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.’


I wrote this post at about the same time Germany won the World Cup in Rio de Janeiro in 2014. There’s been a lot of moving and shaking in the world of exogenous ketones since then, not to mention soccer. Looking back on my post, I still consider it relevant in terms of what exogenous ketones possibly can (and cannot) do for performance. In this case, to see if exogenous ketone esters provide me a “boost” by allowing me to do the same amount of work while expending less energy (and work at a relatively lower VO2) compared to no supplementation.
Exogenous ketones are becoming more popular as advancements in scientific research continue to show how they work to improve both health and performance. At first, the only options for delivering exogenous ketones were unpalatable ketone esters; however, exogenous ketones can now be taken in the form of ketone mineral salts that are more palatable and easily blended in water. Making ketone mineral salts involves combining beta-hydroxybutyrate (BHB) with mineral salts such as sodium, calcium, magnesium, or potassium. Before considering whether ketone supplements are a good option, most people immediately look at the salt load, and rightfully so. It is important to take into account the nutritional and health impact of not only the BHB but the minerals that are used to make the product.

The concentrations of blood d-βHB after KE drinks were highly repeatable whether consumed whilst fasted or fed (Figures 4F,G). The d-βHB Cmax values ranged from 1.3 to 3.5 mM when fed and 2.3 to 4.7 mM when fasted. There was no significant effect of visit order on d-βHB kinetics, with the maximal difference in d-βHB Cmax reached by one individual being 1.2 mM when fed and 1.9 mM when fasted. Approximately 61% of the variation in the data was attributable to feeding (fed vs. fasted), <1% to visit order, 16% to inter-participant variability, and the residual 24% variability due to non-specific random effects.
Exogenous ketones are not a magical fat-loss supplement, and to suggest otherwise is both factually incorrect and deliberately misleading. In fact, consuming ketones to excess can hinder rather than help fat loss! Aggressive marketing of exogenous BHB’s has helped to create a myth being believed now by millions – that simply drinking ketones each day will somehow magically melt away the pounds. The metabolic fact that unscrupulous marketers do not point out is that dietary fat (plate fat; or fat/ketones you ingest) will be burned before stored fat (body fat). So, whilst exogenous ketones can help you to mitigate hunger (and therefore help you achieve a caloric deficit) – and although they also have many other benefits (detailed below); they are not a magic wand that you can wave to achieve weight or fat loss and should not be marketed as such.
If Prüvit’s Keto OS-Max is “not a weight loss supplement” as stated in their disclaimer, why is the official website full of success stories of people who claim to have lost huge amounts of weight from taking the supplements? Ketōnd also feature a number of weight loss success stories on their site. I will get to why there is a problem with weight loss claims later on.
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.
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).

Blood d-βHB concentrations rapidly increased to a maximum of 2.8 ± 0.2 mM following the KE drink and to 1.0 ± 0.1 mM following the KS drink (Figure ​(Figure1A).1A). After the peak was reached, blood d-βHB disappearance was non-linear, and followed first order elimination kinetics as reported previously (Clarke et al., 2012b; Shivva et al., 2016). d-βHB Tmax was ~2-fold longer following KS drinks vs. KE drinks (p < 0.01, Figure ​Figure1B),1B), and KS d-βHB AUC was ~30–60% lower than the KE drink (p < 0.01, Figure ​Figure1C1C).


This was a big surprise. We were at the very least expecting that drinking a ketone supplement would cause blood ketones to rise, but an average increase of 0.33 mmol/L is very small. The supplement associated with the highest average increase in blood ketones was Prüvit’s Keto-OS Max, but it was only an increase of 0.6 mmol/L. Brianna Stubbs, the ketone researcher I consulted with, agrees that an increase of below 2.0-3.0 mmol/L is unlikely to be of much use.
Sometimes waiting for your body to make the switch from carbohydrate metabolism to beta hydroxybutyrate metabolism (aka ketosis) can be an uncomfortable and lengthy process. Another way to get beta hydroxybutyrate into your system so your body is using “clean” energy is by taking it supplementally or through nutrition. A betahydroxybutyrate supplement is what can be used in this scenario. This is an exogenous ketone. Exogenous means you get it from outside of your body. Think EX = exit = outside.
I had the chance to interview Dr. Ryan Lowery, Ph.D. about this in person. He performs some (not peer-reviewed) research on different brands of ketone salts and is listed as one of the “specialists” on Prüvit’s website. He suggested that we had perhaps ran the tests too long after the supplements were taken, stating that blood ketones tend to peak at 30 minutes. This is, however, not what Prüvit themselves state in their article on the 59-minute test, or the promise to reach ketosis in 60 minutes on the Kegenix Prime packaging. Plus, do you really want to spend up to $390/month on a product that gives you the benefits of ketosis for half an hour?
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.
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.
I wrote this post at about the same time Germany won the World Cup in Rio de Janeiro in 2014. There’s been a lot of moving and shaking in the world of exogenous ketones since then, not to mention soccer. Looking back on my post, I still consider it relevant in terms of what exogenous ketones possibly can (and cannot) do for performance. In this case, to see if exogenous ketone esters provide me a “boost” by allowing me to do the same amount of work while expending less energy (and work at a relatively lower VO2) compared to no supplementation.

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