Exogenous ketones don’t seem to improve high-intensity, glucose-intensive exercise, increasing fat burning during steady state exercise but dropping top-end high-intensity performance. Another study found that ketone dieters reduced 50-minute time trial performance in cyclists, though another group of researchers have criticized the methods. Even when a ketone ester didn’t improve performance in the shuttle run to exhaustion and 15 meter sprint repeats, it did reduce the drop in brain function following the exercise.
Your brain has a very tight barrier so not everything in the blood can get through. This is called the blood brain barrier. Because your brain uses 25% of the energy that your entire body uses throughout the day, you need to make sure it is fueled appropriately. Glucose can’t directly cross the blood brain barrier. When you eat carbs, you get swings in energy that is available to cross the blood brain barrier which leads to mental fog.
That’s not all. Though Prüvit in particular has a legion of fans (the brand has nearly 35,000 Instagram followers and some 256,000 likes on Facebook) and a small team of affiliated medical experts, there’s no hard science on Prüvit or similar products. (Prevention reached out to several Prüvit experts and employees for interviews but did not receive a response.) The research page on the brand’s website does include links to legit scientific studies. But the studies are on the keto diet—not on Prüvit’s products. When it comes to research on the actual supplements, the brand’s website simply says “Human studies on finished products (underway) at various universities and research facilities.” In other words, there’s no scientific evidence available yet to show that they actually work.
Before that though, I do want to touch on MCT oil and it’s impact on ketone levels. MCT – or Medium Chain Triglyceride – are fatty acids that bypass the liver – and become quick energy for the brain and muscles. As they are a fat based energy source (and not a carbohydrate) they are quickly converted into ketones. This means MCT oil is a great way to boost ketone levels in the body.

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.

On day 29, rats were sacrificed via deep isoflurane anesthesia, exsanguination by cardiac puncture, and decapitation 4–8 h after intragastric gavage, which correlated to the time range where the most significantly elevated blood βHB levels were observed. Brain, lungs, liver, kidneys, spleen and heart were harvested, weighed (AWS-1000 1 kg portable digital scale (AWS, Charleston, SC)), and flash-frozen in liquid nitrogen or preserved in 4 % paraformaldehyde for future analysis.
A typical serving of racemic ketone salts contains around 12g of beta hydroxybutyrate, of which only half is the D- form (6g). Compared to the 40g ketone esters I consumed (which are 100% D- form), I would need to consume somewhere around seven to nine packets of ketone salts to get the same amount of D-β-hydroxybutyrate (some D- form is wasted burning of the L- form), along with the huge amount of salts contained and more than a gallon of water (since the powders must be mixed). Even if one could consume that amount of ketone salts, they will probably suffer from what people often refer as “disaster pants” (aka diarrhea) due to the amount of salt consumed.
More tolerable than MCT oil: MCT oil has been known to cause gastrointestinal distress in users, especially when taken in higher amounts. Exogenous ketones in the form of ketone salts, in comparison, are well-tolerated. Thus they enable one to avoid adverse GI events while providing the body with similar types of benefits. Figure 2 shows Ketone esters can be effective at reducing appetite. A combination of MCT oil and exogenous ketones may aid weight loss and allow a lower loading of ketone supplements, without the GI distress seen with MCT oil.
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

 “Though the small amount of carbohydrates in the diets may be more than balanced by the potential sugar production from the large amount of protein to keep the ratio of fatty acid to glucose below the generally accepted level of ketogenesis, the respiratory quotient data suggest another mechanism also” ß (most likely the CPT-1A mutation, which had not been discovered at that time)
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.
That’s exactly what ketones do: inhibit lipolysis, the breakdown of body fat into triglycerides and free fatty acids for burning. In normal conditions where ketones are produced endogenously, this is expected and beneficial. If homemade ketones increased lipolysis, you’d end up with ketoacidosis. You’d make ketones which released more body fat which got turned into more ketones which released more body fat which became more ketones. And on and on. It simply wouldn’t stop.

Exogenously delivered ketone supplements significantly altered rat weight gain for the duration of the study (Fig. 6). However, rats did not lose weight and maintained a healthy range for their age. Rats have been shown to effectively balance their caloric intake to prevent weight loss/gain [97–99]. Due to the caloric density of the exogenous ketone supplements (Table 1) it is possible for the rats to eat less of the standard rodent chow and therefore less carbohydrates while maintaining their caloric intake. Food intake was not measured for this study. However, if there was a significant carbohydrate restriction there would be a signifcant change in basal blood ketone and blood glucose levels. As the hallmark to the KD, carbohydrate restriction increases blood ketone levels and reduces blood glucose levels. Neither an increase in basal blood ketone levels nor a decrease in basal blood glucose levels was observed in this study (Fig. 7). Additionally, if there were an overall blood glucose decrease due to a change in food intake, this would not explain the rapid reduction (within 30 min) in blood glucose correlated with an elevation of blood ketone levels after an intragastric bolus of ketone supplement (Figs. 2, ​,33 and ​and44).


