Even though endurance athletes can train in a carb depleted state, they will generally consume carbohydrates in the lead up to a race (the athlete is seeking to increase the ability to run off fats by training in a carb depleted state, then benefiting from both fats AND carbs come race day). Likewise, with the brain, even though the brain can function off ketones, does it mean it’s the best state for brain function?
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

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.


This was a big surprise. We were at the very least expecting that drinking a ketone supplement would cause blood ketones to rise, but an average increase of 0.33 mmol/L is very small. The supplement associated with the highest average increase in blood ketones was Prüvit’s Keto-OS Max, but it was only an increase of 0.6 mmol/L. Brianna Stubbs, the ketone researcher I consulted with, agrees that an increase of below 2.0-3.0 mmol/L is unlikely to be of much use.
Hello! I’m planning on taking a short vacation and will be having “kept friendly” drinks, mostly vodka and water with lemon and stevia. When should I take my exogenous ketones? That night before bed or early the next morning or after the 3 day vacation is completely over? I’m unsure how to manage this to have the best odds of staying in ketosis and get back to burning FAT. Also, I just purchased Instaketones from Julian Bakery, what are your thoughts on this brand? Thanks for what you do!
The main distraction which we have these days in our lives are the gadgets. Therefore, in order to fall asleep early, you need to make sure that you turn off your phones, tablets, computer, TV etc… at least 30 minutes before bedtime. This helps avoid insomnia as well as keep you away from the bright blue light which can interfere with your biorhythm.
Another factor to consider is that in nutritional ketosis the liver makes a steady supply of ketones and continuously releases them into the circulation. In contrast, most ketone supplement protocols involve bolus intakes that don’t mimic the endogenous release pattern. The extent to which this impacts metabolic and signaling responses across different tissues remains unclear.
Why is this desirable? Think about energy production in your body much like macro energy consumption on a planetary level. Coal is gross and dirty and messes tons of different things up. You need to continue to burn it to get energy. Solar power is free, clean and pretty much limitless. This is pretty much the same story when you are burning carbs (coal) versus fats (solar) for energy.

Importantly, at Diet Doctor we do not think you need to spend any extra money at all in order to revolutionize your health. You can achieve radiant health just by enjoying authentic food that is naturally low in carbohydrates, getting plenty of sleep and some exercise (going for a walk is free) and reducing stress. A lot of you who answered the survey made exactly these points in your explanations of reasons for not taking the supplements. I whole-heartedly agree.
In fact this was one of the biggest surprises I had when exploring ketosis. For years I have been following a cyclical lower carb diet. For years I wouldn’t consume a carb until later in the afternoon (ala Carb Backloading style). After eating 5 days without any carbs I tested my ketone levels… they were 0.1 mmol. This reading was done first thing in the morning (10 hours fasted) after 5 days without a carb in my diet.
Hi Mark, sorry this is off topic but not sure where to send a question for a future Ask Mark. I’m about to go into my yearly physical and I am wondering if there is any specific bloodwork that you like to do for your annual check up. I’m 47 year’s old and the than the basic blood work like lipid panel, etc..I’m going to ask my doctor to test my testosterone, HbA1C, fasting insulin, and Vitamin D levels. I’m also going to ask my doctor to do a stool test to check for parasites or other infections I may have picked up from open water swimming for triathlons. Can you recommend any other blood work that might be useful? Thanks!

Neuroprotection: As humans age, the brain becomes more susceptible to neurodegeneration and subsequent conditions such as Alzheimer’s and Parkinson’s disease. Exogenous ketone supplementation appears to ameliorate the typical decline in cognitive function that comes with aging. The likely mechanism for this neuroprotective property is that ketone bodies reduce the inflammation and hyperexcitability that is normally exhibited as glucose metabolism declines in the brain.18, 19
Calories do matter, even on a ketogenic diet. If you consume more calories than your body uses, you’re going to gain weight. Period. What you mean to say is that it’s very difficult to eat your entire day’s worth of calories on a ketogenic diet because fats are so satiating. This distinction is important to keep in mind for those who generally have a voracious appetite (like me).

