The best time to start a one day fast is in the evening (neither morning nor the night) – preferably, around 6 pm. It won’t make you lose your vital energy during the daytime workouts, nor does it let you sleep with undigested foodstuff in your stomach. Taking late meals and sleeping with undigested food doesn’t allow your body to rest. So the natural healing mechanism of your body fails during the sleep time as the entire resources are busy digesting your food.
How BHB turns into energy is a fairly simple process. As we’ve mentioned, beta hydroxybutryate eventually leads to energy production after you consume it or after your body breaks stored body fat down. It does this by going into the cell, entering the mitochondria (energy factories) at which stage it cleaves the carboxyl acid group and becomes acetoacetate (another “ketone body”). Acetoacetate turns into acetoacetyl-CoA, which then is cleaved to acetone (another “ketone body”) and acetyl-CoA. Acetyl-CoA is the whole reason we want BHB in the first place. This jumps into what is called the Kreb’s cycle (don’t you remember any of your biochemistry classes?) and is churned into ATP — the energy currency of your cells!

Ketone supplements contain exogenous ketones—synthetic ketones made in a lab. Most use a type of ketone called beta-hydroxybutyrate (BHB), which is the same as the ketones the body produces naturally. “We’re literally biohacking," says Amie Heverly, who began taking a ketone supplement called Prüvit last year and now works as a promoter selling Prüvit products. "You’re not adding a foreign substance to your body, because BHB is identical to what your body would naturally produce,” she explains.
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.
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.
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.
Halitosis (bad breath) – If you’re on a ketogenic diet you are probably aware that as the body starts to metabolize fat, ketones can cause poor breath. There is very little one can do about this, it’s just the nature of the beast. Unfortunately, this can also arise when using exogenous ketones, but it’s not as lasting as when on a ketogenic diet. Chewing gum or mints is about the best option if it becomes a noticeable issue. This maybe caused by over consumption of the ketone supplement, tailoring the quantity consumed may prevent excess BHB being converted to acetone, which is likely excreted by the lungs.
The same question posed in a different way can be, what’s better, getting protein from powder or from a grass-fed steak or wild salmon? Omega-3 from supplements or from a variety of healthy wild fish? Just like with health supplements where you consume an isolated nutrient instead of the whole food where it comes from, if it’s possible to get what you need from whole food or nutrition, then that’s probably the best choice.

Blood, urine, plasma, and breath ketone concentrations following mole-matched ketone ester or isocaloric dextrose drinks in fed and fasted subjects (n = 16) at rest. Data from both of the two study visits in each condition (fed and fasted) completed by an individual are included in the analysis. Values are means ± SEM. (A) Blood d-βHB. (B) AUC of blood d-βHB. (C) Urine d-βHB excretion. (D) Plasma acetoacetate (AcAc). (E) Measured breath acetone (ppm = parts per million). (F,G) Mean d-βHB Cmax and difference between βHB Cmax over two visits when subjects separately consumed two ketone ester drinks in both the fed (F) and fasted (G) state. X axis = mean d-βHB Cmax of the 2 visits (mM), Y axis = difference between d-βHB Cmax in each visit. 95% confidence limits are shown as dotted lines. Significance denoted by: *p < 0.05 fed vs. fasted.
It comes in a small bottle that usually contains 50-100 strips depending on the type you choose. It’s very thin, and on one end there’s a small square of paper (this is the end you dip in the urine). If there are ketones in your urine, the little paper will change color. The darker it is (light pink up to a purple color) the more it is in your urine. On the bottle, there’s a picture you compare the color of the paper with that can be a very good indication of your current ketone state. 

I think almost everyone agrees with me when I say that the ketogenic diet is probably one of the most complex and difficult eating plans out there. Even when you’re not on a diet or trying to lose weight you still have to bring a lot of attention to detail. Getting into ketosis isn’t as important as we would think, but there are still 5 simple steps we can make to get into a ketotic state.