Anti-carcinogenic properties: Data seems to suggest that exogenous ketones are an effective anti-carcinogen. The reason behind this is that cancer cells are unable to use ketone bodies effectively, unlike most healthy tissues in the body. In fact, dietary ketone supplementation has been shown to increase survival rates of mice with systematic cancer by as much as 70%.17
And zero-carb, followed by fasting for two meals, and then followed up by a second zero-carb meal is almost always all you need to get into ketosis fast. By Sunday or Monday morning, after a second night of no carbs, you’ll be in a deep enough ketosis that hunger will crash and your energy will surge to help you transition into your low-carb diet of choice.

Here we investigated the effects of KE and KS consumption on blood βHB and metabolite concentrations. As we found that KE ingestion delivered a >50% higher plasma concentrations of d-βHB alone, we subsequently determined the reliability and repeatability of ketosis following KE consumption and the effects of concomitant meal ingestion on blood ketone and substrate kinetics. Finally, we determined whether nasogastric infusion could be used for KE administration, given that some patients require feeding in this manner.
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.
BS, KC, and PC designed the research studies. BS, PC, RE, SM, and PS carried out the studies. SH provided the gas analyser used in the study on behalf of NTT DOCOMO Inc. BS, MS, and SM analyzed the data and performed statistical analysis in collaboration with JM. BS wrote the paper with help from KC, PC, and OF. KC had primary responsibility for final content. All authors read and approved the final manuscript.

Over the years, we have seen and heard many different things about the effects and benefits of Raspberry Ketone supplements. Be it capsules or sprays, the discussion around them actually working always had opposing sides. So, we decided the best solution was to do our own research by conducting our own reviews on the most talked about products, to find out exactly how good they were as a "top-rated" ketone supplement.
LDL is the lipoprotein particle that is most often associated with atherosclerosis. LDL particles exist in different sizes: large molecules (Pattern A) or small molecules (Pattern B). Recent studies have investigated the importance of LDL-particle type and size rather than total concentration as being the source for cardiovascular risk [56]. Patients whose LDL particles are predominantly small and dense (Pattern B) have a greater risk of cardiovascular disease (CVD). It is thought that small, dense LDL particles are more able to penetrate the endothelium and cause in damage and inflammation [82–85]. Volek et al. reported that the KD increased the pattern and volume of LDL particles, which is considered to reduce cardiovascular risk [73]. Though we did not show a significant effect on LDL levels for ketone supplements, future chronic feeding studies will investigate the effects of ketone supplementation on lipidomic profile and LDL particle type and size.
There’s some support that exogenous ketones can be helpful for people already dutifully following the keto diet — but research has been limited. One thing we know for sure: These aren’t a get-thin-quick solution. “I think people are drawn to a quick, easy fix, kind of a magic bullet supplement, and it’s not that this won’t contribute to weight loss, but it’s not that magic bullet,” Griffin says.
The “BHB salt” is simply a compound that consists of sodium (Na+), potassium (K+), and the ketone body β-hydroxybutyrate.  In supplements like Pruvit’s Keto OS  these individual components are being held together by ionic bonds; however, when you consume the product, it is absorbed into the blood where it dissociates into free Na+, K+, and BHB since it is a water-based solution.  Thus, consuming the product directly and immediately puts more ketones into your blood.
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.)
Ketostix are very unreliable. There are many factors which can alter results such as hydration level, if you’ve worked out recently and the amount of unused ketones in your body to name just a few. Never rely of Ketostix to determine whether you are in ketosis or not. The Precision Xtra blood ketone monitor is the gold standard for testing for ketones in your body. After following a ketogenic diet for a while, you should be able to tell if you are in ketosis or not by the way you feel.
There’s some support that exogenous ketones can be helpful for people already dutifully following the keto diet — but research has been limited. One thing we know for sure: These aren’t a get-thin-quick solution. “I think people are drawn to a quick, easy fix, kind of a magic bullet supplement, and it’s not that this won’t contribute to weight loss, but it’s not that magic bullet,” Griffin says.

I had heard horror stories about how bad ketone esters tasted (like “rocket fuel”!) so was prepared for the worst. I followed their instructions and drank the contents of the bottle in one gulp, then chased it with a sip of sparkling mineral water. While not the most pleasant aftertaste, the flavor wasn’t any worse than after a shot of well tequila. Within 15 minutes I was already well into therapeutic ketosis, and after 30 minutes my ketone meter displayed a “HI” error message (meaning my level was greater than 8.0 mmol/L)!


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.
Ketostix are very unreliable. There are many factors which can alter results such as hydration level, if you’ve worked out recently and the amount of unused ketones in your body to name just a few. Never rely of Ketostix to determine whether you are in ketosis or not. The Precision Xtra blood ketone monitor is the gold standard for testing for ketones in your body. After following a ketogenic diet for a while, you should be able to tell if you are in ketosis or not by the way you feel.
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).

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