Acute nutritional ketosis: implications for exercise performance and metabolism

Effect of acute ingestion of β-hydroxybutyrate salts on the response to graded exercise in trained cyclists

Acute ingestion of ketone salts induces nutritional ketosis by elevating β-hydroxybutyrate (βHB), but few studies have examined the metabolic effects of ingestion prior to exercise. Nineteen trained cyclists (12 male, 7 female) undertook graded exercise (8 min each at ∼30%, 40%, 50%, 60%, 70%, and 80% VO_2peak) on a cycle ergometer on two occasions separated by either 7 or 14 days. Trials included ingestion of boluses of either (i) plain water (3.8 mL kg body mass^-1) (CON) or (ii) βHB salts (0.38 g kg body mass^-1) in plain water (3.8 mL kg body mass^-1) (KET), at both 60 min and 15 min prior to exercise. During KET, plasma [βHB] increased to 0.33 ± 0.16 mM prior to exercise and 0.44 ± 0.15 mM at the end of exercise (both p < .05). Plasma glucose was 0.44 ± 0.27 mM lower (p < .01) 30 min after ingestion of KET and remained ∼0.2 mM lower throughout exercise compared to CON (p < .001). Respiratory exchange ratio (RER) was higher during KET compared to CON (p < .001) and 0.03-0.04 higher from 30%VO_2peak to 60%VO_2peak (all p < .05). No differences in plasma lactate, rate of perceived exertion, or gross or delta efficiency were observed between trials. Gastrointestinal symptoms were reported in 13 out of 19 participants during KET. Acute ingestion of βHB salts induces nutritional ketosis and alters the metabolic response to exercise in trained cyclists. Elevated RER during KET may be indicative of increased ketone body oxidation during exercise, but at the plasma βHB concentrations achieved, ingestion of βHB salts does not affect lactate appearance, perceived exertion, or muscular efficiency.

Nutritional ketone salts increase fat oxidation but impair high-intensity exercise performance in healthy adult males

This study investigated the impact of raising plasma beta-hydroxybutyrate (β-OHB) through ingestion of ketone salts on substrate oxidation and performance during cycling exercise. Ten healthy adult males (age, 23 ± 3 years; body mass index, 25 ± 3 kg/m2, peak oxygen uptake, 45 ± 10 mL/(kg·min)−1) were recruited to complete 2 experimental trials. Before enrollment in the experimental conditions, baseline anthropometrics and cardiorespiratory fitness (peak oxygen uptake) were assessed and familiarization to the study protocol was provided. On experimental days, participants reported to the laboratory in the fasted state and consumed either 0.3 g/kg β-OHB ketone salts or a flavour-matched placebo at 30 min prior to engaging in cycling exercise. Subjects completed steady-state exercise at 30%, 60%, and 90% ventilatory threshold (VT) followed by a 150-kJ cycling time-trial. Respiratory exchange ratio (RER) and total substrate oxidation were derived from indirect calorimetry. Plasma glucose, lactate, and ketones were measured at baseline, 30 min post-supplement, post–steady-state exercise, and immediately following the time-trial. Plasma β-OHB was elevated from baseline and throughout the entire protocol in the ketone condition (p < 0.05). RER was lower at 30% and 60% VT in the ketone compared with control condition. Total fat oxidation was greater in the ketone versus control (p = 0.05). Average time-trial power output was ∼7% lower (–16 W, p = 0.029) in the ketone condition. Ingestion of ketone salts prior to exercise increases fat oxidation during steady-state exercise but impairs high-intensity exercise performance.

The Effect of a 12-Week Beta-hydroxy-beta-methylbutyrate (HMB) Supplementation on Highly-Trained Combat Sports Athletes: A Randomised, Double-Blind, Placebo-Controlled Crossover Study

The aim of this study was to verify the effect of beta-hydroxy-beta-methylbutyrate (HMB) supplementation on physical capacity, body composition and the value of biochemical parameters in highly-trained combat sports athletes. Forty-two males highly-trained in combat sports were subjected to 12 weeks of supplementation with HMB and a placebo in a randomized, placebo controlled, double-blind crossover manner. Over the course of the experiment, aerobic and anaerobic capacity was determined, while analyses were conducted on body composition and levels of creatine kinase, lactate dehydrogenase, testosterone, cortisol and lactate. Following HMB supplementation, fat-free mass increased (p = 0.049) with a simultaneous reduction of fat mass (p = 0.016) in comparison to placebo. In turn, after HMB supplementation, the following indicators increased significantly in comparison to the placebo: the time to reach ventilatory threshold (p < 0.0001), threshold load (p = 0.017) and the threshold HR (p < 0.0001), as well as anaerobic peak power (p = 0.005), average power (p = 0.029), maximum speed (p < 0.001) and post-exercise lactate concentrations (p < 0.0001). However, when compared to the placebo, no differences were observed in blood marker levels. The results indicate that supplying HMB promotes advantageous changes in body composition and stimulates an increase in aerobic and anaerobic capacity in combat sports athletes.

