Exogenous ketones are a popular supplement among keto dieters. They’re often promoted as a type of shortcut, a way to get into ketosis faster and to see desired outcomes sooner.
But, as with any product, there is a ton of information out there. Some of that information is accurate, while other pieces may be misleading or entirely incorrect.
In this post, we’re examining exogenous ketones in depth, including the way that they work, what you can expect and when you should use them.
What are Exogenous Ketones?
The process of ketosis produces three types of compounds: acetoacetate, acetone and beta-hydroxybutyrate (also called BHB) (1,2). These are all considered ketones or ketone bodies.
The compounds are responsible for the various advantages of a keto diet. They’re also what you focus on when you’re testing for ketosis.
A Brief Look at the Science
In our bodies, ketones are produced through the oxidation of fatty acids. There are various steps in the process, beginning with the compound acetyl-CoA. This leads to the production of acetoacetate. Acetoacetate can convert to BHB (and vice versa). Acetoacetate also converts to acetone.
Of the three types of ketone, most supplements will use BHB. There are various reasons for that choice, including how BHB effectively increases ketone levels and how it works easily in supplements.
Technically speaking, BHB isn’t a ketone at all, as the chemical structure includes two -OH groups. But, it behaves like a ketone in the body and can be viewed as one in relation to ketosis. The site Keto Source discusses the various mechanisms and implications in much more depth.
When we follow a keto diet, our bodies produce ketones naturally. These are technically endogenous ketones, although that term is rarely used.
Exogenous ketones are those same compounds but they’re produced externally. They’re consumed as part of a supplement and there are many exogenous ketone products on the market.
Most exogenous ketone products come in the form of a powder. You can simply mix it into water or add it into another drink.
These products can help you get into ketosis faster or to get back into ketosis.
Exogenous ketones refer to ketones that are produced outside of the body and consumed via supplements
When Should You Use Exogenous Ketones?
Exogenous ketones aren’t essential. You can enter ketosis (and stay there) by following a keto diet plan or simply sticking to your macros. For example, the site ruled.me has many great guides for beginners, including a 30 Day Ketogenic Meal Plan.
But, exogenous ketones can still be useful in some situations.
For Reducing Keto Flu Symptoms
The keto flu is a common issue when you first start a keto diet. It occurs as your body is adjusting to using fat as fuel. As the name suggests, you will experience flu-like symptoms, such as headaches and fatigue.
Supplementing with exogenous ketones can reduce many of these side effects, making the process much more bearable.
For Re-Entering Ketosis
To stay in ketosis, you need to be strict about your macros. Even small deviations in your carb intake can kick you out of ketosis. This can be challenging, as there are hidden carbs in many places (like salad dressings).
Getting back into ketosis again takes time, but exogenous ketones can help speed up this process. This effect is especially powerful if you're keto-adapted.
For More Flexibility
The strict nature of ketosis can be difficult for many people. Including exogenous ketones in your diet typically allows you to consume more carbs than you could otherwise, without exiting ketosis.
You still need to pay close attention to your carb intake and focus on low carb foods. But, the exogenous ketones mean that if you do slightly go over your carb goal some days, you should be alright.
For Athletic Performance
Some athletes do follow a keto diet in its entirety. Others find that they need to consume extra carbs to boost their performance. For anyone relying on those additional carbs, exogenous ketones make it easier to get back into ketosis or make it possible to remain in ketosis while consuming more carbs.
Research also shows that the supplements can promote acute ketosis. This may last for a few hours, regardless of current muscle glycogen levels (3). The process also appears to have a protective effect on muscle glycogen (4). As such, exogenous ketones may improve performance in endurance exercise.
Keto-adapted athletes can experience performance challenges for high-intensity exercise, due to the reliance on fat as fuel. This is an issue because fats metabolize slower than carbs. Exogenous ketones can help by providing an alternative source of energy (5).
