Ketogenic diets have become a popular way to lose weight and that isn’t terribly surprising.
Essentially, this type of diet is a variation of low carb dieting, where your carbohydrate consumption is so low that the body is burning fat for energy, instead of carbs.
Doing so produces ketone bodies, which is where the diet gets its name (1).
Ketosis is appealing for weight loss because you are burning fat and also because the diet tends to reduce hunger (2). At the same time, the diet has also been linked to other benefits for health, such as lowering insulin levels (3), improving cholesterol and lipid profiles in the blood (4), along with potentially decreasing risk for heart disease, epilepsy and cancer (5,6).
One of the challenges with this type of diet is figuring out when you are actually in ketosis. In most cases, you can just follow a ketosis diet. But, individual people do vary in the carb intake needed to reach ketosis, which can complicate matters. In particular, some people need to lower their carb intake further than others to enter into ketosis.
With that in mind, this post offers 9 important signs of being in ketosis. Watching out for these signs can help you figure out whether your diet is right to put you in ketosis and keep you there.
1. Weight Loss
Weight loss is probably the simplest example out of the various signs of being in ketosis. This is also the reason that many people turn to ketogenic diets in the first place.
As with any diet, the main way to lose weight via ketosis is to stick with it. For many people, this isn’t a problem. However, some people do find the side effects of the diet intolerable. If that’s the case for you, you may want to look into a different type of healthy diet and lifestyle instead.
Additionally, weight loss may be one of the signs of being in ketosis, but on its own this isn’t enough to prove you have reached ketosis.
After all, a low carb diet in its own right will help you to lose weight, as will simply restricting your calories.
2. Bad/Fruity Breath
One of the most obvious signs specifically related to ketosis is your breath. In many cases, people report that their breath ends up smelling fruity and unpleasant overall. This might not be something you notice yourself but the people around you will certainly be aware of it.
Bad breath might not be a good outcome but it is a relevant one.
The side effect comes from the ketone bodies that are being produced. As such, it is a pretty reliable indicator of when you are in ketosis (9).
In many cases, the issue will go away as you progress on the diet, so you probably won’t have to deal with it forever.
Thankfully, bad breath is fairly easy to get around.
For example, you can brush your teeth more regularly than normal and rely on gum to mask the smell.
Just make sure you check the labels for anything you do consume to make sure you aren’t inadvertently having extra carbs.
3. Increased Ketones in Your Breath
The bad breath aspect of ketosis mostly comes from acetone (10), which means that you can easily test whether you are in ketosis.
In particular, there are many acetone breath analyzers, including some that are developed specifically for a ketosis diet. This can be a powerful way of keeping an eye on your ketosis overall (11), especially as it is a more practical indicator than bad breath.
By its nature, a breathalyzer is simple to use and convenient, which is another appealing factor.
In many cases, these tools will also connect to software on your computer or phone, allowing you to monitor changes over time. This can be especially relevant if you’re on a ketogenic diet and can help you figure out what practices work best for you.
4. Ketones in Your Blood
One of the key hallmarks of ketosis is the production of ketone bodies, so it shouldn’t be a surprise that these are connected to many of the signs of being in ketosis.
Typically, ketosis is defined as being between 0.5 to 3.0 mmol/L of ketones, although the precise definition varies depending on the source.
This method of testing is more accurate than measuring the ketones in your breath, although it is also more expensive and can be a hassle. In particular, you might end up paying around $30 for the kit, plus $5 or so for each test.
That can add up fast and you need to prick your finger to get the blood needed.
Nevertheless, this technique is commonly used in hospitals and in research, so it tends to be fairly reliable (12).
5. Ketones in Your Urine
A related sign of being in ketosis is the levels of ketones that are in your urine. As a way of testing ketosis, this method tends to be cheaper and simpler than testing your blood and even your breath.
However, this technique also isn’t as reliable (13), so it should be used with caution.
6. Problems with Digestion
In some cases, people also find that a ketogenic diet can cause problems with their digestion, particularly in the form of diarrhea or constipation.
For the most part, this isn’t really connected to ketosis itself.
Instead, this tends to be related to dietary changes. After all, a ketosis diet can mean that your food choice is radically different than it was beforehand. This means that you may need to pay close attention to what you’re eating.
Often, the problems with digestion will decrease over time, as your body becomes used to your new diet.
Some people also recommend that you look for a probiotic to help support gut health while you’re on this type of diet.
In particular, probiotic supplements may be relevant, as there are some options that are low carb.
Doing so may be especially significant because a ketogenic diet tends to be fairly low in fiber and resistant starch and this can contribute to poorer gut health overall.
7. Low Energy and Fatigue
Another unfavorable indication of ketosis is fatigue and tiredness.
For the most part, this tends to be a short-term side effect, although it can be extremely frustrating when you experience it.
This pattern is completely natural because with ketosis you are switching from carbs as an energy source to fat. It can take your body time to adjust to this change, especially if you had a fairly high amount of carbs in your diet previously.
In some cases, it may take a month, or more, to adjust to this change – during which time you may find yourself low on energy. Likewise, you may have other related symptoms, such as being irritable and struggling to focus, as these are often issues with low energy.
There is no way to bypass this issue completely but some people find that electrolyte supplements help, especially as early weight loss is often in the form of water. Key electrolytes to consider are sodium, potassium and magnesium, especially if you don’t get a lot of these in your diet.
8. Sleeping Issues
Another indication that you are in ketosis can come from sleeping problems.
Early on many people experience problems with going to sleep or with staying asleep.
This is also connected to the dramatic change that you go through when you switch to a ketosis diet. Simply put, it takes your body time to adjust and this can affect many aspects of your life, including your ability to sleep.
Unfortunately, this pattern makes the issue with low energy and fatigue even more significant.
However, it is another side effect that doesn’t last for a long time. Instead, your body will adjust to ketosis and that adjustment will mean that many of the signs of being in ketosis decrease or vanish altogether.
9. Improved Energy and Sleep
This might seem contradictory but ketosis can also result in improvements to your energy levels and sleep patterns. Specifically, these improvements occur once you have been on the diet for a while.
So, you may struggle with energy and sleep early on but once your body has adjusted to the change in energy source, both of these areas tend to show considerable improvement.
In fact, some people swear that their energy levels and sleeping patterns are better on a ketosis diet than they were beforehand. Likewise, ketosis and low carb diets seem to improve brain function (16,17).
Ketosis can seem scary because of the various side effects, especially when you first start this type of diet. Nevertheless, this is a healthy diet and a powerful way of losing weight.
Plus, for the most part, the signs of being in ketosis become less significant as you progress with the diet. So, it is worth sticking to the diet even if it seems incredibly difficult at first because it will become easier.
Personally, I recommend that you follow the diet for at least a month before you evaluate whether or not it is right for you. It can take that long for your body to adjust to the changes. Once it has, the side effects should dramatically decrease.
The strength of the side effects will also be connected to your diet beforehand.
For example, if you already consumed a low-carb diet, the change you're asking of your body isn’t nearly as dramatic. As such, the side effects are likely to be less significant. Likewise, you may experience more side effects if the diet involves a considerable change to the food that you’re eating.
Despite differences between people and their situations, simply following a ketogenic diet should be enough to keep you in ketosis most of the time.
However, if you’re uncertain or worried about the specifics of your diet, relying on either blood or breath tests can be an effective way to keep an eye on your ketosis.
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