The ‘carb-sparing’ effect from BHB suppresses the break down of muscle glycogen. This leads to lower lactate levels. When increasing exercise intensity, fat oxidation (burning) reaches a limit. At that point the muscle burns carbohydrates as fuel. But when consuming Ketone esters, the body does not make this switch. This suggests Ketones are being used instead. 11

In Summary, I think it’s important to do your own research and draw your own conclusion about the long term risks of ketosis. For some people, a ketogenic diet may be a necessity given their health situation. For those of us who do not suffer from such health conditions I would present the question ‘why do you want to follow a strict ketogenic diet for an extended period’, and then follow this up with ‘are the potential risks and sacrifices worth the benefits?’
Ketones may be a better source of fuel than glucose, and a far better beverage than Fruitopia, but it's a question of whether or not you can spare the extra fuel. Because just like adding sugar to a diet, it's like pressing pause on the fat burning process since the body preferentially burns it for fuel. Adding ketones to the diet does the same thing.
A recent study, Ketone Bodies Mimic the Life Span Extending Properties of Caloric Restriction, showed the effects of exogenous ketones on longevity (ketone esters, specifically) and concluded that ketones should be labeled as an “anti-aging” compound (suggesting that the real reason caloric restriction has been shown to extend life span is actually due to resulting ketosis).

Some people follow more of an Ultra Low Carb diet approach. This is generally around 50g or less of carbs per day. A ULC is more supportive of reaching a ketogenic state, but again total carbs are not the only variable when it comes to reaching ketosis (other factors such as types of carbs, protein consumption, portion size, ingredients, supplements used etc. all play a role and will be covered in more detail below). 
I just read your comment and was wondering the same thing. I can see how exogenous ketones can be a great energy boost to people on the ketogenic diet, but I don’t see how they can speed fat loss. Keto OS claims you can eat higher carbs and still see the benefits of ketosis. I don’t see how that is possible. the whole point of weight loss through ketosis is the breaking down of your own fat to create energy. I don’t see how exogenous energy will increase natural fat breakdown. I wish I could get a straight answer to this from somebody.
Onnit is an incredible company that’s making a massive impacts in the lives of athletes in nearly every sport. From Olympic Gold Medalists, to NFL middle linebackers, Onnit has taken athletic performance to a new level. Providing supplements, food, and training equipment, Onnit was an early adopter of the elite performance booster that is exogenous ketones!
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
Two ground-breaking studies have recently been published on the effects of intermittent fasting on males. One group of researchers studied the effects that 16 hours of intermittent fasting had on males that lift weights. They found that muscle mass stayed the same, fat mass decreased significantly, and the males who fasted for 16 hours a day burned more fat for fuel compared to the control group that only fasted for 12 hours.
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 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.
We tested the effects of 28-day administration of five ketone supplements on blood glucose, ketones, and lipids in male Sprague–Dawley rats. The supplements included: 1,3-butanediol (BD), a sodium/potassium β-hydroxybutyrate (βHB) mineral salt (BMS), medium chain triglyceride oil (MCT), BMS + MCT 1:1 mixture, and 1,3 butanediol acetoacetate diester (KE). Rats received a daily 5–10 g/kg dose of their respective ketone supplement via intragastric gavage during treatment. Weekly whole blood samples were taken for analysis of glucose and βHB at baseline and, 0.5, 1, 4, 8, and 12 h post-gavage, or until βHB returned to baseline. At 28 days, triglycerides, total cholesterol and high-density lipoprotein (HDL) were measured.
I (Kim) researched the topic and planned and ran the experiment under the guidance and supervision of Dr. Andreas Eenfeldt, who touched base with me every step of the way to check the experiment design and execution for scientific rigor (to the greatest degree possible) and who has edited this writeup for quality and trustworthiness reasons. I also consulted with other keto experts and researchers to gather feedback both on the experiment design and the results data. They are referenced in the text when this was the case.
I followed 30g carbs as my limit each day, moderate protein, increased fat intake (avocado at each main meal plus carefully chosen oils, eggs and nuts) and have upped green veg to the bucket load and incorporated a juiced lemon in water to my morning, as well as my usual water consumption. I also did intermittent fasting Mon to Thur, 18 hours fasting each day.
Participants consumed 13.2−1 of βHB (6.6−1 or 1,161 mg/kg of KE) over 9 h, either as 3 drinks of 4.4−1 of βHB at 3 h intervals (n = 12), or as an initial bolus of 4.4−1 of βHB given through a nasogastric tube, followed by an infusion of 1.1−1, beginning 60 min after the initial bolus, for 8 h (n = 4). Two participants completed both conditions (total n = 14). In both conditions, the KE was diluted to 1.5 L using the same citrus water as used in Study 2.
Possible GI distress (flatulence) at exceptionally high doses –  In the studies referenced in this article, exogenous ketones taken in large doses occasionally resulted in GI distress, especially flatulence. However, the cause of this is hypothesized to be due to the fact that ketones were mixed in a milky fluid that wasn’t very palatable. If you’re taking a nominal dose of exogenous ketones the likelihood of GI distress is rather low. Moreover, if some GI distress is prevalent, it should improve as you become accustomed to taking ketones.