For Decreased Hunger
Some research suggests that exogenous ketones can decrease appetite (6). This may be relevant for weight loss, especially for long-term keto dieters. However, the study simply compared a ketone drink to a dextrose drink, there was no control group.
The ketone drink also relied on keto esters. We’ll talk about these a little later, but most commercial products will use keto salts, not esters. It isn’t clear whether keto salts would have the same impacts.
If you’re already in ketosis, exogenous ketones can be a fast source of energy.
Exogenous ketones promote ketosis, making it easier to stay in ketosis or get back there
Exogenous Ketones for Weight Loss
A keto diet itself will help you lose weight. This is a key reason for being in ketosis and there is plenty of evidence that links keto diets to weight loss.
But, despite some of the marketing out there, exogenous ketones don’t directly contribute to weight loss. They’re simply a tool that can help you get into ketosis.
If your motive is weight loss – exogenous ketones can get you to your starting point (a state of ketosis) so that you can then take the ketogenic diet to where you want to go (your weight loss goals).
If you can already stay in ketosis consistently from your diet alone, you’re unlikely to see many additional benefits from exogenous ketones. The main advantage would be a possible decrease in hunger, although evidence for that effect is limited (7).
And, of course, you can’t just add exogenous ketones to a conventional diet and expect weight loss results. You need to focus on following a keto diet and eating nutritious food.
Exogenous ketones don’t directly promote weight loss
Types of Exogenous Ketones
There are two main types of effective exogenous ketones – ketone esters and ketone salts. Both types can raise ketone levels in the blood and help promote ketosis (8).
Ketone salts are the most common type of exogenous ketones. Here, the ketone is bound to another compound, such as potassium or magnesium.
The process allows your body to easily process the ketone, while still increasing your ketone levels.
Some people find that ketone salts are easier to tolerate than MCT oil. But, ketone salts can still cause side effects, including stomach aches.
A ketone ester is basically a ketone with an added alcohol (-OH group). This process needs to be done synthetically. The process is slightly different for BHB, as it isn’t a ketone to begin with. But, the end result is similar.
Ketone esters do have some significant issues, including a bad taste and gastrointestinal side effects. They’re mostly just used in research studies (9). Indeed, most (if not all) of the commercially available ketone supplements are ketone salts, not ketone esters.
Still, the esters do produce faster results than ketone salts, helping to quickly increase ketone levels (10). This suggests that they may become more available in the future, especially if issues with taste and side effects can be resolved.
What about Raspberry Ketones?
Raspberry ketones are often included in weight loss products. You can find them as an independent supplement too.
From the name and marketing, these products sound like exogenous ketones. But, they’re not. They don’t have anything to do with ketosis or a ketone diet. The site Perfect Keto offers more details about raspberry ketones and what they actually do.
Exogenous Ketones vs MCT Oil
MCT oil is sometimes considered an exogenous ketone as well. The same is true for other sources of medium chain triglycerides, like coconut oil.
This is because MCTs are broken down quickly, resulting in ketone production. As such, they can be a fast way to boost ketone levels. Many people take advantage of MCTs by making keto coffee, which typically includes MCT oil or coconut oil, along with other healthy ingredients.
Because MCT oil doesn’t contain ketones, it has a much lower impact on ketone levels than ketone salts or ketone esters.
Still, MCT oil is often more practical and is easier to include in your diet on a daily basis. The MCTs also offer other health benefits. If you’re already in ketosis, you probably don’t need the large ketone boost from exogenous ketones anyway. In that situation, MCT oil could be a better choice.
Ketone esters and ketone salts are the main exogenous ketones, although MCT oil has some similar effects.
Do Exogenous Ketones Work?
The simple answer is yes, exogenous ketones are effective. They also work quickly, often increasing ketone levels within an hour.
These effects have been shown through research. One study examined the impacts of ketone ester and also ketone salt drinks on a range of measures. The authors found that both types of drink decreased blood glucose levels and increased blood ketone concentrations (11).
Another study showed that ketone ester drinks were able to increase BHB levels in the blood after just 60 minutes (12).
