A Ketone Ester Drink Lowers Human Ghrelin and Appetite

Perceptions of appetite do not match hormonal measures of appetite in trained competitive cyclists and triathletes following a ketogenic diet compared to a high-carbohydrate or habitual diet: A randomized crossover trial

Endurance athletes may implement rigid dietary strategies, such as the ketogenic diet (KD), to improve performance. The effect of the KD on appetite remains unclear in endurance athletes. This study analyzed the effects of a KD, a high-carbohydrate diet (HCD), and habitual diet (HD) on objective and subjective measures of appetite in trained cyclists and triathletes, and hypothesized that the KD would result in greater objective and subjective appetite suppression. Six participants consumed the KD and HCD for 2-weeks each, in a random order, following their HD. Fasting appetite measures were collected after 2-weeks on each diet. Postprandial appetite measures were collected following consumption of a ketogenic meal after the KD, high-carbohydrate meal after the HCD, and standard American/Western meal after the HD. Fasting total ghrelin (GHR) was lower and glucagon-like peptide-1 (GLP-1) and hunger were higher following the KD versus HD and HCD. Fasting insulin was not different. Mixed-effects model repeated measures analysis and effect sizes and 95% confidence intervals showed that postprandial GHR and insulin were lower and GLP-1 was higher following the ketogenic versus the standard and high-carbohydrate meals. Postprandial appetite ratings were not different across test meals. In conclusion, both fasting and postprandial concentrations of GHR were lower and GLP-1 were higher following the KD than the HC and HD, and postprandial insulin was lower on the KD. Subjective ratings of appetite did not correspond with the objective measures of appetite in trained competitive endurance athlete. More research is needed to confirm our findings.

Produced β-hydroxybutyrate after β-hydroxy-β-methylbutyrate (HMB) administration may contribute HMB function in mice

β-Hydroxy-β-methylbutyrate (HMB) is an intermediate in the metabolism of the branched-chain amino acid leucine. HMB has several demonstrated effects on skeletal muscle function, some of which are contradictory. In addition, the effect of exogenous HMB intake on the levels of intermediate metabolites is not known. Therefore, we investigated changes in HMB metabolites after oral HMB administration in mice. First, ICR mice were treated with either distilled water or HMB (0.215 g/10 mL/kg). Sampling was performed at 0, 1, 6, 12, and 24 h after administration. Next, ICR mice were given distilled water or HMB (0.215 g/10 mL/kg/d) for 10 d. Mice given HMB shown a significant increase in liver β-methylcrotonyl-CoA and increased β-hydroxybutyrate in plasma and the gastrocnemius muscle 1 h after HMB administration. Mice administered HMB for 10 d showed significantly decreased food intake and body weight; however, the relative weight of the gastrocnemius muscle was significantly increased. These results may be attributed to an increase in β-hydroxybutyrate resulting from exogenous HMB, since β-hydroxybutyrate inhibits food intake and suppresses skeletal muscle catabolism. In conclusion, β-hydroxybutyrate, a metabolite of HMB, was found to play an important role in the function of HMB.

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β-Hydroxybutyrate levels in plasma and gastrocnemius were enhanced by HMB.

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HMB increases in tissues and plasma returned to original levels within 6 h.

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HMB treatment for 10 d suppressed food intake and decreased body weight.

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Gastrocnemius weight was increased despite deceased body weight in HMB-treated mice.

The protective effect of beta-hydroxybutyric acid on renal glomerular epithelial cells in adriamycin-induced injury

Beta-hydroxybutyric acid (BHB) exerts a protective effect in experimental of kidney disease models. However, the mechanisms underlying this activity are not well defined. BHB stands out for its ability to inhibit the Nε-lysine acetylation of histone and non-histone proteins, which may affect cellular processes and protein functions. In adriamycin-injured murine glomerular podocytes, BHB ameliorates podocyte damage and preserves actin cytoskeleton integrity, reminiscent of the effect of MS275, a highly selective inhibitor of lysine deacetylase. Further research found that adriamycin causes the reduced acetylation of nephrin, WT-1, and GSK3β. This process is abrogated by the lysine deacetylase inhibitor or BHB, suggesting that the acetylation of these molecules regulates their activity. In contrast, anacardic acid, a selective inhibitor of acetyltransferase, decreases the acetylation of nephrin, WT-1, and GSK3β and mitigates the podocyte protective effects of BHB. Taken together, BHB attenuates adriamycin-elicited glomerular epithelial cell injury, at least in part, by inhibiting the deacetylation of the key molecules implicated in glomerular injury.

