Human's ability to produce and oxidize ketone bodies arguably evolved to enhance survival during starvation by providing an energy source for the brain and slowing the breakdown of carbohydrate and protein stores (Owen et al., 1967; Sato et al., 1995; Marshall, 2010). The brain is normally reliant on carbohydrate as a substrate, being less able to metabolize lipids, despite adipose tissue representing a far larger energy store than muscle and liver glycogen. Therefore, during starvation, lipids are used for hepatic ketogenesis and, via ketone bodies, lipids sustain the brain. Endogenous production of the ketone bodies, d-β-hydroxybutyrate (βHB) and acetoacetate (AcAc), increases slowly, driven by interactions between macronutrient availability (i.e., low glucose and high free fatty acids) and hormonal signaling (i.e., low insulin, high glucagon and cortisol). Produced continuously under physiological conditions, blood ketone concentrations increase during starvation (Cahill, 1970), when consuming a “ketogenic” (low carbohydrate, high-fat) diet (Gilbert et al., 2000) or following prolonged exercise (Koeslag et al., 1980).
I (Kim) researched the topic and planned and ran the experiment under the guidance and supervision of Dr. Andreas Eenfeldt, who touched base with me every step of the way to check the experiment design and execution for scientific rigor (to the greatest degree possible) and who has edited this writeup for quality and trustworthiness reasons. I also consulted with other keto experts and researchers to gather feedback both on the experiment design and the results data. They are referenced in the text when this was the case.
It was explained to me that exogenous ketones inhibit lipolysis (breaking down of fat cells), therefore triglycerides should be expected to go down. They theorize that ketones may promote transfer of triglycerides from blood into cells, which primes the pump for fat burning, but to verify would require conducting biopsies to measure blood versus tissue.
It was like getting the benefits of a five-day fast in just 15 minutes! As my body and brain began sucking up the ketones, I felt a rush of energy and my mind became very sharp and focused in ways beyond what I attain doing an extended fast. But in this case it was the 40g of ketones I had just consumed. Even at the two-hour mark, when I took my last reading, I was still in deep ketosis.
Intermittent fasting involves merely changing your eating cycle whereby you prolong the period in which you will have your first meal. This diet plan helps to create a smaller eating window. In doing so, it means that you will consume less amount of calories. In addition to depriving the body some calories, intermittent fasting forces the body to begin burning fats. It does so to compensate for the current deficiency.

Two ground-breaking studies have recently been published on the effects of intermittent fasting on males. One group of researchers studied the effects that 16 hours of intermittent fasting had on males that lift weights. They found that muscle mass stayed the same, fat mass decreased significantly, and the males who fasted for 16 hours a day burned more fat for fuel compared to the control group that only fasted for 12 hours.

Anti-cancer potential: Recent research suggests that ketogenic diets can blunt malignant tumor growth.[5] This is due to the fact cancer cells can’t metabolize ketones effectively to nourish their growth and replication. Astonishingly, one study found that supplementing with BHB salts increases odds of survival in mice with systemic cancer by up to 70% in comparison to mice who didn’t receive exogenous ketones.[6]

Let’s briefly discuss some organic chemistry. Two molecules that are “the same” but mirror images of each other (like your hands) are known as enantiomers, a type of spatial isomer. Beta hydroxybutyrate comes in two forms, D-β-hydroxybutyrate (“right-handed”) and L-β-hydroxybutyrate (“left-handed”). D-β-hydroxybutyrate is the form that is naturally produced in the body and is most bioavailable when taken exogenously.