This process can be used as a way to get you into ketosis more quickly, so you can transition gracefully into a ketogenic lifestyle or as a way to stimulate autophagy and fat loss. If you can’t go without fat for the full 3 day fast — it’s okay — you will still illicit many of the benefits of fasting by limiting your protein and carbohydrate intake.

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.’
It might sound absolutely crazy to go that long without food. Especially when you consider traditional diets that recommend eating 3-5 small meals each day, starting with breakfast – the “most important” meal of the day. But if you think back to hunter gatherer times, human beings didn’t always have food accessible to us. Farming and agriculture hadn’t existed so our first meal each day would vary quite vastly. If you think about the word itself, ‘breakfast’ means to break-fast. We didn’t have a set time where we would consume our first meal – it was dependent on accessibility. So if you’re wondering how you’re going to survive without going for food for 16 hours, the answer is straight forward – you can! Let’s simplify this and break down what this may potentially look like.
Exogenous ketones can lower appetite during a fast. After an overnight fast, normal weight human subjects either drank a ketone ester supplement or a calorie-matched glucose drink. Compared to the glucose drinkers, the ketone drinkers had lower insulin, lower ghrelin, greater satiety, and less hunger. This can be useful for people trying to extend their fast who don’t want to or can’t yet deal with the hunger. You’re still taking in energy, but the metabolic profile remains similar to that of a fasted person.

This research is a good reminder to discuss with your doctor before taking any supplements. Given the widespread use of calcium supplements, more research is required before any final conclusions can be drawn. Several ketone companies have tried to avoid the large sodium loads but instead relied on a bump in the calcium content from the BHB ketone salts, seemingly without consideration for the aforementioned results. Calcium BHB will likely absorb slower compared to sodium BHB due to digestion and absorption kinetics.  For those looking to optimize brain uptake of ketones, this probably isn’t the best strategy (as uptake is directly proportional to the levels in the blood).   Be cautious of supplements running from the sodium and chasing the calcium BHB instead, and make sure you factor that into your overall daily needs.


Exogenous ketones drinks are growing in popularity as a method to elevate blood ketone concentrations and mimic a ketogenic diet without the need for dietary changes (Ari et al., 2016; Cox et al., 2016; Kesl et al., 2016; Caminhotto et al., 2017; Evans et al., 2017). The present study describes the pharmacokinetic and pharmacodynamics properties of ketone ester and salt drinks in humans at rest, and characterizes the effects of a prior meal, which is pertinent to use as a dietary supplement. The main findings were that KE drinks elevated blood d-βHB > 50% higher than KS drinks, the latter significantly increasing blood l-βHB, which was metabolized more slowly by the body. Both drinks had similar effects on FFA, TG, glucose and electrolyte concentrations, although with disparate effects on pH. A prior meal decreased total blood d-βHB appearance after a KE drink. Finally, either three KE drinks or nasogastric feeding effectively maintained nutritional ketosis over 1 mM for 9 h.
So if your high-fat diet includes a high amount of roasted seeds or roasted nuts, nut butters, heated oils such as heated coconut oil or heated extra virgin olive oil, barbecued meats or meats cooked at very high temperatures, then your triglyceride count is going to go up. You should have triglycerides that are less than 150mg/dL, and a triglyceride to HDL ratio that is no more than 4:1, and in most of the healthiest people I’ve worked with, triglycerides are under 100 and the triglyceride to HDL ratio is less than 2:1. If your ratio is whacked, your ketogenic diet isn’t doing you any favors.’