Acute ketosis inhibits appetite and decreases plasma concentrations of acyl ghrelin in healthy young men

AIM

To investigate the acute effect of ketone ester (KE) ingestion on appetite and plasma concentrations of acyl ghrelin (AG), unacylated ghrelin (UAG) and glucagon-like peptide-1 (GLP-1) secretion, and to compare responses with those elicited by isocaloric glucose (GLU) administration.

METHODS

We examined 10 healthy young men on three separate occasions using a placebo (PBO)-controlled crossover design. A KE versus taste-matched isovolumetric and isocaloric 50% GLU and taste-matched isovolumetric PBO vehicle was orally administered. Our main outcome measures were plasma concentrations of AG, UAG, glucose-dependent insulinotropic polypeptide (GIP) and GLP-1 along with appetite sensation scores assessed by visual analogue scale.

RESULTS

KE ingestion resulted in an average peak beta-hydroxybutyrate concentration of 5.5 mM. AG and UAG were lowered by approximately 25% following both KE and GLU intake compared with PBO. In the case of AG, the differences were -52.1 (-79.4, -24.8) for KE and -48.4 (-75.4, -21.5) pg/mL for GLU intake (P < .01). Concentrations of AG remained lower with KE but returned to baseline and were comparable with PBO levels after GLU intake. GLP-1, GIP, gastrin and cholecystokinin were not affected by KE ingestion.

CONCLUSION

Our results suggest that the suppressive effects on appetite sensation scores associated with hyperketonaemia are more probable to be mediated through reduced ghrelin concentrations than by increased activity of cholecystokinin, gastrin, GIP or GLP-1.

Ketogenic diets and appetite regulation

PURPOSE OF REVIEW

The popularity of ketogenic diets in the treatment of obesity has increased dramatically over the last years, namely due to their potential appetite suppressant effect. The purpose of this review was to examine the latest evidence regarding the impact of ketogenic diets on appetite.

RECENT FINDINGS

The majority of the studies published over the last 2 years adds to previous evidence and shows that ketogenic diets suppress the increase in the secretion of the hunger hormone ghrelin and in feelings of hunger, otherwise see when weight loss is induced by non-ketogenic diets. Research done using exogenous ketones point out in the same direction. Even though the exact mechanisms by which ketogenic diets suppress appetite remain to be fully determined, studies show that the more ketotic participants are (measured as β-hydroxybutyrate plasma concentration), the smaller is the increase in ghrelin and hunger and the larger is the increase in the release of satiety peptides. Further evidence for a direct effect of ketones on appetite comes from studies using exogenous ketones.

SUMMARY

The appetite suppressant effect of ketogenic diets may be an important asset for improving adherence to energy restricted diets and weight loss outcomes.

The role of age in the physiological adaptations and psychological responses in bikini-physique competitor contest preparation: a case series