The current USDA recommendations reflect “unachievable goals” that do not match what research suggests our normal physiological ranges might be[10]. There is not enough evidence to show that sodium restriction is associated with less mortality or cardiovascular morbidity in healthy individuals or individuals with high blood pressure, and there is evidence that sodium restriction might actually be harmful to individuals with heart failure[11]. For serious athletes, and individuals who are active daily, the current recommendations might not only be unwise but unsafe. If you are eating a carbohydrate-restricted diet, this applies to you even more. Don’t stress about the high amounts of sodium in a lot of these ketone supplements, being that they allow for a fast delivery of ketones to the body, which has unique benefits that will be discussed in a separate article.  Instead, change out the frozen dinner and experiment with an effective dose of exogenous ketones.
Exogenous ketones (also known as ketone supplements) and well-formulated ketogenic diets share at least one thing in common. They both result in increased circulating concentrations of beta-hydroxybutyrate (BOHB), but ultimately are associated with very different patterns of ketosis, as well as differing metabolic and physiologic outcomes. In short, they should not be assumed to have equivalent effects simply because they achieve similar BOHB blood levels. Having said that, there are many reasons we should continue to study the various forms and potential applications of ketone supplements.
The two compounds commonly referred to as ‘ketone bodies’ (BOHB and AcAc) are produced and used for multiple purposes across nature from algae to mammals, but seldom in concentrations useful for extraction as human food. For this reason, the source of most exogenous ketones is chemical synthesis. Furthermore, most current research and use of ketone supplements focuses on BOHB. That is because AcAc is chemically unstable – it slowly breaks down to form acetone by releasing of one molecule of CO2.
Most supplements rely on BHB as the source of their exogenous ketone bodies. BHB is converted to acetoacetic acid with a small quantity converted to acetone through a acetoacetate decarboxylase waste pathway. Some of the acetoacetic acid will enter the energy pathway using beta-ketothialase, which converts acetoacetic acid to two Acetyl-CoA molecules (see diagram below2).
The current recommendation for magnesium is 310-320 mg for adult women and 400-420 mg for adult men. Magnesium deficiencies are common; 2005-2006 data indicates that the majority of Americans’ dietary magnesium intake was less than the Estimated Average Requirement (EAR) for the respective age groups[25]. The EAR for a nutrient is about 20% LESS than the RDA. Current data on magnesium intake and deficiency in the US is not readily available, as magnesium testing is not part of routine electrolyte testing in hospitals and clinics[26].
In a nutshell… WOW! The chart above shows each of the games/categories I played, showing my prior 5-day averages compared to the day I took the ketone esters. Compared to my baselines, my scores increased across the board, with the biggest improvements in spatial orientation (+32.2%), working memory (+23.7%), quantitative reasoning (21.5%), task switching (+14.9%), and information processing (+14.9%). Below are more detailed comparisons:
And zero-carb, followed by fasting for two meals, and then followed up by a second zero-carb meal is almost always all you need to get into ketosis fast. By Sunday or Monday morning, after a second night of no carbs, you'll be in a deep enough ketosis that hunger will crash and your energy will surge to help you transition into your low-carb diet of choice.