Exogenous ketones are also for those just looking to try it out. It lets anyone be able to access ketones simply by consuming these exogenous forms of ketones. Technically, MCTs are not an exogenous ketone such as BHB salts. They’re not ketones. But they readily convert into ketones. So MCT oils and powders are a great source of endogenous ketones. The end result is similar, and thus this top 5 list includes MCT oil powders as well as BHB salts.
The Zenwise Keto Life BHB Salt uses a custom calcium, magnesium and sodium ketone complex to help access ketones for fuel without the low carb diet or fasting. This product is another all-natural option that goes as far as using turmeric for its added coloring. It is a proven product with hundreds of happy customers. They seem to have a strong grasp on the lemonade side of the exogenous market with their Raspberry Lemonade and Wild Limeade flavor choices.
You are probably wondering how there could possibly be a benefit to eating less frequently that goes beyond what you are already getting with a ketogenic diet. Restricting carbs and eating enough fat and protein does come with a plethora of health benefits, but when you add intermittent fasting to your lifestyle you can increase energy and reverse aging by harnessing the power of a nobel prize winning process.
Safety Warning — KEEP OUT OF REACH OF CHILDERN. This product is only intended to be consumed by healthy adults 18 years of age or older. Do not use if you are pregnant, trying to become pregnant, breast feeding, have known medical conditions (including but not limited to diabetes, kidney, heart, or liver disease) or are taking prescription or OTC medication(s). Consult with your health care practitioner before using this product These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. —
The effects of ketone drinks on endogenous insulin secretion are unclear. Whilst the small increase in plasma insulin after KE and KS drinks may have been due to the small quantity of dextrose in the diluent, it has been proposed that ketones could potentiate or even stimulate insulin secretion. Isolated pancreatic islets secreted insulin when stimulated by ketones at glucose concentrations of >5 mM (Biden and Taylor, 1983), and small amounts of insulin are secreted in vivo following exposure to exogenous ketones in animals (Madison et al., 1964; Miles et al., 1981). In response to an intra-venous 10 mM glucose clamp, ketone ester drinks increased glucose uptake and plasma insulin (Holdsworth et al., 2017). The increases in insulin with ketone drinks taken whilst fasted were small compared to the increases seen when the ketone ester drink was consumed with a meal and with consumption of a dextrose drink. Furthermore, the lack of difference in peak plasma insulin between the two latter conditions indicates that nutritional ketosis did not inhibit or increase normal carbohydrate induced insulin production.

One other thing I must point out is also that we are talking about being in ketosis and not being fully keto adapted. You enter ketosis when your body starts producing ketones above a specified level, being fully keto adapted means that your body is full adapted to  use fat as your primary energy source and that the production of certain enzymes in your body is fully adapted. This doesn’t happen in one day and it takes about 1 month on average to be fully keto adapted. But we are not looking for this as we just want to end the most unpleasant period and to start losing weight.

In fact this was one of the biggest surprises I had when exploring ketosis. For years I have been following a cyclical lower carb diet. For years I wouldn’t consume a carb until later in the afternoon (ala Carb Backloading style). After eating 5 days without any carbs I tested my ketone levels… they were 0.1 mmol. This reading was done first thing in the morning (10 hours fasted) after 5 days without a carb in my diet.
Should We Use Exogenous Ketones? Ketosis serves a purpose, and it’s probably why we’re able to survive on this planet. Being able to go without eating and use stored fats for energy is a survival tool and possibly far more as we’re now seeing with the keto diet. But it’s probably not a good idea to constantly take exogenous ketones and eat a high carb diet (high blood glucose levels). It’s not natural for the body to have high blood glucose and use ketones. This is a personal opinion, so 

