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.
Beta hydroxybutyrate floats around in your blood, and importantly, can cross different barriers to be able to be turned into energy at all times. One of the most important areas where this happens is in the brain. The blood-brain barrier (BBB) is usually a very tightly regulated interface that doesn’t allow the transfer of many molecules, but since BHB is such a rock star and so hydrophilic, your brain knows to let it in so it can bring energy to the party at any time. This is one of the main reasons why increased levels of ketosis lead to improved mental clarity, focus and reduction in neurodegenerative diseases.
First, there’s something unnatural about having elevated levels of ketones and glucose together. It’s really hard to make that happen using traditional whole foods. The closest natural approximation you could get to it would be the traditional coconut-rich diets of the Kitava people in the South Pacific, where the medium chain triglycerides (MCT) in the coconut fat increased ketone production alongside the carbs in the fruit and tubers they ate. They had excellent metabolic health, but they weren’t anywhere close to a ketogenic diet. Coconut fat isn’t as ketogenic as purified MCT oil, let alone exogenous ketones.

When your body is done using up a certain substrate to create energy (acetyl-CoA) after eating carbohydrates, it will start to find creative ways to get the job done. This is something that you want to happen. This is the switch to ketosis. If you didn’t do this, you’d be dead after fasting for a very short period of time. Under normal circumstances, the liver will start making beta-hydroxybutyrate from long chain and medium chain fatty acids that are liberated from your fat tissue. You are turning fat into fuel. Good work. This is why people can fast for months at a time and still function like normal humans.

