previously eating a high-carb diet.  Low blood sugar can be a result of your body stabilizing its insulin during this transition.  If your body was used to producing a certain amount of insulin throughout the day to match a high level of sugar or carbs, and then suddenly your sugar intake drops off, this can result in short term low blood sugar.  Symptoms can include feeling shaky, hungry or tired but these should subside over time.

6. Cravings

When adjusting to a new diet it’s common to encounter some strong cravings.  While you are transitioning to become keto-adapted these cravings may intensify, as your brain will receive signals if you are experiencing low blood sugar therefore triggering a panic response that you need immediate energy – in the form of a sugar craving.  As you begin to produce ketones for energy these responses and cravings should subside.  The good news is that in the long run, you can expect to have a reduced appetite and cravings for sugar as well as other refined foods.

7. Constipation

Your body will be adjusting to a change of diet, which can lead to irregularity including constipation.  This can be caused by dehydration as your body gets rid of excess water.  One way to treat this is by increasing your intake of fiber through vegetables high in fiber, making sure you are rehydrating with plenty of water and also paying attention that you are getting enough salt.

8. Muscle Cramps

Some people experience leg cramps or other muscle cramps, which can be directly linked to a loss of minerals – most commonly magnesium.  To treat these cramps many find it helpful to take a slow release magnesium tablet while starting off a keto diet.  Additionally, staying hydrated by drinking sufficient amounts of water as well as consuming enough salt can also be effective in avoiding uncomfortable leg cramps.

Make sure to check with a doctor before taking any oral supplements – especially if you have a history of kidney problems.

9. Diarrhea

Unfortunately this can be a side effect of a low carb diet, yet it’s usually resolved in a matter of a few days.  This can occur as you find your balance on a new diet – especially if you are compensating with an increased amount of protein.  It’s key to make sure you’re consuming enough healthy fats while transitioning to a low carb diet as to avoid loose stools.

10. Racing Heart

Some people report experiencing heart palpitations or a racing heart when starting out a keto diet, or even once keto-adapted. This can be a side effect to a low carb diet, but it’s also thought to be more common for people who typically experience low blood pressure.  There are a few factors that can be attributed to this side effect:

  • Electrolyte imbalance or deficiencies.  It’s important to check for dehydration, lack of salt, minerals – magnesium and potassium rich foods can be excellent at combating this issue.
  • Nutrient deficiencies – which can be treated with a multivitamin, with upper allowance on zinc and selenium.  Magnesium supplement, bone broth & mineral water can also be helpful in treating these symptoms.
  • Hypoglycemia can also be a factor, coupled with insulin resistance – lowering carbs may trigger people going hypoglycemic.  Timing meals, eating regularly and frequently throughout the day, as well as monitoring your protein and fat ingestion can be a good ways to stabilize this reaction. 
  • Protein levels can also be a factor for some people – as everyone’s body varies, some may require a slight increase in protein levels in order to accommodate physical activities.  If you suspect it may be a lack of protein you can start by adding 5-10g of additional protein to every meal. 
  • Reaction to coconut or MCT oils.  Some people experience a racing heart as a reaction to excessive oil consumption.  Therefore, it’s important to start off slowly with these oils, and slowly increase the amount you ingest.  Other sources of healthy fats can also be used such as butter, olive oil, ghee, and other animal fats. 

General notes on monitoring and treating side effects:

  • ‍Drink enough water – stay hydrated!
  • Explore electrolyte replacements
  • Look into supplements to replace lost minerals - see our Ultimate Keto Supplement Guide here
  • Monitor your protein levels

Many of these side effects are either preventable or treatable, so the main thing is to stick with it, listen to your body, read up on what you’re experiencing and be patient!

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