Getting enough sleep not only helps in the production of growth hormones vital for muscle growth, but it plays a particular role as already discussed. If you’re intermittently fasting then sleep is crucial is helping you sustain the fast. 6-10 hours of your day will be dedicated to sleep, helping you to reboot and not think about food during this time. That means less time for you to actually be fasting! Stress is another factor – if we don’t get enough sleep, we’ll tend to feel more stress and agitation throughout the day. Ensuring that we’re well rested plays a huge part in keeping down cortisol levels so that are insulin and blood sugar levels don’t spike.
I’m not sure whether I am leto-adapted but have been following the keto program for about 6 weeks. The scale and the eye confirm I have been burning fat. I’ve been using ketostix to keep track of ketones as I don’t prefer to prick my fingers to get blood measurements. I have reached my weight loss goal and planning to transition to maintenance in the next couple of weeks. I’m curious if exogenous ketones will be aid in maintaining my weight.

The best time to start a one day fast is in the evening (neither morning nor the night) – preferably, around 6 pm. It won’t make you lose your vital energy during the daytime workouts, nor does it let you sleep with undigested foodstuff in your stomach. Taking late meals and sleeping with undigested food doesn’t allow your body to rest. So the natural healing mechanism of your body fails during the sleep time as the entire resources are busy digesting your food.
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.
Concentrations of plasma non-esterified fatty acids, triacylglycerol, glucose, and insulin following equimolar ketone ester and ketone salt drinks, at two amounts, in subjects (n = 15) at rest. Values are means ± SEM. (A) Plasma FFA. (B) Plasma TG. (C) Plasma glucose. (D) Plasma insulin at baseline and after 30 and 60 min. EH, ketone ester high; EL, ketone ester low; SH, ketone salt high; SL, ketone salt low. *p < 0.05 difference from baseline value.
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).
Second, there are inherent metabolic differences between boosting ketones via diet and boosting ketones via supplements. On a ketogenic diet, ketones go up because you’re converting body and dietary fat into ketone bodies. A rise in endogenous ketones means you’re burning fat and building the requisite machinery to metabolize the new energy source. On exogenous ketones, ketones go up because you ate some ketones; conversion of body and dietary fat into ketone bodies goes down if anything.
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.)

MCT oil has recently been used to induce nutritional ketosis although it produces dose-dependent gastrointestinal (GI) side effects in humans that limit the potential for its use to significantly elevate ketones (>0.5 mM). Despite these limitations, Azzam and colleagues published a case report in which a 43-year-old-man had a significant decrease in seizure frequency after supplementing his diet with 4 tablespoons of MCT oil twice daily [96]. An attempt to increase his dosage to 5 tablespoons twice daily was halted by severe GI intolerance. Henderson et al. observed that 20 % of patients reported GI side effects with a 20 g dose of ketogenic agent AC-1202 in a double blind trial in mild to moderate Alzheimer’s patients [24]. We visually observed similar gastrointestinal side effects (loose stools) in the rats treated with MCT oil in our study. Rats were closely monitored to avoid dehydration, and gastric motility returned to normal between 12–24 h. Interestingly, the BMS + MCT supplement elevated βHB similarly to MCT oil alone, without causing the adverse gastrointestinal effects seen in MCT-supplemented rats. However, this could be due to the fact in a 10 g/kg dose of BMS + MCT, only 5 g/kg is MCT alone, which is less than the 10 g/kg dose that elicits the GI side effects. This suggests that this novel combination may provide a more useful therapeutic option than MCT oil alone, which is limited in its ability to elevate ketones in humans.

Another important difference between endogenous and exogenous BOHB is that most synthetic BOHB used in dietary supplements is a mixture of the two ‘D’ and ‘L’ isomers, whereas endogenously produced BOHB consists of just the D-isomer. Metabolically, the two isomers are very different, and current published information indicates that most of the energy and signaling benefits of BOHB derive from the D-form. This is potentially problematic because the L-isomers are not metabolized via the same chemical pathways as the D-forms (Lincoln 1987, Stubbs 2017), and it remains unclear whether humans can convert the L-form to the D-form.

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).
Our mission at Ketologie is to help educate and assist people in transitioning to a ketogenic way of eating for life. Primarily, we support people achieving this via adopting a VLCHF or ketogenic way of eating. Exogenous ketones can however play a useful role in transitioning to and maintaining a ketogenic lifestyle, and so we have exhaustively researched and developed a unique, “next level” ketone supplement that focuses specifically on optimizing health via the gut-brain axis.

Caveat emptor: the following post doesn’t come close to answering most of these questions. I only document my experience with BHB salts (and a non-commercial version at that), but say little to nothing about my experience with BHB esters or AcAc esters. But it will provide you will some context and understanding about what exogenous ketones are, and what they might do for athletic performance. We’ll likely podcast about the questions and topics above and cover other aspects of exogenous ketones in more detail.

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Medical Disclaimer: The material on this site is provided for informational purposes only and is not medical advice. Always consult your physician before beginning any diet or exercise program.

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