2. Shimazu, T., Hirschey, M.D., Newman, J., He, W., Shirakawa, K., Le Moan, N., Grueter, C.A., Lim, H., Saunders, L.R., Stevens, R.D., Newgard, C.B., Farese Jr, R.V., De Cabo, R., Ulrich, S., Akassoglou, K., and Verdin, E. (2013). Suppression of oxidative stress by β-hydroxybutyrate, an endogenous histone deacetylase inhibitor. Science 339, 211-214.
Plasma glucose, free fatty acids (FFA), triglycerides (TG) and urinary d-βHB were assayed using a commercial semi-automated bench-top analyzer (ABX Pentra, Montpellier, France), and insulin was measured using a commercially available ELISA assay (Mercodia, Uppsala, Sweden). Both the pure liquid KS and KE, and a subset of plasma (n = 5) and urine (n = 10) samples from a subset of participants in Study 1 underwent analysis using GC-MS and a chiral column, and the concentrations of l-βHB was calculated using the enzymatically determined concentration of d-βHB and the ratio of the d/l-βHB peaks obtained through GC-MS. Acetoacetate was assayed using an enzymatic method (Bergmeyer, 1965), and breath acetone was measured using GC-MS (Study 1) or with a handheld electrochemical device (Study 2; NTT DOCOMO, Japan) (Toyooka et al., 2013).

With single doses of the D-BHB ester as a sports drink, gastrointestinal (GI) side effects are rare. Some studies have reported mild GI side-effects of HVMN Ketone drinks at extremely high doses (4x serving size) or when given in a thick, meal replacement formulation.10,13 However, other studies of athletes reported there were no side-effects of ketone ester drinks hindering sport performance.11,14
Despite the recent growth of the ketone salt market, there is very little published work analyzing the effects of these products on any biomarkers or performance measurements in humans. Several studies have been carried out in rats,6,7 with blood BHB levels being relatively low (<0.5 mM) post-consumption of salt drinks. In humans, ketone salts provided peak D-BHB levels of 1 mM, whereas the same amount of BHB in a ketone ester (BD-BHB) raised blood BHB to 2.8 mM.5
There are three types of ketones produced when you’re on ketogenic diet: acetoacetate, beta-hydroxybutyrate (BHB), and acetone. The kinds that you’ll find in your supplements are BHB because your body can readily use and absorb them. This means that not all ketones are created equal and there are several different types, each with unique properties that are worth considering when shopping.
As ketone drinks can deliver nutritional ketosis without fasting, we investigated the effect of food on KE uptake and metabolism. It is well documented that food in the gut can slow, or prevent, the uptake of small hydrophilic hydrocarbons, such as βHB (Melander, 1978; Toothaker and Welling, 1980; Horowitz et al., 1989; Fraser et al., 1995), so decreased gut βHB uptake is probably the cause of lower blood βHB following the meal. Despite higher blood βHB concentrations in the fasted state, the meal did not alter plasma AcAc. This suggests that the rate of conversion of βHB to AcAc may not match the rate of appearance of βHB following KE consumption. Alternatively, meal-induced changes in the hepatic ratio of NAD+:NADH may have altered the conversion of βHB to AcAc (Himwich et al., 1937; Desrochers et al., 1992).
Keto-adaption is a complex set of metabolic processes in which the body shifts from using primarily glucose for energy to using largely ketones and fat for energy. Achieving ketosis doesn’t mean the body is maximizing the use of these ketones; it takes longer than a few days for the body to get used to burning fat and ketones as its predominant fuels.

Most people confuse thirst for hunger, and it's crucial to not make that mistake when you're dieting. Try to drink water first before heading to the fridge to get some snacks--you might realize that you're not really hungry at all and you are, in fact, only thirsty. Training yourself to spot the difference between hunger and thirst will help you induce ketosis faster. 

