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.
There are enticing anecdotes of supplemental ketones being used to boost human physical performance in competitive events, notably among elite cyclists. Given that BOHB can deliver more energy per unit of oxygen consumed than either glucose or fatty acids (Sato 1995, Cox 2016, Murray 2016), this makes sense. But what we do not know is if there is any required period of adaptation to the use of exogenous ketones, and thus how to employ them in training. It is clear that exogenous ketones decrease adipose tissue lipolysis and availability of fatty acids, the exact opposite to what happens on a well formulated ketogenic diet. This distinction between exogenous ketones and ketogenic diets on adipose tissue physiology and human energy balance underscores an important reason why these two ketone-boosting strategies should not be conflated.
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.
Fasting blood samples were collected prior to all interventions. Following consumption of study drinks (details below), blood, expired gas and urine samples were collected at regular intervals for 4 h. Water was freely permitted and participants remained sedentary at the test facility throughout the visit. A subset of participants returned for samples 8 and 24 h after the ketone drinks (Study 1).
Eating around 20 grams of net carbs a day is as a foolproof way to get you into ketosis a quickly as is humanly possible. However, having 50 grams of total carbs will also get you into ketosis within three days . This amount of carbs is enough to deplete glucose reserves. It's also low enough to prevent fat being used to make glucose and, instead, the body is forced to make ketones.
Most supplements rely on BHB as the source of their exogenous ketone bodies. BHB is converted to acetoacetic acid with a small quantity converted to acetone through a acetoacetate decarboxylase waste pathway. Some of the acetoacetic acid will enter the energy pathway using beta-ketothialase, which converts acetoacetic acid to two Acetyl-CoA molecules (see diagram below2).
A common question is why BHB is the go-to ketone body for exogenous ketone supplements. The likely reason is a combination of its efficient conversion into energy and its ease of formulation. In other words, that it is easier to formulate BHB into a nutritional supplement. And the body efficiently converts BHB to acetoacetic acid, which effectively raises blood ketone levels.
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.
Plenty of supplements make you a fractionally better sportsman and these are no different. The synthetic exogenous ketones helped Olympic-caliber cyclists cover an average of 411 additional meters during a 30-minute time-trial, which resulted in a two percent increase in overall speed, found a paper in Cell Metabolism. That can be the difference between feeling the glorious tug of the winner’s ribbon across your chest or rolling in with the stragglers.
If you’re somebody who isn’t already a keto-goer, then you might be wondering why? Why do I need to limit my carbohydrate intake to get my body into a state of ketosis? Simply put, and without getting to technical; you want your body to be in a constant state where fat is the is the primary source of fuel for the body rather than glucose. You see, once you eat carbs, the body will break this down into glucose which it will then use for fuel before tapping into your fat reserves for energy. If you limit the amount of glucose that is in your system by restricting your carbohydrate intake, the body has no choice but to tap into your fat stores for energy. Fats are metabolised in the liver where ketones are then produced for your physical and cognitive needs.
Because of how effectively exogenous ketones can reduce hunger for those in ketosis, pay attention to the cues your body gives you. It’s possible to extend your fasts longer than necessary because of a decreased appetite cue. While those who have some weight to lose might be tempted to think this is a favorable side effect, there is a difference between fasting and starving for nutrients. Make sure to get enough food to support your activities and maintain your muscle mass.
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.
The body will start making ketones when either we go extended periods without food, or we restrict the one dietary component that stops ketone formation – this being carbohydrates and also minimising protein intake as this also can halt ketone. In turn, your primary source of food is fat, with very little carbohydrate and a small amount of protein.”
Measurements taken included whole blood glucose and BHB (every 5 minutes); VO2 and VCO2 (every 15 seconds); HR (continuous); RQ is calculated as the ratio of VO2 and VCO2. In the video of this post I explain what VO2, VCO2, and RQ tell us about energy expenditure and substrate use—very quickly, RQ typically varies between about 0.7 and 1.0—the closer RQ is to 0.7, the more fat is being oxidized; the reverse is true as RQ approaches 1.0
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