For the past few million years, the only way for humans to make use of ketones for fuel was to restrict carbohydrates low enough and long enough to induce the liver to make them. This is admittedly hard for many people to do in a world that still believes that dietary carbs are good and fats are bad. An emerging alternative is to consume ketones as a dietary supplement. The research into how these function in the body and what benefits they can confer remains early stage, but there are already a number of such products available for sale. In this section, we will discuss how exogenous ketones affect blood ketone levels, and how they may influence health and disease compared to ketones produced within the body.
Personally, I do this on Friday night to Saturday night, so if something happens and my hunger hasn’t crashed by Sunday morning, I have another day that I can go zero carb to keep the momentum going. While the body will trigger ketosis as soon as you run out of glycogen, hunger is attached to your triglyceride and insulin levels, which might take an extra day to normalize.
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.
Good question. There have been many tests and studies that have been conducted to see if ketogenic supplements genuinely do work and many of these studies have shown that ketosis theories are correct. Adding ketones to your body and using fats as a resource of energy has some fantastic effects and if done right can help your body fight all sorts of ailments such as cancer, heart disease, diabetes and many other illnesses that can only be cured by chemical therapy. Keto therapy or nutritional ketosis is paving the way for more natural solutions, and it's a good thing that scientists have created these exogenous ketone supplements that help us induce more ketones in our body.
Firstly, in a randomized four-arm cross-over study, blood βHB concentrations were compared following ingestion of equal amounts of βHB as a KE or a KS at two doses by healthy volunteers at rest (Study 1; n = 15). Secondly, in a randomized five-arm cross-over study, inter- and intra-participant repeatability of ketosis was examined following ingestion of identical KE drinks, twice whilst fed and twice whilst fasted. As a control, participants also consumed one isocaloric (1.9−1) dextrose drink (Study 2; n = 16). Finally, blood d-βHB was measured after equal amounts of KE were given as three drinks (n = 12) or a constant nasogastric (NG) infusion (n = 4) (Study 3; total n = 14) over 9 h.
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.

Unless otherwise stated, statistical analysis was conducted using Prism 6™ software. Values, expressed as means ± SEM, were considered significantly different at p < 0.05. Initial tests were undertaken to ensure that normality and sphericity assumptions were not violated. Subsequently, either one or two way repeated measures ANOVA, or Freidman's test with post-hoc Tukey or Dunnet's correction were performed, to compare changing concentrations of substrates, electrolytes, pH, insulin, breath and urinary βHB: both over time and between study interventions. In Study 2, data from each of the two study visits in each condition (fed and fasted) completed by an individual were included in the analysis.
Beta-Hydroxybutyrate (BHB) is naturally ketone body that is produced when free fatty acids are broken down in the liver. The other two types of Ketone bodies are acetoacetate (AcAc) and acetone. Ketones provide pure energy to fuel the human brain and other tissues. The elevation in ketones in your blood have been a rapidly emerging area of research and studies are continuing to show improvements in performance, brown adipose tissue, and several other possible applications.

Obviously, cutting carbs is much easier than not eating anything at all for days on end. It's also safer for people with diabetes as it leads to a gradual decline in blood glucose [2]. The carbs you have to reduce are known as net carbs. Those are the carbs that your body uses to make glucose. You calculate them by subtracting the grams of fiber from total carbs in a food item.
Since beta hydroxybutyrate is transported throughout the body via the blood, the best way to check your true BHB levels is through a blood test. The good news is that you can just use a simple finger prick and an at home method that is very similar to how diabetics check their glucose. The bad news is that it can be pretty expensive. Each strip and time you test can be around $4-6.
At baseline, 4 h after intragastric gavage, the elevation of blood ketones was inversely related to the reduction of blood glucose compared to controls following the administration of MCT (5 g/kg) (p = 0.008) and BMS + MCT (5 g/kg) (p = 0.039) . There was no significant correlation between blood ketone levels and blood glucose levels compared to controls for any other ketone supplemented group at baseline (Fig. 4a). At week 4, 4 h after intragastric gavage, there was a significant correlation between blood ketone levels and blood glucose levels compared to controls in MCT (10 g/kg) and BMS + MCT (10 g/kg) (p < 0.0001, p < 0.0001) (Fig. 4b).
KE was synthesized as previously described [29]. BMS is a novel agent (sodium/potassium- βHB mineral salt) supplied as a 50 % solution containing approximately 375 mg/g of pure βHB and 125 mg/g of sodium/potassium. Both KE and BMS were developed and synthesized in collaboration with Savind Inc. Pharmaceutical grade MCT oil (~65 % caprylic triglyceride; 45 % capric triglyceride) was purchased from Now Foods (Bloomingdale, IL). BMS was formulated in a 1:1 ratio with MCT at the University of South Florida (USF), yielding a final mixture of 25 % water, 25 % pure βHB mineral salt and 50 % MCT. BD was purchased from Sigma-Aldrich (Prod # B84785, Milwaukee, WI).
But going keto takes work. You have to overhaul your diet, restrict certain classes of foods, and pay close attention to what you eat. People prefer to avoid work if they can. They like shortcuts. Exogenous ketone supplements promise a shortcut—swallow this pill or mix this powder into your water and see your ketones skyrocket without changing the rest of your diet.

