Should You Try Exogenous Ketones (Keto/OS Pruvit)?


I’m always getting asked about these famous ketone supplements. Keto/OS is an exogenous ketone supplement that people are using to lose weight, among other things.

I found very little in terms of research on exogenous ketones in humans. Exogenous ketones have been studied a bit in rats, and no one has studied them in terms of weight loss in people or in rodents. The product Keto/OS has no research behind it either, so I decided to bite the bullet and put myself on it for a week to see what would happen.

Before I talk about how that all went, let’s chat about ketones and how they work in your body.

What are ketones?

Ketones are the byproduct of fat metabolism. When you deprive your body of its favorite source of energy – glucose – it starts burning your fat for fuel.

Staying on the ketogenic diet can be tough for some people, but it can be done, and for most healthy people, it’s not harmful. And honestly, the ketogenic diet has really helped me manage my Vestibular Neuronitis that I was diagnosed since I was 5 years old.

The issue with ketosis for weight loss is that when you break ketosis, the weight will probably come back on. If you’re a person who lives to eat and not eats to live, it might not be the best weight-loss option for you.

Because a ketogenic diet is so difficult for most people to maintain, Pruvit is marketing Keto/OS by saying that you can eat a normal diet, drink Keto/OS, still go into ketosis, and lose weight when your body burns fat for energy from being in ‘ketosis’ from the supplement.

Endogenous vs Exogenous Ketones

There are two ways to achieve ketosis, which is usually defined as having blood ketone levels elevated >0.5mM.

Endogenous ketones are produced by the liver during a ketogenic state, this usually occurs when fasting or following a ketogenic diet. One must strictly follow the low-carb, high-fat diet, which can be difficult in today’s society that has a long-standing love affair with carbohydrates.

  • Endogenous = ‘Endo’ = within. ‘Genous’ = origin. Originates from a source internal to the body.

Exogenous ketones are ketones consumed through a nutritional supplement. They can deliver a state of ketosis without changing the diet.

  • Exogenous = ‘Exo’ = external. ‘Genous’ = origin. Originates from a source external from the body.

Because ketosis is a complicated animal, I recently interviewed with a leading expert in the field, Dr. Ben Connolly, ND from Cornerstone Naturpathic and he explained that exogenous ketones don’t trigger natural ketone production, meaning they don’t put you in a ketogenic state. A ketogenic state can only be achieved by the body naturally producing ketones. Exogenous ketones do, however, promote a state of ketosis, which means that blood ketones levels are elevated.

Ketone Salts and Ketone Esters

There are two main types of exogenous ketones: ketone esters (liquid), and ketone salts (powder).

Esters may produce fewer side effects than salts, but neither type seems to taste very good.

Exogenous ketones are a synthetic form of ketone bodies. They come in two forms: ketone esters and ketone salts.

Ketone salts have a sodium (Na+) molecule attached while ketone esters have a double bond (ester) to oxygen (O). They are then bound to another ketone precursor/molecule, avoiding the salt or acid load. Ketone esters can be further divided into B-Hydroxybutyrate esters and Acetoacetate esters. These different esters could give different physiological effects.

Ketones for Fat Loss?

You might have come across claims that ketone supplements burn fat and improve weight loss. We know that ketones may reduce appetite over 4 hours compared to dextrose (Stubbs et al., 2018). Curbing hunger could help with long-term fat loss.

However, there are some other issues:

1 – Ketones inhibit fat breakdown and the creation of new ketones

In another interview, I chatted with Meredith Lapp, RD who is a registered dietician at Simply for Life in Halifax. She explains that the body breaks down fat to create ketones. Yet, it needs to prevent excessively high ketone levels (ketoacidosis). Hence, ketones limit the breakdown of fat (lipolysis) and thus their own production (ketogenesis) (Taggart et al., 2005Balasse and Neef, 1975Mikkelsen et al., 2015Pinckaers et al 2017Evans et al., 2017Leckey et al., 2017Stubbs et al., 2017Harvey et al., 2018).

The higher the ketone levels, the stronger the effect. This means that exogenous ketones actually prevent body fat from being used (Taggart et al., 2005Mikkelsen et al., 2015Leckey et al., 2017).

2 – No studies in humans

There are currently no short-term or long-term studies that evaluate how exogenous ketones fat loss or weight loss. I only have mechanistic evidence, as discussed in the 1st point.

3 – Ketones are calories

Since ketones are used as a fuel source, it stands to reason that they contain energy.  Ketone esters should have around ~4.8 to ~4.9 kcal per gram 1.  

