What are Exogenous Ketones

By Siim Land

If you’ve followed the ketogenic diet then you may have already heard about exogenous ketones. They’re quite mysterious and not something you could find in regular supplement stores. What are they and how you can use them to improve your health and performane?

What are Ketones

Ketone bodies are biochemical compounds that get produced by the liver to generate energy for the mitochondria. This happens when the liver glycogen stores get depleted and an alternative fuel source for glucose is needed. Our body is an incredible bioenergetics power plant and has created a very efficient back-up fuel tank for this.

Beta-oxidation is the process that takes place in the Krebs cycle, during which fatty acids get converted into a ketone called acetoacetate, which goes further through ketogenesis, creating 2 additional ketone bodies (1) Beta-hydroxybutyrate (BHB), which is the preferred fuel source for the brain and (2) acetone, that can be metabolized into glucose, but is mainly excreted as waste. BHB is not necessarily a ketone body, but still functions like one and can be converted to energy via acetyl-CoA.


This happens endogenously, meaning that it originates from the body’s internal source. All humans, even sugar burners go through this process every single day to a certain degree. In a fasted state, the liver uses more fatty acids at the expense of glycogen. The difference is that when you’re keto-adapted your brain and muscles actually accept ketone bodies as a primary fuel source. On a carb based engine you’re mainly excreting them via “keto breath” and urine, which explains why after you ditch the carbs you’ll have a slightly smelly mouth and bathroom breaks accompanied by the odor of acetone.

Exogenous Ketones

Exogenous ketones are nothing else but ketone bodies manufactured into the form of a nutritional supplement, hence the name – originating from an external source. Most of the products are based on BHB or medium-chain triglycerides (MCTs). The reason for using BHB is that it can be utilized directly by muscle tissue.

When you consume exogenous ketones, you promote the body’s production of ketone bodies and provide instant energy that can be put into use faster and more efficiently. Within a few hours, your blood ketone levels will rise and hypothetically you’ll be in ketosis, even when you’re eating a higher carb diet. This happens because of ingesting pure BHB and MCTs, which to a certain extent circumvents the majority of the beta-oxidation process. Your body doesn’t have to be as efficient with ketogenesis or its utilization but will simply get access to a surging source of free fuel.

In a nutshell, exogenous ketones are nutritional supplements that make you more ketotic due to the soaring rise of ketone bodies that the body can readily begin to use as energy. I would imagine them being the ketogenic equivalent of dextrose, which is powdered pure glucose, with the exception that BHB is a much higher quality fuel source that will burn for a lot longer and gives immense energy instantly.

The Miracle Biohack?

So, you take these exogenous ketones and you’ll be in ketosis at a snap? Sounds great and too good to be true. To a degree, this also means that you can remain ketogenic even while consuming a high carb diet. You take the supplement, which raises your blood ketones and decreases blood sugar, while at the same time eating some glucose.

By the same token, it won’t put you into ketosis, per se. While you’re under the influence of the supplement, you’ll be in a ketogenic state, which means that the body will be using fat as a viable fuel source. What follows are other adaptive symptoms, like increased energy, suppressed hunger, anti-inflammatory properties, neuroprotection and enhanced mitochondrial density. However, after a while, the effects will begin to diminish and your ketone levels will drop. If you’re on a carb based diet, then you won’t be in ketosis.

What makes exogenous ketones great is that they enable the body to instantly utilize BHB and fatty acids as fuel. You’ll definitely be ketotic, but if you want to get the long term benefits of ketosis then you would still need to follow a well-formulated ketogenic diet.

My Experience With Exogenous Ketones

This manufactured BHB is available in the form of ketone salts and ketone esters. Currently, the supplements that are available for commercial use are all ketone salts, whereas esters are only used in research. Ever since they were introduced in 2014, they’ve become quite popular. At the moment, there aren’t a ton of brands out there. KetoForce, KetoCaNa, Keto OS and Quest’s MCT powder are just a few.

Being quite the biohacker and an athlete, I wanted to try out these “miracle supplements” to see how they would affect how I felt and my performance. Therefore, I got access to a sample of Keto OS (kudos to Ketoisland.com).


What interests me the most is what’s inside the supplement that makes it work. For Keto OS, the ingredients are: BHB, MCT powder, Natural Flavor (not said what), Malic Acid (a natural substance found in fruits and vegetables, produced by the body to convert carbohydrates into energy), Ascorbic Acid (Vitamin-C compound). Contains milk products and is gluten free. The macros per 22 g serving are: 110 calories, 7 g fat, 1.4 g sodium, 3 g carbs, of which 2 g sugar (Malic Acid probably) and 1 g protein. The list of ingredients is quite good and keto-proof, as some poor quality MCT powders (with the exception of Quest) have dextrose in them, which is not ideal.