If you stop eating carbs, your body first uses up glucose reserves stored in the liver and muscles. After it burns all that's left of glucose, it has no other options but to start burning fat. It can burn either your body's fat stores or the fat you eat. However, not all cells in your body can use fat to make energy and this is where ketones come into play.
Methods and Results: In the first study, 15 participants consumed KE or KS drinks that delivered ~12 or ~24 g of βHB. Both drinks elevated blood D-βHB concentrations (D-βHB Cmax: KE 2.8 mM, KS 1.0 mM, P < 0.001), which returned to baseline within 3–4 h. KS drinks were found to contain 50% of the L-βHB isoform, which remained elevated in blood for over 8 h, but was not detectable after 24 h. Urinary excretion of both D-βHB and L-βHB was <1.5% of the total βHB ingested and was in proportion to the blood AUC. D-βHB, but not L-βHB, was slowly converted to breath acetone. The KE drink decreased blood pH by 0.10 and the KS drink increased urinary pH from 5.7 to 8.5. In the second study, the effect of a meal before a KE drink on blood D-βHB concentrations was determined in 16 participants. Food lowered blood D-βHB Cmax by 33% (Fed 2.2 mM, Fasted 3.3 mM, P < 0.001), but did not alter acetoacetate or breath acetone concentrations. All ketone drinks lowered blood glucose, free fatty acid and triglyceride concentrations, and had similar effects on blood electrolytes, which remained normal. In the final study, participants were given KE over 9 h as three drinks (n = 12) or a continuous nasogastric infusion (n = 4) to maintain blood D-βHB concentrations greater than 1 mM. Both drinks and infusions gave identical D-βHB AUC of 1.3–1.4 moles.min.

Ketosis is a unique metabolic state where your body burns fat instead of glucose for fuel. Glucose is a simple sugar molecule derived from carbohydrates. Your body prefers using glucose to using fat and protein to make energy. This is because glucose it is easy to burn as it doesn't require much energy. On the other hand, your body uses fat and protein to build and repair tissue and make hormones.

However, we will not be commenting on ketone esters since there are big differences between them and ketone salts, and the ketone salts are the ones that have been heavily commercialized and marketed to the public over recent years. Ketone esters may be more difficult to market due to their having an unpleasant taste. We may look more deeply into the esters in the future.
Hypoglycemia: why not to be concerned – Taking exogenous ketones can drive blood glucose levels quite low, but you are not likely to feel the typical symptoms of hypoglycemia. This is because when ketone levels are high enough, they dominate as fuel in the brain; hence, you will feel just fine despite having low blood glucose. A highly-cited study by George Cahill, found elevated ketone levels could protect fasted participants when they were administered insulin to induce hypoglycemia.
My two cents: I wouldn’t take ketone supps if not on some sort of low(ish) carb diet because the idea of high levels of BOTH fuels (ie, ketones AND glucose) doesn’t seem physiologically appropriate… more like a recipe for disaster, and by “disaster,” I mean “out-of-control production of Reactive Oxygen Species” — this might not matter if you’re an athlete looking for a quick performance boost, because the fuels are going to be cleared rather quickly… not so much if you’re a desk jockey.
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).

Every 7 days, animals were briefly fasted (4 h, water available) prior to intragastric gavage to standardize levels of blood metabolites prior to glucose and βHB measurements at baseline. Baseline (time 0) was immediately prior to gavage. Whole blood samples (10 μL) were taken from the saphenous vein for analysis of glucose and βHB levels with the commercially available glucose and ketone monitoring system Precision Xtra™ (Abbott Laboratories, Abbott Park, IL). Blood glucose and βHB were measured at 0, 0.5, 1, 4, 8, and 12 h after test substance administration, or until βHB returned to baseline levels. Food was returned to animals after blood analysis at time 0 and gavage. At baseline and week 4, whole blood samples (10 μL) were taken from the saphenous vein immediately prior to gavage (time 0) for analysis of total cholesterol, high-density lipoprotein (HDL), and triglycerides with the commercially available CardioChek™ blood lipid analyzer (Polymer Technology Systems, Inc., Indianapolis, IN). Low-density lipoprotein (LDL) cholesterol was calculated from the three measured lipid levels using the Friedewald equation: (LDL Cholesterol = Total Cholesterol - HDL - (Triglycerides/5)) [51, 52]. Animals were weighed once per week to track changes in body weight associated with hyperketonemia.

