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.
In conclusion, drinks containing exogenous ketones, in either ester or salt form, can raise concentrations of blood βHB in humans, although elevation of l-βHB lasts longer after racemic KS consumption. Both KE and KS drinks mildly altered acid-base balance. Exogenous ketones lowered blood glucose and lipids without inhibiting endogenous insulin secretion. The KE delivered highly repeatable blood concentrations of d-βHB, although ketosis was decreased by a meal. Uptake and elimination of d-βHB were similar when several drinks were consumed in succession. The dietary KE could maintain ketosis using drinks taken regularly around a normal meal pattern, or using a continuous infusion via a nasogastric tube. Therefore, ketone drinks are a viable and practical alternative to dietary strategies to achieve ketosis.
Blood glucose concentrations are decreased during both exogenous and endogenous ketosis, although by different mechanisms. During endogenous ketosis, dietary carbohydrate deficit is the underlying cause of low blood glucose, along with reduced hepatic gluconeogenesis and increased ketone production (Cahill et al., 1966). With exogenous ketosis, carbohydrate stores are plentiful, yet ketones appear to lower blood glucose through limiting hepatic gluconeogenesis and increasing peripheral glucose uptake (Mikkelsen et al., 2015). One clinical use of the ketogenic diet is to improve blood glucose control, yet the elevated blood FFA may increase the risk of heart failure (Holloway et al., 2009). Thus, the ability of exogenous ketones to lower blood glucose without elevating blood FFA concentrations could deliver the desired effect of the diet, whilst also decreasing a potential risk.
Taking MCT oil (medium chain triglyceride) or coconut oil (contains 60% MCT) can help boost ketone production. This is because your body absorbs MCT very quickly as it bypasses the gallbladder and into the liver to be processed into ketone bodies. Make sure you’re getting unprocessed versions of coconut oil that is labelled as ‘organic’ or ‘extra virgin’. This, along with grass-fed butter, is what I add into my ‘bulletproof’ coffees.
The problem? Exogenous ketone supplements work by flooding your bloodstream with ketones. But unless you’re also eating a ketogenic diet (and producing a steady stream of ketones naturally), those supplemental ketones won’t stick around forever. “The benefit of exogenous ketones is limited due to their excretion through the urine,” explains Madge Barnes, MD, family medicine specialist with Texas Health Family Care. In other words? They’ll only work for a few hours until you pee them out. As a result, you need to keep on supplementing—which can get expensive. Twenty single-serving packets of Prüvit’s Keto//OS MAX Pure Therapeutic Ketones, for example, cost $130. (The company doesn’t specify how often you should take them.)
I’m fasting (5 days fast, 2 days food) in an effort to aggressively lose weight. For the most part, I’m not doing the water & salt-only kind of fast… as I will also drink coffee & bone broth… as well as take Perfect Keto Base. Would it be “gilding the lily” to also add MCT powder to my coffee? I’m in nutritional ketosis… ranging from 0.8 to 2.0 or thereabouts.
Over the past couple years, I’ve tried a number of ketone supplements, generally to enhance a longer fast or to offer an edge before one of my Ultimate Frisbee evenings. This Kegenix variety is one I’d recommend. I’ve also used Quest Nutrition MCT oil powder with good results as well, but there are plenty of other solid formulations to choose from.

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.

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.

Several studies have investigated the safety and efficacy of ketone supplements for disease states such as AD and Parkinson’s disease, and well as for parenteral nutrition [40, 48–50, 100–103]. Our research demonstrates that several forms of dietary ketone supplementation can effectively elevate blood ketone levels and achieve deleted: therapeutic nutritional ketosis without the need for dietary carbohydrate restriction. We also demonstrated that ketosis achieved with exogenous ketone supplementation can reduce blood glucose, and this is inversely associated with the blood ketone levels. Although preliminary results are encouraging, further studies are needed to determine if oral ketone supplementation can produce the same therapeutic benefits as the classic KD in the broad-spectrum of KD-responsive disease states . Additionally, further experiments need to be conducted to see if the exogenous ketone supplementation affects the same physiological features as the KD (i.e. ROS, inflammation, ATP production). Ketone supplementation could be used as an alternative method for inducing ketosis in patients uninterested in attempting the KD or those who have previously had difficulty implementing the KD because of palatability issues, gall bladder removal, liver abnormalities, or intolerance to fat. Additional experiments should be conducted to see if ketone supplementation could be used in conjunction with the KD to assist and ease the transition to nutrition ketosis and enhance the speed of keto-adaptation. In this study we have demonstrated the ability of several ketone supplements to elevate blood ketone levels, providing multiple options to induce therapeutic ketosis based on patient need. Though additional studies are needed to determine the therapeutic potential of ketone supplementation, many patients that previously were unable to benefit from the KD may now have an alternate method of achieving therapeutic ketosis. Ketone supplementation may also represent a means to further augment ketonemia in those responsive to therapeutic ketosis, especially in those individuals where maintaining low glucose is important.
If you have been reading the science behind the ketogenic diet, you know there can be a lot of benefits associated with choosing this way of eating. There is usually a transition period from when someone chooses to go on a ketogenic diet and implements the changes to their menu to when they actually get into ketosis and are able to produce and burn ketones for fuel.

If you do the same calculations as I did above for estimating fat oxidation, you’ll see that EE in this case was approximately 13.92 kcal/min, while fat oxidation was only 67% of this, or 9.28 kcal/min, or 1.03 g/min. So, for this second effort (the test set) my body did about 5% less mechanical work, while oxidizing about 25% less of my own fat. The majority of this difference, I assume, is from the utilization of the exogenous BHB, and not glucose (again, I will address below what I think is happening with glucose levels).
Effects of beta-hydroxybutyrate on cognition in memory-impaired adults. – Glucose is the brain’s principal energy substrate. In Alzheimer’s disease (AD), there appears to be a pathological decrease in the brain’s ability to use glucose. Neurobiological evidence suggests that ketone bodies are an effective alternative energy substrate for the brain. Elevation of plasma ketone body levels through an oral dose of medium chain triglycerides (MCTs) may improve cognitive functioning in older adults with memory disorders. On separate days, 20 subjects with AD or mild cognitive impairment consumed a drink containing emulsified MCTs or placebo. Significant increases in levels of the ketone body beta-hydroxybutyrate (beta-OHB) were observed 90 min after treatment (P=0.007) when cognitive tests were administered. beta-OHB elevations were moderated by apolipoprotein E (APOE) genotype (P=0.036). For 4+ subjects, beta-OHB levels continued to rise between the 90 and 120 min blood draws in the treatment condition, while the beta-OHB levels of 4- subjects held constant (P<0.009). On cognitive testing, MCT treatment facilitated performance on the Alzheimer’s Disease Assessment Scale-Cognitive Subscale (ADAS-cog) for 4- subjects, but not for 4+ subjects (P=0.04). Higher ketone values were associated with greater improvement in paragraph recall with MCT treatment relative to placebo across all subjects (P=0.02). Additional research is warranted to determine the therapeutic benefits of MCTs for patients with AD and how APOE-4 status may mediate beta-OHB efficacy. (
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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