That’s not to say that the supplements don’t work. They very well might. But they could also be useless—or even dangerous, says Christine Palumbo, RDN, Nominating Committee member for the Academy of Nutrition and Dietetics. As of right now, there’s no way to know. “Currently, there’s just not enough evidence from research studies to answer those questions,” Barnes adds.
There have been studies done on long term ketogenic diets. This 2004 paper inn Experimental & Clinical Cardiology titled ‘Long-term effects of a ketogenic diet in obese patients’ concluded that obese patients following a ketogenic diet for 24 ‘reduced the body weight and body mass index of the patients. Furthermore, it decreased the level of triglycerides, LDL cholesterol and blood glucose, and increased the level of HDL cholesterol. Administering a ketogenic diet for a relatively longer period of time did not produce any significant side effects in the patients. Therefore, the present study confirms that it is safe to use a ketogenic diet for a longer period of time than previously demonstrated.’
To be in ketosis, you need to get very specific about the macronutrient ratios hanging off your fork. This means eating 75% fats, 20% protein and 5% carbohydrates. It’ll see you getting 5-10% of your total calories from carbohydrates, which is roughly 25-30g of carbs per day, and diligently keeping this below the 50g threshold creates the ketosis that burns stored fat. Unlike the no-limit-protein option on the table when going low carb, eating more than 0.67-0.81g of protein per pound of bodyweight can hoof you out of ketosis because too much of it can be converted into glucose, blunting the benefits of the ketones. On the plus side, you will have a high fat intake, making your energy levels more balanced so you can train at higher intensities.
The protocols carried out in these studies were approved by the the South West Frenchay NHS REC (15/SW/0244) (Study 1) and London Queen's Square REC (14/LO/0288) (Study 2 and 3). The studies were carried out in accordance with the recommendations of the Declaration of Helsinki, apart from pre-registration in a database. All subjects gave written informed consent in accordance with the Declaration of Helsinki.
Elliot received his BS in Biochemistry from the University of Minnesota and has been a freelance writer specializing in nutritional and health sciences for the past 5 years. He is thoroughly passionate about exercise, nutrition, and dietary supplementation, especially how they play a role in human health, longevity, and performance. In his free time you can most likely find him lifting weights at the gym or out hiking through the mountains of Colorado. He will also host the upcoming BioKeto podcast. You can connect with him on Facebook ( and Instagram (@eazy_ell)
Another effect of the ketone drinks was to lower blood glucose, free fatty acids, and triglyceride levels. This sounds great. Elevated levels of all those markers are harbingers of disease, particularly if they remain chronically elevated. But think about what this means. If free fatty acids go down, that means adipose tissue isn’t being liberated for burning.
Also, this experiement should be of interest. Two men followed a ‘traditional Eskimo’ diet for 1 year. After the year eating a low carb high fat diet, it was found that the men had a diminished tolerance to carbohydrates, something that did not occur in Eskimos eating the same diet. It took the mean nearly a month of eating a ‘normal diet’ before their glucose tolerance returned to baseline. 
If the goal is to deplete glucose levels so that we can start producing ketone bodies, then forcibly exerting physical energy through exercise is a great way to go about it. Keeping it relatively low intensity to begin with and working out in the morning is recommended as this helps to keep down your cortisol (stress hormone) levels. This only applies at the beginning of your keto adaptation process, as intense workouts such as HIIT once already keto-adapted will be completely fine.

Exogenous ketones don’t seem to improve high-intensity, glucose-intensive exercise, increasing fat burning during steady state exercise but dropping top-end high-intensity performance. Another study found that ketone dieters reduced 50-minute time trial performance in cyclists, though another group of researchers have criticized the methods. Even when a ketone ester didn’t improve performance in the shuttle run to exhaustion and 15 meter sprint repeats, it did reduce the drop in brain function following the exercise.
The liver is always producing ketones to some small degree and they are always present in the bloodstream. Under normal dietary conditions, ketone concentrations are simply too low to be of any significant benefit. A ketogenic diet and exogenous ketone supplements will increase the amount of ketone in your body. The idea that  ketones are “toxic” is ridiculous. Ketones are a normal physiological substance that play many important roles in the human body.

I carried out a survey among Diet Doctor users as background research to the experiment (a big thank you to the 638 people who responded!). In the survey, 28% of the respondents reported that they do take ketone supplements. The top four benefits that these respondents reported experiencing were increased energy, improved focus/cognition, reduced hunger and weight loss.

Exogenous ketones have a wide range of benefits that can enhance your fat-burning lifestyle. I personally use them daily as a strategy to heighten my mental performance and give my workouts an extra boost. For these purposes, I have also found it logical to combine exogenous ketones with other known health and performance boosting agents such as branched-chain amino acids and medicinal mushrooms.
A small side effect for some people is “ketosis breath”. Many people on a ketogenic diet have experienced this temporary phenomenon, and those taking exogenous ketones can experience it as well. The smell of your breath when you are early in the ketogenic diet can have a hint of acetone to it, and it might be mildly unpleasant, but it’s also harmless. Most gum is pretty low in carbohydrates and is a great option while your keto breath fades.
I also chatted to some Prüvit reps, who told me that it might be necessary to keep taking the supplements for a couple of months to start to see more elevated ketones. Well, the proof is in the pudding (or in this case, in the fluorescent-coloured, artificial-tasting pink drink). But I would hesitate before spending money on a two-month supply just to find out if that’s true. Real Ketones’ Kegenix Prime was associated with a decrease blood ketones. Not a good start, and we’ll get back to this point later.
We will go deep in the science behind this fascinating diet and then review some of the best exogenous ketone supplements out there in the market. Because without the knowledge and the right information about exogenous ketones that you can properly follow, you might never reach your goals and you may as well keep eating that mashed potato for dinner and club sandwich for lunch.