Intake of a Ketone Ester Drink during Recovery from Exercise Promotes mTORC1 Signaling but Not Glycogen Resynthesis in Human Muscle

Purpose: Ketone bodies are energy substrates produced by the liver during prolonged fasting or low-carbohydrate diet. The ingestion of a ketone ester (KE) rapidly increases blood ketone levels independent of nutritional status. KE has recently been shown to improve exercise performance, but whether it can also promote post-exercise muscle protein or glycogen synthesis is unknown. Methods: Eight healthy trained males participated in a randomized double-blind placebo-controlled crossover study. In each session, subjects undertook a bout of intense one-leg glycogen-depleting exercise followed by a 5-h recovery period during which they ingested a protein/carbohydrate mixture. Additionally, subjects ingested a ketone ester (KE) or an isocaloric placebo (PL). Results: KE intake did not affect muscle glycogen resynthesis, but more rapidly lowered post-exercise AMPK phosphorylation and resulted in higher mTORC1 activation, as evidenced by the higher phosphorylation of its main downstream targets S6K1 and 4E-BP1. As enhanced mTORC1 activation following KE suggests higher protein synthesis rates, we used myogenic C₂C₁₂ cells to further confirm that ketone bodies increase both leucine-mediated mTORC1 activation and protein synthesis in muscle cells. Conclusion: Our results indicate that adding KE to a standard post-exercise recovery beverage enhances the post-exercise activation of mTORC1 but does not affect muscle glycogen resynthesis in young healthy volunteers. In vitro, we confirmed that ketone bodies potentiate the increase in mTORC1 activation and protein synthesis in leucine-stimulated myotubes. Whether, chronic oral KE intake during recovery from exercise can facilitate training-induced muscular adaptation and remodeling need to be further investigated.

Metabolism of ketone bodies during exercise and training: physiological basis for exogenous supplementation

Optimising training and performance through nutrition strategies is central to supporting elite sportspeople, much of which has focused on manipulating the relative intake of carbohydrate and fat and their contributions as fuels for energy provision. The ketone bodies, namely acetoacetate, acetone and β-hydroxybutyrate (βHB), are produced in the liver during conditions of reduced carbohydrate availability and serve as an alternative fuel source for peripheral tissues including brain, heart and skeletal muscle. Ketone bodies are oxidised as a fuel source during exercise, are markedly elevated during the post-exercise recovery period, and the ability to utilise ketone bodies is higher in exercise-trained skeletal muscle. The metabolic actions of ketone bodies can alter fuel selection through attenuating glucose utilisation in peripheral tissues, anti-lipolytic effects on adipose tissue, and attenuation of proteolysis in skeletal muscle. Moreover, ketone bodies can act as signalling metabolites, with βHB acting as an inhibitor of histone deacetylases, an important regulator of the adaptive response to exercise in skeletal muscle. Recent development of ketone esters facilitates acute ingestion of βHB that results in nutritional ketosis without necessitating restrictive dietary practices. Initial reports suggest this strategy alters the metabolic response to exercise and improves exercise performance, while other lines of evidence suggest roles in recovery from exercise. The present review focuses on the physiology of ketone bodies during and after exercise and in response to training, with specific interest in exploring the physiological basis for exogenous ketone supplementation and potential benefits for performance and recovery in athletes.

Oral β-hydroxybutyrate increases ketonemia, decreases visceral adipocyte volume and improves serum lipid profile in Wistar rats

Background

Ketosis can be induced in humans and in animals by fasting or dietary interventions, such as ketogenic diets. However, the increasing interest on the ketogenic state has motivated the development of alternative approaches to rapidly increase ketonemia using less drastic interventions. Here, it was tested whether oral intake of a β-hydroxybutyrate (βHB) mineral salt mixture could increase ketonemia in Wistar rats without any other dietary changes, thereby being a useful model to study ketones effects alone on metabolism.