Other research has confirmed this outcome as well (13), including studies looking into the role of ketone supplementation for disease treatment (14,15,16,17).
But, as Well and Good highlights, most of the benefits occur for people who are keto-adapted, those who have been following a keto diet for a while. If you’re new to keto, exogenous ketones can still help, but it may take days to get back to ketosis again.
Limits of Current Research
At this point, there have been relatively few studies that focus on exogenous ketones and even fewer high-quality ones. Much of the current research has also relied on animal models and/or on ketone esters, rather than ketone salts. This means that there are many gaps in our current knowledge.
There is also little information about what effect exogenous ketones have on individuals who aren’t on a keto diet, especially in the long-term.
Ketone supplements could theoretically promote some health benefits, but more data is needed before we know for certain.
Research shows that exogenous ketones increase ketone levels in the blood
Exogenous Ketone Experiences
Research isn’t the only evidence for the effectiveness of ketone supplements. Many ketone dieters have used the supplements themselves and talk about the impacts that they’ve seen.
For example, the Perfect Keto site is filled with reviews from users, who found positive results from the company’s exogenous keto supplement. That particular supplement is a flavored version that relies on BHB as the source of ketones
Mark from Mark’s Daily Apple talks about his experiences in depth, including positive and negative outcomes:
About half the time I’ll take ketones right before Sunday Ultimate Frisbee matches. It provides a discernible extra burst of speed during the game, more overall energy (I just feel like “going” more), and less soreness the next day.
His experiences are an illustration that the ketones can offer some clear advantages, particularly to people who are already keto-adapted.
Negative Exogenous Ketone Reviews
Reviews for exogenous ketones aren’t always positive. Instead, many users have bad experiences, including the following themes:
The product tastes horrible
Exogenous ketones don’t taste good. That’s all there is to it. Some companies use flavorings to make the powder more palatable. But, there’s only so much they can do. If you expect the product to taste amazing, you’re going to be disappointed.
Doesn’t have the advertised impact
Exogenous ketones do work for their intended effects. But, marketing is often misleading. I’ve seen claims that the ketones promote immediate weight loss, that they drop you into ketosis instantly no matter what and that your carb intake doesn’t matter.
None of those claims are true.
The ketones simply help with ketosis and can get you there faster. But, if you’re consuming a large amount of carbs or if you’re not keto-adapted – don’t expect to suddenly enter ketosis.
Product caused a stomach ache
This is a known side effect of exogenous ketones. The risk of side effects tends to be lower for ketone salts than for MCT oils. Even so, some people mightn’t be able to tolerate ketone salts.
Mark talks about this issue too, stating that it is something you need to prepare for.
Unfortunately yes, exogenous ketones are expensive. This is associated with how they’re created and companies can’t easily drop the price.
The products can still be worth the price if they suit your needs. But, they mightn’t always be the best choice.
Sellers are trying to recruit or are excessively promoting products
This is simply because some companies are MLMs or have an affiliate program. When this happens, some promoters (not all!) end up being pushy or making unrealistic claims.
As such, it’s important to take a step back and look at the product objectively. Consider your goals as well. Are exogenous ketones right for you?
None of these issues mean that exogenous ketones are bad. More than anything, they illustrate that you need to be realistic about your expectations.
Most people have positive experiences with exogenous ketones – as long as their initial expectations were reasonable
Should You Use Exogenous Ketones?
Exogenous ketones aren’t essential for a ketosis diet and they won’t promote weight loss on their own. But, they can be useful if…
- You need more flexibility in your diet
- You’re entering ketosis for the first time
- You’ve dropped out of ketosis
- You’re a performance athlete
- You need extra energy
As always, you’ll need to pay attention to your own body. Each person is different and may experience individual outcomes. You may find that exogenous ketones are effective for you and make a keto diet much easier. But, you could also find that they don’t help or give you side effects.
The best way to know is simply to try them out while keeping an eye on your ketone levels and any side effects.
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