Also, this experiement should be of interest. Two men followed a ‘traditional Eskimo’ diet for 1 year. After the year eating a low carb high fat diet, it was found that the men had a diminished tolerance to carbohydrates, something that did not occur in Eskimos eating the same diet. It took the mean nearly a month of eating a ‘normal diet’ before their glucose tolerance returned to baseline. 

BHB Salts and exogenous ketone supplements are literally changing the supplement industry. These products are pretty new and a little more expensive than other supplements. But I’d rather pay for something that works then spend tons of money chasing products that claim to work. One of the most popular ketone supplements is Ketōnd. You can check out our review here.

In terms of getting back into Ketosis, Keto//OS would most likely be a better choice (and a change back to a low-carb diet, of course) because it not only has MCTs, but also provides beta-hydroxybutyrate, which is the product that comes from your liver after it synthesizes acetoacetate. However, since this product also has caffeine (great for workouts), you might want to go with the decaf if you’re strictly looking for a ketosis jumpstart.
Second, take a look back at table 2. Kegenix Prime scored as the “winning brand” for 4 out of the 7 markers tested: mental performance, satiety, mental clarity and energy. Compared to the other supplements, it also scored highest for physical performance, although none of the supplements were listed as a “winner” since the placebo outperformed them all for that marker.
Too much cortisol tells the liver that you are in physical danger and need a lot of energy fast. The brain doesn't understand the difference between physical danger and emotional stress. When emotionally stressed, the brain thinks you're in a life-and-death situation, so the liver comes to your rescue and gives you the glucose you need to fight off your attacker.

I stumbled onto this trend before it even blew up, I have read just about every peer-review journal of the topic, I have trialed as well as tested different methods and keto products (exogenous ketones, MCT oils, pills, etc), and lastly, I have reported and analyzed my performance to share with you all. It hasn't been an easy task, but I have also seen the fruits of the labor, and the fruit is sweet.
The “BHB salt” is simply a compound that consists of sodium (Na+), potassium (K+), and the ketone body β-hydroxybutyrate. In supplements like Pruvit’s Keto OS these individual components are being held together by ionic bonds; however, when you consume the product, it is absorbed into the blood where it dissociates into free Na+, K+, and BHB since it is a water-based solution. Thus, consuming the product directly and immediately puts more ketones into your blood.
The concentrations of blood d-βHB after KE drinks were highly repeatable whether consumed whilst fasted or fed (Figures 4F,G). The d-βHB Cmax values ranged from 1.3 to 3.5 mM when fed and 2.3 to 4.7 mM when fasted. There was no significant effect of visit order on d-βHB kinetics, with the maximal difference in d-βHB Cmax reached by one individual being 1.2 mM when fed and 1.9 mM when fasted. Approximately 61% of the variation in the data was attributable to feeding (fed vs. fasted), <1% to visit order, 16% to inter-participant variability, and the residual 24% variability due to non-specific random effects.
Great question. So if you are already in nutritional ketosis from your diet, exogenous ketones would still help raise ketone (energy) levels when you want that (maybe for focus at work or energy at the gym. They also help get you back into ketosis after cheat meals and skip the “keto flu” which is the period when your body is using up stored glycogen.

Studies show that exercising depletes both liver and muscle glycogen faster than fasting [4]. For example, swimming for an hour and a half depletes the same amount of glycogen as a 24-hour fast. However, it's a good idea to eat a tiny amount of carbs and protein before and after a workout to prevent muscle damage. Your body can break down proteins in your muscles if glycogen stores get depleted during workouts.

I wrote this post at about the same time Germany won the World Cup in Rio de Janeiro in 2014. There’s been a lot of moving and shaking in the world of exogenous ketones since then, not to mention soccer. Looking back on my post, I still consider it relevant in terms of what exogenous ketones possibly can (and cannot) do for performance. In this case, to see if exogenous ketone esters provide me a “boost” by allowing me to do the same amount of work while expending less energy (and work at a relatively lower VO2) compared to no supplementation.

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