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.
Most people confuse thirst for hunger, and it's crucial to not make that mistake when you're dieting. Try to drink water first before heading to the fridge to get some snacks--you might realize that you're not really hungry at all and you are, in fact, only thirsty. Training yourself to spot the difference between hunger and thirst will help you induce ketosis faster.
Exogenous ketones are also for those just looking to try it out. It lets anyone be able to access ketones simply by consuming these exogenous forms of ketones. Technically, MCTs are not an exogenous ketone such as BHB salts. They’re not ketones. But they readily convert into ketones. So MCT oils and powders are a great source of endogenous ketones. The end result is similar, and thus this top 5 list includes MCT oil powders as well as BHB salts.
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.
In fact this was one of the biggest surprises I had when exploring ketosis. For years I have been following a cyclical lower carb diet. For years I wouldn’t consume a carb until later in the afternoon (ala Carb Backloading style). After eating 5 days without any carbs I tested my ketone levels… they were 0.1 mmol. This reading was done first thing in the morning (10 hours fasted) after 5 days without a carb in my diet.
If you have already mastered the Very Low Carbohydrate (VLC) or ketogenic way of eating, and/or are eating at a caloric deficit, exercising or fasting you are naturally creating the optimal conditions for your body to produce ketones and put your body into nutritional ketosis. By strict adherence to a well-formulated ketogenic diet (complete with higher levels of mineral salts) you should be able to produce all the ketones you need naturally (endogenously). If you are new or inexperienced in ketogenic eating however; or if you or a family member struggles to adhere to a ketogenic diet, then supplementation with exogenous ketones may be very beneficial. Not only will ketone supplements help to mitigate hunger and carb cravings, but they will also help you stave off carb flu symptoms (see below), giving you the best possible chance of long-term success.
Participants consumed 13.2 mmol.kg−1 of βHB (6.6 mmol.kg−1 or 1,161 mg/kg of KE) over 9 h, either as 3 drinks of 4.4 mmol.kg−1 of βHB at 3 h intervals (n = 12), or as an initial bolus of 4.4 mmol.kg−1 of βHB given through a nasogastric tube, followed by an infusion of 1.1 mmol.kg.h−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.
EK use can be compared to the nootropics that have been developed for optimizing focus, memory creation, and faster cognitive performance. While you may not notice this effect on a minute to minute basis if you keep a journal of “forgetful moments” you’ll find that you have fewer of them as time goes on. You’ll also find that you’re able to come up with better ideas, and your workflow is more efficient through the day (10, 11).
An alternative to the ketogenic diet is consumption of drinks containing exogenous dietary ketones, such as ketone esters (KE) and ketone salts (KS). The metabolic effects of KS ingestion have been reported in rats (Ari et al., 2016; Kesl et al., 2016; Caminhotto et al., 2017), in three extremely ill pediatric patients (Plecko et al., 2002; Van Hove et al., 2003; Valayannopoulos et al., 2011) and in cyclists (O'Malley et al., 2017; Rodger et al., 2017). However, the concentrations of blood βHB reached were low (<1 mM) and a high amount of salt, consumed as sodium, potassium and/or calcium βHB, was required to achieve ketosis. Furthermore, dietary KS are often racemic mixtures of the two optical isoforms of βHB, d-βHB, and l-βHB, despite the metabolism of l-βHB being poorly understood (Webber and Edmond, 1977; Scofield et al., 1982; Lincoln et al., 1987; Desrochers et al., 1992). The pharmacokinetics and pharmacodynamics of KS ingestion in healthy humans at rest have not been reported.
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.
The difference in peak blood d-βHB concentrations between matched amounts of βHB as ester or salts arose because the salt contained l-βHB, as the blood concentrations of d- plus l-βHB isoforms were similar for both compounds. It is unclear if kinetic parameters of KE and KS drinks would be similar if matched d-βHB were taken in the drinks. Unlike d-βHB, blood l-βHB remained elevated for at least 8 h following the drink, suggesting an overall lower rate of metabolism of l-βHB as urinary elimination of l-βHB was in proportion to plasma concentration. Despite similar concentrations of total βHB, breath acetone was ~50% lower following KS drinks compared to KE, suggesting fundamental differences in the metabolic fates of D- and L-βHB. These findings support both previous hypotheses (Veech and King, 2016) and experimental work in rats (Webber and Edmond, 1977), which suggested that the l-isoform was less readily oxidized than the d-isoform, and is processed via different pathways, perhaps in different cellular compartments. It seems that l-βHB is not a major oxidative fuel at rest, and may accumulate with repeated KS drinks. However, the putative signaling role of l-βHB in humans remains unclear. In rodent cardiomyocytes, l-βHB acts as a signal that modulates the metabolism of d-βHB and glucose, Tsai et al. (2006) although no differences in blood glucose were seen here. Furthermore, L-βHB can act as a cellular antioxidant, although to a lesser extent than D-βHB (Haces et al., 2008).
Also, this experiement should be of interest. Two men followed a ‘traditional Eskimo’ diet for 1 year. After the year eating a low carb high fat diet, it was found that the men had a diminished tolerance to carbohydrates, something that did not occur in Eskimos eating the same diet. It took the mean nearly a month of eating a ‘normal diet’ before their glucose tolerance returned to baseline.
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.
Exogenous ketones cause the body to rely less on fat as fuel (see Fig 3). Fat takes longer to metabolise for energy than muscle glycogen. This is why fatty acids are not the preferred fuel under heavy exercise. This could be useful for keto-adapted athletes performing high-intensity cardiovascular or strength training.12 This is particularly useful for the Keto-adapted athlete who wants to undergo high-intensity cardiovascular or strength training.
There is one viable explanation for consuming ketones. If you're in a calorie or carb-restricted state, then maybe during a workout it would make sense. But even then, that really only applies to endurance activities, since it has more to do with enhancing aerobic performance (where oxygen is required), than it does with enhancing high-intensity efforts (where it's not).
The table below shows the same measurements and calculations as the above table, but under the test conditions. You’ll note that BHB is higher at the start and falls more rapidly, as does glucose (for reasons I’ll explain below). HR data are almost identical to the control test, but VO2 and VCO2 are both lower. RQ, however, is slightly higher, implying that the reduction in oxygen consumption was greater than the reduction in carbon dioxide production.
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