It’s super easy to consume – you simply dissolve it into 15 ounces of water and drink it as a shake. As far as the taste goes, then it’s 10/10. This particular sample was Orange Dream and it definitely had a slight citric flavor to it. It’s not like a sugary sports drink because of the higher fat content. There’s more texture and some nice creaminess to it with a hint of Stevia-like substance. I was very positively pleased. What I also felt was that it might be actually too sweet and stimulating for my palate. Using the entire packet in only 15 ounces of water would’ve turned it over the top. Given I’ve become so sensitive to the taste of sugar due to following a ketogenic diet, I preferred to use half a serving so that I wouldn’t explode my taste buds.

What I Experienced

What I anticipated next was how it would affect my energy levels. Before drinking the shake I had been fasting for about 16 hours and my blood ketones were at 0.9 mmol/L, which is about 80 mg/dl of blood glucose. I was already in decent ketosis where I was usually at. In the ad, it’s said that you’ll be in ketosis in less than 59 minutes. So I waited. What I experienced within the first half an hour already was a slight increase of energy. It wasn’t much different from having a decent ketogenic meal but the effects were still evident. I wouldn’t have been able to run through a wall or anything but I still felt some difference. After 1.5 hours I checked my ketones again: 1.3 mmol/L, which would’ve happened by consuming any other keto food as well.


Another thing I wanted to test was my performance. After 3 hours of taking the supplement I started working out. Full body bodyweight resistance training with muscle-ups, weighted chin-ups, handstand push-ups, kettlebell swings and vertical jumps. Up until that point I hadn’t still consumed anything else but the shake and was practically in a fasted state. Because of keto-adaptation, I was already used to not being negatively affected by the lack of calories and already do most of my workouts on an empty stomach.

What I’ll do give credit for is the feeling of increased mental focus and acuity. My brain had more energy than if I would’ve purely fasting on water. It masked the perceived feeling of fatigue that may occur sometimes and enabled me to train hard with no regrets. Did I turn into a superhuman and hit personal records left and right? No. I went in, followed my routine and hit the exercises I was supposed to do and progressed in them.

What Exogenous Ketones Would Work for Best

Overall, I was pleasantly pleased with Keto OS. It tastes great and definitely gives you the ketones they promise. The ingredients are great and you can get some great energy from them. Are they a miraculous magical supplement? No, but they’re very effective nonetheless. They aren’t supposed to be some sort of a superhuman drug either.

When I would compare how I felt on Keto OS with my everyday ketosis then I found no significant difference. If you were to give me a placebo then I wouldn’t tell much difference. However, there’s still an increase in both biomarkers and energy levels. Exogenous ketones will make the 1.0 version of you into 1.1. Would I be able to get the same results by simply eating keto food or taking MCT oil? Yes, but the impact might be small for someone who’s already well keto-adapted but it’s still there.

Exogenous ketones and Keto OS in particular would work great for people who are not in ketosis and would like to get started. It’s also very good for therapeutic use. They increase your ketone levels and may speed up the adaptation process. However, that would also have to be accompanied by following a ketogenic diet. It would also be useful to use before eating more carbohydrates that would kick you out of ketosis. This will kind of “mask” the carbs beneath the surging rise of BHB.

Exogenous ketones as a performance enhancing supplement would also work great. Ketones are actually the body’s third fuel source – jet fuel – above both carbohydrates and fatty acids. Now, if you were to combine them with some pre-workout carbs, like in the case of the targeted ketogenic diet, then you would have a much more significant response than if you were to solely follow a high carb diet. The combination of those 2 would have to resemble fusion power, which is generated by the Sun. That’s how I feel like when working out on both carbs and ketones.

If you want to read more articles about the ketogenic diet and how I use it to enhance my athletic performance, then check out my blog. I’ve also written a book about the targeted ketogenic diet in which I tell you exactly what to do and what not to.




Keto Island Position on Exogenous Ketones

I only recommend that Keto/OS should only be taken as a SHORT TERM bridging tool to help you transition into a well formulated ketogenic diet (Or better yet don’t use the product). On a side note there may be an athletic boost giving you the competitive edge performance wise. I do not and will not endorse long term use of exogenous ketones, If you are interesting in using Keto OS as a bridging tool and live in the US Buy Keto OS here.