A single dose of Pruvit Keto OS contains 41-110 kcal, depending on which product you use. If you take multiple servings per day, that could add up.

4 – Appetite reduction due to ketones or nausea?

Side effects are common with the ketone formulations we currently have. They often lead to nausea and gut discomfort.

It is quite possible that exogenous ketones could reduce appetite by themselves. For example, they can reduce ghrelin, which subsequently reduces appetite. It is also possible that the reduction in appetite is due to the commonly reported side effects.

Preventing Keto Flu with Ketones?

There are currently no human studies on this topic. Any potential benefit is therefore anecdotal.

Pruvit Research and Claims

The Pruvit website lists quite a bit of research, but unfortunately it’s all on ketogenic diets, not on their actual product or exogenous ketones. And smartly, Pruvit has a disclaimer on their research page that states:

Under no circumstance is the information contained within such third party research to be used or considered as a direct, or indirect study of any Prüvit product.

Pruvit claims that Keto/OS increases focus, energy, fat loss, and strength, and helps with sleep and mood. Sounds like a miracle worker!

Regardless of what Pruvit claims, my questions are: does Keto/OS work just like a ketogenic diet, or are you just drinking (and peeing out) ketones and consuming extra calories from the supplement while you do it? 

Are exogenous (meaning: from outside the body) ketones treated the same by the body as endogenous (meaning: from inside the body, or what you body makes itself as the result of a ketogenic diet) ones? Can you really consume ketones and eat carbs and still be in ketosis?

And just because you’re peeing out ketones (measured by Ketostix), does that mean you’re actually in ketosis? The definition of ketosis is when you have ketones in your blood, not in your urine. 

Pruvit says that a urine or blood test (but face it – why test your blood when you can just pee on a Ketostick) is how you test for ketosis while on their product. I have done by a fair share of researching the ketogenic diet, mainly because I get so many client requests that want a ketogenic meal plan. The true state of ketosis involves metabolic changes that include the ramping up of many fat burning enzymatic pathways as well as an increase in the number of mitochondria in the cells. This process can take a number of weeks and is referred to as fat adaptation or keto adaptation. Unfortunately, this metabolic adaptation is not something that can be bottled or made into a powder or pill.

I also had a call with a Pruvit Ambassador to get a good, balanced view of the product and see how it ‘changed his life’. He said that Pruvit is doing research on the product that will be available ‘imminently’. He was adamant that the supplement put him into ketosis, and he uses it as an adjunct to an ‘80% ketogenic diet’. “I like wine”, he joked. Hey – I hear you! He told me:

If I were to explain it in a few words, I would say that Keto//OS is the world’s first commercially available exogenous Ketone product and it works in the human body 100% of the time.  Oh, and it makes you feel awesome and the Community is about making people Better. 

Seeing as he has clearly drunk the ‘keto kool aid’, I was raring to see for myself what would happen when I tried it.

The Keto/OS diaries

I managed to secure some Keto/OS from someone in my neighborhood, which was great, because it’s super expensive. I definitely didn’t want to spend over $200 CAD for a 30-packet order when I wasn’t sure how I’d react to it.

The dosage of Keto/OS is 1-2 packets a day. Seeing as I already eat a low-carb diet on my own (not because I’m afraid of carbs, but just because I prefer to eat a lot of vegetables), I figured I’d use one packet a day and see what happened.

Day 1

I chose to start my trial on a morning that I was seeing clients. Maybe not the best choice, since I wasn’t entirely sure that I was going to drink it and not suddenly fall to the floor clutching my throat or barf or something embarrassing like that. I skipped my daily coffee because I really wanted to see how the Keto/OS was going to affect me. I weighed myself and was ready to go. Let’s burn some fat! I thought.

My first client of the day watched me sympathetically as I downed the milky white, cloyingly sweet orange-flavored drink, wincing with every gulp. The sweetness was out of control – maybe to hide the flavour of the ketones?

Interestingly, the orange flavour of Keto/OS has 110 calories; the chocolate flavor, only 50.

Anyhow, 30 minutes later, I felt fine. I started to get a headache, which never left me the entire day, but otherwise? I felt normal. I felt no effects in terms of appetite suppression – in fact, after a huge Whole Foods salad bar lunch, I was actually craving cookies. What the hell!?

About 5 hours later, I tested my pee for ketones. Negative.