Animal procedures were performed in accordance with the University of South Florida Institutional Animal Care and Use Committee (IACUC) guidelines (Protocol #0006R). Juvenile male Sprague–Dawley rats (275–325 g, Harlan Laboratories) were randomly assigned to one of six study groups: control (water, n = 11), BD (n = 11), KE (n = 11), MCT (n = 10), BMS (n = 11), or BMS + MCT (n = 12). Caloric density of standard rodent chow and dose of ketone supplements are listed in Table 1. On days 1–14, rats received a 5 g/kg body weight dose of their respective treatments via intragastric gavage. Dosage was increased to 10 g/kg body weight for the second half of the study (days 15–28) for all groups except BD and KE to prevent excessive hyperketonemia (ketoacidosis). Each daily dose of BMS would equal ~1000–1500 mg of βHB, depending on the weight of the animal. Intragastric gavage was performed at the same time daily, and animals had ad libitum access to standard rodent chow 2018 (Harlan Teklad) for the duration of the study. The macronutrient ratio the standard rodent chow was 62.2, 23.8 and 14 % of carbohydrates, protein and fat respectively.
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.
Lots of good info but some things are just plain wrong. It takes 2 days max to get into ketosis if you stop eating carbs. Your body can only store roughly 2 days worth of glycogen. When those stores are exhausted your body will immediately turn to fat. It may take a week or several weeks to get “keto adapted” but it simply won’t ever take you more than 2 days to get into a state of ketosis.
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.
For the first part of my experiment, I would simply record my blood ketone and glucose levels over a period of two hours after taking the ketone esters. While I am already fairly keto-adapted and can attain nutritional ketosis fairly easily (> 0.5 mmol/L), it wasn’t until the end of my Five-day Fasting Mimicking Diet that I was even close to reaching therapeutic ketosis levels (>5.0 mmol/L).
Skipping breakfast on a keto diet is a popular way to boost ketone levels. Despite the age-old myth that breakfast is the most important meal of the day, research shows that breakfast skipping is not only safe but beneficial. Skipping breakfast causes intermittent ketosis and also suppresses appetite [6]. Make sure your next meal of the day isn't too late in the evening as studies show that eating meals late at night causes weight gain and impairs fat metabolism [7].
Plus, take a look at this promotional video from Prüvit. It claims that “ketones make the fat melt off your body”, which is simply not true (I’ll get back to this later). It also claims that if you wanted to reach ketosis naturally, you would either need to work out 10x harder and longer or be like one of the “extreme people” who “biohack their bodies” to get into ketosis, which “can take weeks or months”. For me, this is irresponsible. A keto diet can be simple and enjoyable, but this video makes switching to a healthy, real food, keto diet sound extreme and difficult while promoting an easy way out in the form of a drink. And that’s just bad advice.
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.
A meal high in carbohydrate and calories significantly decreased peak d-βHB by ~ 1 mM (Figure ​(Figure4A)4A) and reduced the d-βHB AUC by 27% (p < 0.001, Figure ​Figure4B).4B). There were no significant changes in d-βHB Tmax (fed = 73 ± 6 min vs. fasted 66 ± 4 min). Despite the differences in d-βHB kinetics after the meal, there were no effects of food on urinary ketone excretion (Figure ​(Figure4C),4C), plasma AcAc (Figure ​(Figure4D)4D) or breath acetone (Figure ​(Figure4E)4E) following KE ingestion. Plasma AcAc kinetics followed a similar time course to d-βHB, with the ratio of blood d-βHB: AcAc being 6:1 when KE drinks were consumed whilst fasted, and 4:1 following the meal. As observed in Study 1, breath acetone concentrations rose more slowly than blood ketone concentrations, reaching a plateau at 150 min and remaining elevated for at least 4 h (Figure ​(Figure4E4E).

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.
Comments are welcomed and encouraged. The purpose of comments on our site is to expand knowledge, engage in thoughtful discussion, and learn more from readers. Criticism and skepticism can be far more useful than praise and unflinching belief. There’s an art and science to critical thinking and how to conduct yourself. There’s a multitude of fallacious appeals we could spell out, but a good rule of thumb is not to attack the person, attack the ideas. Don’t look for the flaws in the person, look for the flaws in the hypothesis. Let’s keep the brawling to movies depicting minor league hockey teams and political “news” shows. Thank you for adding to the discussion.

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