Keep these studies in mind as your body tries to play tricks on you during your first day of fasting.  Even after three days of fasting, health complications are highly unlikely. However, it is important to know about the possible issues that can be caused by fasting. If you choose to incorporate fasting into your daily diet, you typically want to eat every day as well. Occasionally going on a longer period of fasting.
Athletic performance benefits: The use of exogenous ketone supplements for bettering physical/athletic performance is promising for several reasons. Firstly, taking exogenous ketones (particularly BHB salts) induces acute nutritional ketosis for upwards of eight hours, mimicking fasting physiology (e.g. increases fat burning, insulin sensitivity, etc.).[3]
Response inhibition is the ability to suppress inappropriate responses that interfere with goal-directed actions. Two cards are shown, one above the other, each containing the name of a color in a certain color. The goal is to rapidly indicate if the meaning of the color on top (i.e. “yellow”) matches the color of the color on the bottom (i.e., card says “red” but is colored yellow).
Full disclosure: after carrying out the background research, I was already, as you might imagine, feeling a little less neutral about these products. You may have noticed a hint of that in part 1 of the 2-part video series we made about the project (watch part 2 at the top of this page!). However, and although this was by no means a controlled scientific study under laboratory conditions, we designed the experiment in a very objective way. The aim was to give the supplements the best possible chance of showing the benefits they are claimed to have.
Beta-Hydroxybutyrate (BHB) is naturally ketone body that is produced when free fatty acids are broken down in the liver. The other two types of Ketone bodies are acetoacetate (AcAc) and acetone. Ketones provide pure energy to fuel the human brain and other tissues. The elevation in ketones in your blood have been a rapidly emerging area of research and studies are continuing to show improvements in performance, brown adipose tissue, and several other possible applications.
International Patent # PCT/US2014/031237, University of South Florida, D.P. D’Agostino, S. Kesl, P. Arnold, “Compositions and Methods for Producing Elevated and Sustained Ketosis”. P. Arnold (Savind) has received financial support (ONR N000140610105 and N000140910244) from D.P. D’Agostino (USF) to synthesize ketone esters. The remaining authors have no conflicts of interest.
Neuroprotective benefits: A natural part of the aging process is neurodegeneration, which is largely responsible for cognitive defects like Alzheimer’s disease. Recent research suggests that exogenous ketone supplementation can drastically slow neurodegeneration and the resulting decrease in mental function.[7] However, the mechanism behind this finding remains to be elucidated; though, researchers suggest exogenous ketones act to reduce brain inflammation. Glucose, on the contrary, may actually accelerate inflammatory response in the brain.[8]
Ketogenesis is the metabolism of fatty acids by β-oxidation. 4 This process gives acetyl CoA which then leads to β-hydroxy-β-methyglutaryl-CoA (HMG-CoA) as seen below5. HMG-CoA converts into Acetoacetone which can switch back and forth to BHB. Acetoacetone to Acetone conversion is irreversible (on the left below). Acetoacetate and BHB (via acetoacetate) are used to produce energy when converted back into acetyl-CoA within a cell’s mitochondria whilst Acetone is excreted in the breath and urine.4
Task switching is the process of adapting to changing circumstances (switching from one goal to another). Two cards are shown one above the other, and a combination of letter and a number (i.e., “A4”) will appear on one of the two cards. If it appears on top, the task is to indicate whether the number is an even number, and if on the bottom the task is to indicate whether the letter is a vowel.
EK use can be compared to the nootropics that have been developed for optimizing focus, memory creation, and faster cognitive performance. While you may not notice this effect on a minute to minute basis if you keep a journal of “forgetful moments” you’ll find that you have fewer of them as time goes on. You’ll also find that you’re able to come up with better ideas, and your workflow is more efficient through the day (10, 11).
Another important difference between endogenous and exogenous BOHB is that most synthetic BOHB used in dietary supplements is a mixture of the two ‘D’ and ‘L’ isomers, whereas endogenously produced BOHB consists of just the D-isomer. Metabolically, the two isomers are very different, and current published information indicates that most of the energy and signaling benefits of BOHB derive from the D-form. This is potentially problematic because the L-isomers are not metabolized via the same chemical pathways as the D-forms (Lincoln 1987, Stubbs 2017), and it remains unclear whether humans can convert the L-form to the D-form.
It’s not clear that the Weir coefficients used to estimate EE are relevant for someone in ketosis, let alone someone ingesting exogenous BHB. (The Weir formula states that EE is approximated by 3.94 * VO2 + 1.11 * VCO2, where VO2 and VCO2 are measured in L/min; 3.94 and 1.11 are the Weir coefficients, and they are derived by tabulating the stoichiometry of lipid synthesis and oxidation of fat and glucose and calculating the amount of oxygen consumed and carbon dioxide generated.) While this doesn’t impact the main observation—less oxygen was consumed with higher ketones—it does impact the estimation of EE and substrate use.

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Medical Disclaimer: The material on this site is provided for informational purposes only and is not medical advice. Always consult your physician before beginning any diet or exercise program.

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