If you read about ketosis in magazine or heard about it in a podcast and wanted to jump on the bandwagon, then I think you should avoid it. Remember, it is a strict diet, and the potential health downsides may not be worth the upsides, unless you are working with a medical professional and or you are tracking your labs to see what’s going on with your health (thyroid).

Most of the information regarding the effects of ketosis come from studies on the ketogenic diet, wherein ketones are made by the liver and become a major fuel source for the body. The ketogenic diet is currently under investigation for its potential therapeutic effects in a number of healthy and disease states. More recently, studies are beginning to reveal that many of the effects observed with the ketogenic diet are mechanistically attributable to ketones, which is a primary reason that exogenous ketones are being developed and studied. However, because they are such a new technology, there’s not a lot of data on exogenous ketones themselves. In a few pre-clinical studies, exogenous ketones have mimicked the therapeutic effects of the ketogenic diet”
Compared to our other cellular gasoline (carbs), we can store an unlimited supply of energy from ketones in our body within our fat. When you’re reliant on carbohydrates, you’re forced to keep your tank partly full as we can only store just over 2,000 calories of glycogen from carbs. An empty carb tank results in carb-withdrawal symptoms from not being able to switch into a ketone or fat burning metabolism.
The fate of excess ketones: In the event someone has an excessive amount of ketones in the blood, the body (specifically the kidneys) will work as quickly as possible to filter out ketones via urine rather than converting them to adipose tissue.9 This is not to say that you can’t gain fat if you consume an exorbitant amount of exogenous ketones, but that they are less prone to be converted to fat than other nutrients.
Remember how important it is to measure ketone blood levels accurately? Same goes for food tracking. A food tracking app, like MyFitnessPal, provides insight into macronutrient intake and thus the ability to tweak the diet to achieve ketosis. Tracking diet (inputs) and measuring ketones levels (outputs) delivers the best shot at optimizing the keto diet plan.
Those new to keto should be testing to see if their bodies are in ketosis, regardless of method. Testing, in general, is the most objective way to know if you’re in ketosis. There can be some subjective benefits of ketosis: appetite suppression, fat loss, low blood sugar, improvement in mental cognition and focus. But before recognizing these subjective benefits, it’s important to track and measure the level of ketones in the blood to ensure ketosis on a physical level.
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.

Ketosis is a metabolic state where most of the body’s energy supply comes from ketone bodies in the blood, in contrast to a state of glycolysis where blood glucose provides most of the energy. Ketosis is characterised by serum blood concentrations of ketone bodies over 0.5 millimolar with low and stable levels of insulin and blood glucose. However, with ketone supplementation (as you’ll learn about later in this article) ketosis can actually be induced even when there are high levels of blood glucose

Taking exogenous ketones not only eliminates the need to follow a strict ketogenic diet to achieve ketosis (so you can have your high carb cake and eat it too), it can also help users get there faster. “They can expedite the process of getting into ketosis and becoming fat adapted,” Davis explains. “They can also help people push past the keto flu and potentially experience more mental energy and clarity than from diet alone.”
Today, 4/27, I received the Peaches & Cream. I was reluctant to purchase, but I didn't want to wait until Saturday for the Salted Chocolate. After dinner, I mixed it in water, added heavy cream, put it over ice. Delicious!!! I believe these products work bc I can still eat up to 50-100g of carbs on a lax day and still drop weight since it keeps me in Ketosis.

We sampled each of the 3 flavors and also mixed in the available Ketōstax and this supplement tasted better than any other we had tried. Ketōnd costs $79.95 for 30 servings which is about $2.67 per serving – which is less than half the price of the leading competitor. Ketōnd’s label and ingredients are 100% transparent, so they disclose everything that is in the supplement – which is only ketones. What we really liked about Ketōnd is that it isn’t part of some Multi Level Marketing company so there are no obligations.
SHEER Ketones BHB Salts made this top 5 list because they do a good job of avoiding all the common unwanted additives and fillers in BHB salts. It’s good to see we have options to choose from when trying to avoid these types of ingredients. SHEER Ketones’ other ingredients include citric acid, fruit and vegetable juice powder for the color, and “natural flavors.” It uses a stevia leaf extract (Rebaudioside A).
Bottom line: EK isn't the magic pill for instant weight loss. EK triggers ketosis which is a metabolic state where your body burns fat for fuel. EK increases satiety and feeling full, and boosts energy for exercise which helps you lose weight for the long term. You should always aim for the long term and sustainable weight loss and keep the weight off for good instead of looking for a quick fix.
When choosing an exogenous ketone supplement, make sure to read the ingredients carefully. Brands that have a “proprietary blend” don’t allow you to see the quantities of each ingredient in their mix. You should know every detail about the supplements you choose, so you know exactly what is affecting your body, and you have control over the variables of your intake.
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