Plecko B., Stoeckler-Ipsiroglu S., Schober E., Harrer G., Mlynarik V., Gruber S., et al. . (2002). Oral beta-hydroxybutyrate supplementation in two patients with hyperinsulinemic hypoglycemia: monitoring of beta-hydroxybutyrate levels in blood and cerebrospinal fluid, and in the brain by in vivo magnetic resonance spectroscopy. Pediatr. Res. 52, 301–306. 10.1203/01.PDR.0000019439.27135.2B [PubMed] [CrossRef]
I don’t recommend that you go straight for a 1-2 day fast, but begin by restricting yourself to certain eating windows. Typically people restrict themselves to the hours of 5pm – 11pm. People often refer to their fasting windows by numbers: 19/5 or 21/3, for example, means 19 hours of fasting and 5 hours eating or 21 hours fasting and 3 hours eating, respectively.
If you’re somebody who isn’t already a keto-goer, then you might be wondering why? Why do I need to limit my carbohydrate intake to get my body into a state of ketosis? Simply put, and without getting to technical; you want your body to be in a constant state where fat is the is the primary source of fuel for the body rather than glucose. You see, once you eat carbs, the body will break this down into glucose which it will then use for fuel before tapping into your fat reserves for energy. If you limit the amount of glucose that is in your system by restricting your carbohydrate intake, the body has no choice but to tap into your fat stores for energy. Fats are metabolised in the liver where ketones are then produced for your physical and cognitive needs.
There are three types of ketones produced when you’re on ketogenic diet: acetoacetate, beta-hydroxybutyrate (BHB), and acetone. The kinds that you’ll find in your supplements are BHB because your body can readily use and absorb them. This means that not all ketones are created equal and there are several different types, each with unique properties that are worth considering when shopping.
It's also important to note that you probably should follow a low carb diet or ketosis diet when using this product. Your brain prefers glucose as fuel because it's easier for the body to metabolize from food, so if you are eating a standard American diet of 100g+ carbs per day, or excessive protein, this won't help you lose weight, even with exercise because you'll have more than enough glucose to power your brain. Carbohydrate restriction, moderate protein, and lots of good healthy fat is what puts your body into ketosis.
I started this website because it was hard to find trustworthy, evidence-based information about the ketogenic diet. Information that was published and peer reviewed by respected scientific journals. After years of research, I'm sure you'll achieve great results in a healthy way following my advice. I do my best to translate scientific research jargon into plain English. Remember, it's always a good idea to consult a doctor before starting a new diet!
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 kCal.kg−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.
Effects of ketone supplementation on blood βHB. a, b Blood βHB levels at times 0, 0.5, 1, 4, 8, and 12 h post intragastric gavage for ketone supplements tested. a BMS + MCT and MCT supplementation rapidly elevated and sustained significant βHB elevation compared to controls for the duration of the 4-week dose escalation study. BMS did not significantly elevate βHB at any time point tested compared to controls. b BD and KE supplements, maintained at 5 g/kg, significantly elevated βHB levels for the duration of the 4-week study. Two-Way ANOVA with Tukey’s post hoc test, results considered significant if p < 0.05. Error bars represent mean (SD)

Some common short-term effects that some people experience in the early stages of the process are excessive thirst, fatigue and keto constipation. These minor side-effects occur due to a sudden change to a persons diet, but as I said, once your body starts to adjust to the process, you will start to feel normal again, if not better than before you started. We understand that constipation isn't exactly fun, but it's a small price to pay to experience the long-term health benefits. 

Our bodies are produce three types of ketone bodies for fuel: beta-hydroxybutyrate (BHB), acetoacetate (AcAc), and acetone. Each is used by the body differently. Acetone is the least abundant, produced in much smaller amounts, and is usually exhaled through the lungs rather than being used as fuel.3 Acetoacetate is part of the metabolic pathway whereby humans make and use ketones, but it tends to be found in the blood at lower levels than BHB.


Directions — — As a dietary supplement, mix 1 scoop of ketone powder with 8-12 oz of water To avoid gastrointestinal discomfort, start with 1/2 scoop (or even less) and gradually increase to a full serving. Best consumed prior to exercise to enhance performance. Do not exceed 3 scoops per day. As a dietary supplement take 1 serving of PX Ketotropin twice daily. Ideally the 1st servings (4 capsules) should be taken prior to the first meal of the day. Consume 2nd serving 30 minutes prior to strenuous physical activity. If no physical activity is performed please consumer 2nd serving prior to afternoon meal. Additional servings can be taken in between meals throughout the day if needed. Do not consume more than 6 servings of PX Ketotropin

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