Methods

βHB salts were orally administered to provoke elevation in the ketonemia. Effects of this intervention were tested acutely (by gavage) and chronically (4 weeks in drinking water). Acutely, a concomitant glucose overload was used to suppress endogenous ketogenesis and verify whether βHB salts were really absorbed or not. Long-term administration allowed to weekly evaluate the impact on ketonemia, blood glucose and, after 4 weeks, on body weight, visceral fat mass, lipid blood profile, serum lipolysis products and adiponectinemia.

Results

βHB salts increased ketonemia in acute and long-term administrations, improved blood lipid profile by raising HDL-cholesterol concentration and decreasing LDL/HDL ratio, while reduced visceral adipocyte volume. Mean ketonemia correlated positively with HDLc and negatively with adipocyte volume and serum lipolysis products.

Conclusions

Oral βHB can rapidly increase ketonemia and, therefore, be used as an acute and long-term animal model of ketosis. Long-term treatment points to important beneficial effects of ketone bodies in serum lipid concentrations and visceral fat mass. These results may help to explain the metabolic adaptations following ketogenic diets, such as a better body fat control and a serum lipid profile improvement.

Evidence that supports the prescription of low-carbohydrate high-fat diets: a narrative review

Low-carbohydrate high-fat (LCHF) diets are a highly contentious current topic in nutrition. This narrative review aims to provide clinicians with a broad overview of the effects of LCHF diets on body weight, glycaemic control and cardiovascular risk factors while addressing some common concerns and misconceptions. Blood total cholesterol and LDL-cholesterol concentrations show a variable, highly individual response to LCHF diets, and should be monitored in patients adhering to this diet. In contrast, available evidence from clinical and preclinical studies indicates that LCHF diets consistently improve all other markers of cardiovascular risk-lowering elevated blood glucose, insulin, triglyceride, ApoB and saturated fat (especially palmitoleic acid) concentrations, reducing small dense LDL particle numbers, glycated haemoglobin (HbA_1c) levels, blood pressure and body weight while increasing low HDL-cholesterol concentrations and reversing non-alcoholic fatty liver disease (NAFLD). This particular combination of favourable modifications to all these risk factors is a benefit unique to LCHF diets. These effects are likely due in part to reduced hunger and decreased ad libitum calorie intake common to low-carbohydrate diets, allied to a reduction in hyperinsulinaemia, and reversal of NAFLD. Although LCHF diets may not be suitable for everyone, available evidence shows this eating plan to be a safe and efficacious dietary option to be considered. LCHF diets may also be particularly beneficial in patients with atherogenic dyslipidaemia, insulin resistance, and the frequently associated NAFLD.

Novel ketone diet enhances physical and cognitive performance

Ketone bodies are the most energy-efficient fuel and yield more ATP per mole of substrate than pyruvate and increase the free energy released from ATP hydrolysis. Elevation of circulating ketones via high-fat, low-carbohydrate diets has been used for the treatment of drug-refractory epilepsy and for neurodegenerative diseases, such as Parkinson's disease. Ketones may also be beneficial for muscle and brain in times of stress, such as endurance exercise. The challenge has been to raise circulating ketone levels by using a palatable diet without altering lipid levels. We found that blood ketone levels can be increased and cholesterol and triglycerides decreased by feeding rats a novel ketone ester diet: chow that is supplemented with (R)-3-hydroxybutyl (R)-3-hydroxybutyrate as 30% of calories. For 5 d, rats on the ketone diet ran 32% further on a treadmill than did control rats that ate an isocaloric diet that was supplemented with either corn starch or palm oil (P < 0.05). Ketone-fed rats completed an 8-arm radial maze test 38% faster than did those on the other diets, making more correct decisions before making a mistake (P < 0.05). Isolated, perfused hearts from rats that were fed the ketone diet had greater free energy available from ATP hydrolysis during increased work than did hearts from rats on the other diets as shown by using [31P]-NMR spectroscopy. The novel ketone diet, therefore, improved physical performance and cognitive function in rats, and its energy-sparing properties suggest that it may help to treat a range of human conditions with metabolic abnormalities.-Murray, A. J., Knight, N. S., Cole, M. A., Cochlin, L. E., Carter, E., Tchabanenko, K., Pichulik, T., Gulston, M. K., Atherton, H. J., Schroeder, M. A., Deacon, R. M. J., Kashiwaya, Y., King, M. T., Pawlosky, R., Rawlins, J. N. P., Tyler, D. J., Griffin, J. L., Robertson, J., Veech, R. L., Clarke, K. Novel ketone diet enhances physical and cognitive performance.