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.
In the second of these posts I discuss the Delta G implications of the body using ketones (specifically, beta-hydroxybutyrate, or BHB, and acetoacetate, or AcAc) for ATP generation, instead of glucose and free fatty acid (FFA). At the time I wrote that post I was particularly (read: personally) interested in the Delta G arbitrage. Stated simply, per unit of carbon, utilization of BHB offers more ATP for the same amount of oxygen consumption (as corollary, generation of the same amount of ATP requires less oxygen consumption, when compared to glucose or FFA).
So long long does it take to get into ketosis? This transition could take anywhere from 48 hours to one week. The length in time will vary depending upon your activity level, lifestyle, body type and carbohydrate intake. There are several ways you can speed up this process, like intermittent fasting, drastically decreasing your carb intake and supplementation.
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.
When you restrict carbs, the kidneys excrete a lot of sodium. Not replacing this sodium can leave you feeling light headed. I recommend having a big glass of spring water with ½ teaspoon of Celtic sea salt twice a day (first thing in the morning and midafternoon are two times that work well). A long with this, make sure you use a lot of salt on your meals.
The difference in peak blood d-βHB concentrations between matched amounts of βHB as ester or salts arose because the salt contained l-βHB, as the blood concentrations of d- plus l-βHB isoforms were similar for both compounds. It is unclear if kinetic parameters of KE and KS drinks would be similar if matched d-βHB were taken in the drinks. Unlike d-βHB, blood l-βHB remained elevated for at least 8 h following the drink, suggesting an overall lower rate of metabolism of l-βHB as urinary elimination of l-βHB was in proportion to plasma concentration. Despite similar concentrations of total βHB, breath acetone was ~50% lower following KS drinks compared to KE, suggesting fundamental differences in the metabolic fates of D- and L-βHB. These findings support both previous hypotheses (Veech and King, 2016) and experimental work in rats (Webber and Edmond, 1977), which suggested that the l-isoform was less readily oxidized than the d-isoform, and is processed via different pathways, perhaps in different cellular compartments. It seems that l-βHB is not a major oxidative fuel at rest, and may accumulate with repeated KS drinks. However, the putative signaling role of l-βHB in humans remains unclear. In rodent cardiomyocytes, l-βHB acts as a signal that modulates the metabolism of d-βHB and glucose, Tsai et al. (2006) although no differences in blood glucose were seen here. Furthermore, L-βHB can act as a cellular antioxidant, although to a lesser extent than D-βHB (Haces et al., 2008).
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.
Effects of ketone supplementation on body weight: Rats administered ketone supplements gained less weight over the 4-week period; however, did not lose weight and maintained healthy range for age. KE supplemented rats gained significantly less weight during the entire 4-week study compared to controls. BMS + MCT, BMS, and BD supplemented rats gained significantly less weight than controls over weeks 2–4.MCT supplemented rats gained significantly less weight than controls over weeks 3–4, Two-Way ANOVA with Tukey’s post hoc test, results considered significant if p < 0.05. Error bars represent mean (SD)
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]
“Imagining that everyone is going to go on a ketogenic diet is very unlikely. I’ve done it myself, and it is hard as a diet to sustain for a long period of time,” said Verdin. “The interest for us in BHB is [if] can we recapitulate all the beneficial effects that we are seeing from the ketogenic diet simply by administering BHB as a food or as a drug, whatever you want to call it.”
There’s debate raging about which dietary tactic is the god particle for making you leaner, faster and healthier. How the ketogenic diet option squares off against the low carb route is vital for understanding the ways in which exogenous ketone supplements work. To get into ketosis the natural way, you need to keep your carb intake low enough for long enough for your body to begin using use fat as fuel. Your liver then converts a portion of that fat into energy molecules called ketones. These work together with glucose as a fuel source, but can actually kick in faster, allowing your body to operate more economically during lengthy, high-energy exercise efforts.
As stated above, there appears to be a difference between supplemental and dietary calcium intake, which can be important to keep in mind.  One study found aggregate calcium intakes above 1400 mg per day (from dietary and supplemental intake combined) to be associated with higher death rates, cardiovascular disease, and ischemic heart disease in women[15]. A 2014 meta-analysis found an association between dietary calcium intake and cardiovascular mortality[16]. The meta-analysis actually found a u-shaped relationship, where dietary calcium intakes that were both lower and greater than 800 mg/day were gradually associated with increased risk of cardiovascular mortality.
The year before last I somehow full on Rocked at the keto diet lost 100lb, and was taking adderall. I am transitioning back into it again also back on the adderall, but i seem to have no energy and last time my doc did my blood work i was only 16% hydrated. Obviously it’s a huge problem for me, staying hydrated and trying to lift the fogginess. I am type 2 diabetic and my doctor is on board with me trying all to keep my sugars down YEAH!!! I have never tried any exogenous product. My body seems to not absorb much vitamins. Can anyone make a or any suggestion to me as to how to get this under control?
Over five visits, participants (n = 16) consumed either 4.4−1 of βHB (2.2−1 or 395 mg/kg of KE; 1 mole of KE delivered 2 moles of d-βHB equivalents): twice whilst fasted, and twice following a standardized meal, or an isocaloric dextrose drink without a meal. To improve palatability, drinks were diluted to 500 ml with a commercially available, citrus flavored drink containing 65 kCal (5 g of carbohydrate) (Glaceau, UK). The dextrose drink was taste-matched using a bitterness additive (Symrise, Holzminden, Germany). The standard meal consisted of porridge oats (54 g), semi-skimmed milk (360 ml) and banana (120 g), giving 600 kCal per person, with a macronutrient ratio of Carbohydrate: Protein: Fat of 2:1:1.
Exogenous ketones are ketones that come in the form of a powder that you mix with water to drink them. Exogenous ketones are controversial in the keto world. The problem is the marketing of them have made some people believe that all they have to do is use this product to get into ketosis. If your blood glucose is too high your body will not use the ketones and they will go to waste.
Not only is Ketōnd considered one of the best on ketone supplements the market it also currently holds favorable ratings, reaching numbers as high as 98 percent in customer reviews. They absolutely love this product and you will too if you give it a try. You will get some incredible results. Whether you are a busy professionals, athlete, on-the-go moms or dads, or college students you too will love this product.
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.
Ketogenic Diets and Physical Performance – Impaired physical performance is a common but not obligate result of a low carbohydrate diet. Lessons from traditional Inuit culture indicate that time for adaptation, optimized sodium and potassium nutriture, and constraint of protein to 15–25 % of daily energy expenditure allow unimpaired endurance performance despite nutritional ketosis. (
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.
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.

Humans in the hunter-gatherer era survived thanks to metabolic flexibility — the body’s ability to use different fuels for energy depending on the nutrients available. This adaptation was vital during a time when the source, quantity, and frequency of food was uncertain[*]. Most of the time, people were fasting, so their bodies ran on ketones, not glucose.

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