I was curious: if the product claims that you don’t have to change your diet in order for it to work, but by a matter of hours later the ketones are gone from your body, and you’re not taking packets of this stuff all day and all night, then how does it work, exactly? Isn’t the main idea that it puts you into ketosis all day so you burn fat without the work of a ketogenic diet? 

The Pruvit Ambassador I spoke to told me in response to this question that I’d have to take 2-3 packets a day if this is the case. That sounds really expensive, really gross, and how would that work exactly? 3 packets x 4 hours = 12 hours. So the remaining 12 hours I wouldn’t be in ‘ketosis’? And if I took 3 packets a day, theoretically that would be 330 extra calories. 

Day 2

This day, I drank the caffeinated chocolate flavor. Again cloyingly sweet and bitter, I gulped it down faster than the day before. One things about exogenous ketones that I think everyone can agree with: they taste vile. Like, really BAD. I literally gagged on the last gulp of them and wondered how I was going to do this every day for the foreseeable future. CRAP.

An hour later, my urine had ‘moderate’ ketones in it, and I was starving, but otherwise I felt completely normal, aside from the fact that my stomach was weirdly bloated like a balloon. Funny enough, I didn’t even feel like I’d consumed any caffeine. The Ambassador did say that the caffeine in the product isn’t for energy, it’s to expedite the body’s reaction to the ketones.

I continued to be starving, even though I had not changed my diet (I’m the sort of person who eats similar food every day). I mean, I was so #[email protected]%@ hungry, I hadn’t worked out in days, so this was not the result of being more active or eating less. I was way hungrier than normal.

Days 3-7

Same same. Basically, I felt completely normal, was somewhat bloated, and by 3-4 hours after consumption, my urine showed only trace ketones. I was starving throughout the day, too: I felt like I was on a weight-gain track, not weight loss. After 7 days, I had swallowed about as many packets of Keto/OS that I could possibly stomach.

The results: 

I really didn’t feel any different on Keto/OS than I do in my normal life, and that’s the truth. I had none of the typical issues that people in ketosis suffer from: no GI distress, no ‘keto-flu’ or exhaustion, no appetite suppression, etc.

Maybe I’m used to feeling a certain way because on a lot of days, I eat less than my fair share of carbs? But the hunger. The hunger was real.

I asked my expert why I was so hungry. This is what he had to say:

Low carb diets are all about reducing insulin levels which increases fat mobilization from our adipose tissue and ultimately leads to ketone production from the liver. It is now clear that high levels of exogenous ketones increase insulin levels which shut down fat mobilization. Just another example of “more is not better”. This is probably also why you are feeling hungry…insulin goes up, energy substrates in the blood go down…hunger ensues.

So essentially, I wasn’t burning fat at all. I was just increasing my insulin levels and making myself even hungrier, even though Pruvit claims that Keto/OS increases insulin sensitivity.

I had thought that the longer I was on this supplement, the better it would work. But clearly, it appears to have left my system so quickly that it was never going to build up to a therapeutic level (if there is one).

In short:

  • While exogenous ketones may work for you in terms of appetite suppression, they made me ravenous. This may have been because my insulin levels rose in response to the ketones.
  • I experienced none of the benefits that Pruvit claims it offers. I basically felt normal the entire time I was taking it.
  • I was ketone-free, at least according to my urine, within 3-4 hours of taking Keto/OS. Unless you’re planning on drinking the supplement every 4 hours, I would say that you’re probably not going to sustain ketosis – if you are even in ketosis, that’s another thing – throughout the day and night
  • Exogenous ketones aren’t the same as the ones your body produces. And this means that they probably don’t work the same way, either. For weight loss I would say they’re probably not efficacious. That being said, everyone defines ‘success’ differently, so it would depend on what you’re looking for. This was only my experience. Keto/OS tastes like death, and is extremely expensive. If you want to try it, I’d say try to secure a few packets first before you go all-in.
  • Pruvit states that Keto/OS is safe to give to children. If you’re putting your child on a diet of any sort, it should be supervised, not done by scaling down your dose of exogenous ketones. And don’t put your kid on a diet, okay? Not for weight loss, anyway.

Last but not least: Stop trying to find short cuts in life and especially in weightloss

Instead, let me help you come up with a customized mealplan that fits your goals and lifestyle

Conclusion for fat loss

Based on the evidence I have, there’s little reason to think that exogenous ketones help burn fat or speed up weight loss. In general, these claims are not supported by the current scientific evidence in humans. I have helped many clients achieve nutritional ketosis without the use of ketone supplements. Read Kimberleys’ Keto success story. And if you have any questions about the keto diet feel free to contact me.