Fuel for the work required: a practical approach to amalgamating train-low paradigms for endurance athletes

Using an amalgamation of previously studied "train-low" paradigms, we tested the effects of reduced carbohydrate (CHO) but high leucine availability on cell-signaling responses associated with exercise-induced regulation of mitochondrial biogenesis and muscle protein synthesis (MPS). In a repeated-measures crossover design, 11 males completed an exhaustive cycling protocol with high CHO availability before, during, and after exercise (HIGH) or alternatively, low CHO but high protein (leucine enriched) availability (LOW + LEU). Muscle glycogen was different (P < 0.05) pre-exercise (HIGH: 583 ± 158, LOW + LEU: 271 ± 85 mmol kg(-1) dw) but decreased (P < 0.05) to comparable levels at exhaustion (≈100 mmol kg(-1) dw). Despite differences (P < 0.05) in exercise capacity (HIGH: 158 ± 29, LOW + LEU: 100 ± 17 min), exercise induced (P < 0.05) comparable AMPKα2 (3-4-fold) activity, PGC-1α (13-fold), p53 (2-fold), Tfam (1.5-fold), SIRT1 (1.5-fold), Atrogin 1 (2-fold), and MuRF1 (5-fold) gene expression at 3 h post-exercise. Exhaustive exercise suppressed p70S6K activity to comparable levels immediately post-exercise (≈20 fmol min(-1) mg(-1)). Despite elevated leucine availability post-exercise, p70S6K activity remained suppressed (P < 0.05) 3 h post-exercise in LOW + LEU (28 ± 14 fmol min(-1) mg(-1)), whereas muscle glycogen resynthesis (40 mmol kg(-1) dw h(-1)) was associated with elevated (P < 0.05) p70S6K activity in HIGH (53 ± 30 fmol min(-1) mg(-1)). We conclude: (1) CHO restriction before and during exercise induces "work-efficient" mitochondrial-related cell signaling but; (2) post-exercise CHO and energy restriction maintains p70S6K activity at basal levels despite feeding leucine-enriched protein. Our data support the practical concept of "fuelling for the work required" as a potential strategy for which to amalgamate train-low paradigms into periodized training programs.

Nutritional Ketosis Alters Fuel Preference and Thereby Endurance Performance in Athletes

Ketosis, the metabolic response to energy crisis, is a mechanism to sustain life by altering oxidative fuel selection. Often overlooked for its metabolic potential, ketosis is poorly understood outside of starvation or diabetic crisis. Thus, we studied the biochemical advantages of ketosis in humans using a ketone ester-based form of nutrition without the unwanted milieu of endogenous ketone body production by caloric or carbohydrate restriction. In five separate studies of 39 high-performance athletes, we show how this unique metabolic state improves physical endurance by altering fuel competition for oxidative respiration. Ketosis decreased muscle glycolysis and plasma lactate concentrations, while providing an alternative substrate for oxidative phosphorylation. Ketosis increased intramuscular triacylglycerol oxidation during exercise, even in the presence of normal muscle glycogen, co-ingested carbohydrate and elevated insulin. These findings may hold clues to greater human potential and a better understanding of fuel metabolism in health and disease.

The Population Pharmacokinetics of D-β-hydroxybutyrate Following Administration of (R)-3-Hydroxybutyl (R)-3-Hydroxybutyrate

The administration of ketones to induce a mild ketosis is of interest for the alleviation of symptoms associated with various neurological disorders. This study aimed to understand the pharmacokinetics (PK) of D-β-hydroxybutyrate (BHB) and quantify the sources of variability following a dose of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate (ketone monoester). Healthy volunteers (n = 37) were given a single drink of the ketone monoester, following which, 833 blood BHB concentrations were measured. Two formulations and five dose levels of ketone monoester were used. A nonlinear mixed effect modelling approach was used to develop a population PK model. A one compartment disposition model with negative feedback effect on endogenous BHB production provided the best description of the data. Absorption was best described by two consecutive first-order inputs and elimination by dual processes involving first-order (CL = 10.9 L/h) and capacity limited elimination (V max = 4520 mg/h). Covariates identified were formulation (on relative oral bioavailable fraction and absorption rate constant) and dose (on relative oral bioavailable fraction). Lean body weight (on first-order clearance) and sex (on apparent volume of distribution) were also significant covariates. The PK of BHB is complicated by complex absorption process, endogenous production and nonlinear elimination. Formulation and dose appear to strongly influence the kinetic profile following ketone monoester administration. Further work is needed to quantify mechanisms of absorption and elimination of ketones for therapeutic use in the form of ketone monoester.