The increased popularity of the bikini-physique competitions has not translated to greater research identifying the influence of age on adaptations during contest preparation. The purpose of this case series was to observe how age may influence the adaptations normally seen during preparation and the exploration of newer protocols to address adaptations more relative to the judging standards. Over a 16-week pre-contest preparation, a 32-y bikini competitor (BC) and 44-y master's bikini competitor (MBC) visited the laboratory bi-weekly to observe changes in body fat mass (BF), lean body mass (LBM), bone mineral density (BMD), total body water (TBW); exploratory measures of deltoid cross-sectional area (DeltCSA), gluteus maximus muscle thickness (GMMT), and subcutaneous adipose tissue thickness (SAT); reproductive hormones estradiol (E2), luteinizing hormone (LH), and energy balance hormones triiodothyronine (T3), leptin and ghrelin; hydration status during contest preparation and the week of competition; resting metabolic rate (RMR); psychometric data related to perceived anxiety, stress, and body image were assessed. No differences between BC and MBC were observed in BF, LBM, BMD, and TBW. Both competitors showed a small loss in LBM. Both BC and MBC showed a contrasting increase in DeltCSA and a loss in GMMT. MBC showed to be slightly more dehydrated (1.025 vs 1.021 g·mL- 1) than BC. Both competitors maintained a euhydration status the day of the competition. No time differences were found between BC and MBC during RMR. BC showed a higher mean difference RMR compared to MBC (2.66 ± 0.75 kcal·kgLBM- 1·d- 1). MBC showed a higher mean difference in LH concentration (84.6 ± 6.01 IU·L- 1), which may be explained by perimenopausal status. MBC had a higher mean difference concentration of leptin (2.51 ± 0.24 ng·mL- 1·kgFM- 1), which was unperturbed by fat loss may be interrelated LH. BC self-reported a higher mean energy intake (15.07 ± 3.43 kcal·kgLBM- 1·d- 1) and higher aerobic training volume (93.26 ± 40.68 min·d). BC and MBC showed similar composition changes, slightly differing metabolic rates, and differing hormonal LH and leptin responses. This finding is in contrast to previous work showing both LH inhibition and leptin diurnal disturbance in younger, female athletes with low energy availability. The exploratory measures may have some benefit for bikini-physique competitors related to the judging criteria. Age did not seem to play a role in contest preparation adaptations.

Exogenous ketosis in patients with type 2 diabetes: Safety, tolerability and effect on glycaemic control

Introduction

Ketogenic diets have shown to improve glycaemic control in patients with type 2 diabetes. This study investigated the safety, tolerability, and effects on glycaemic control in patients with type 2 diabetes of an exogenous ketone monoester (KE) capable of inducing fasting‐like elevations in serum β‐hydroxybutyrate (βHB) without the need for caloric or carbohydrate restriction.

Methods

Twenty one participants (14 men and 7 women, aged 45 ± 11 years) with insulin‐independent type 2 diabetes, and unchanged hypoglycaemic medication for the previous 6 months, were recruited for this non‐randomised interventional study. Participants wore intermittent scanning glucose monitors (IS‐GM) for a total of 6 weeks and were given 25 ml of KE 3 times daily for 4 weeks. Serum electrolytes, acid‐base status, and βHB concentrations were measured weekly and cardiovascular risk markers were measured before and after the intervention. The primary endpoints were safety and tolerability, with the secondary endpoint being glycaemic control.

Results

The 21 participants consumed a total of 1,588 drinks (39.7 litres) of KE over the course of the intervention. Adverse reactions were mild and infrequent, including mild nausea, headache, and gastric discomfort following fewer than 0.5% of the drinks. Serum electrolyte concentrations, acid‐base status, and renal function remained normal throughout the study. Compared to baseline, exogenous ketosis induced a significant decrease in all glycaemic control markers, including fructosamine (335 ± 60 μmol/L to 290 ± 49 μmol/L, p < .01), HbA1c (61 ± 10 mmol/mol to 55 ± 9 mmol/mol [7.7 ± 0.9% to 7.2 ± 0.9%], p < .01), mean daily glucose (7.8 ± 1.4 mM to 7.4 ± 1.3 mM [140 ± 23 mg/dl to 133 ± 25 mg/dl], p < .01) and time in range (67 ± 11% to 69 ± 10%, p < .01).

Conclusions

Constant ketone monoester consumption over 1 month was safe, well tolerated, and improved glycaemic control in patients with type 2 diabetes.

This study involved a month of closely supervised exogenous ketosis using a ketone monoester. Additionally, it involved six weeks of continuous glucose monitorization to compare glucose control before, during and after exogenous ketosis. Exogenous ketosis was safe, well‐tolerated and improved glucose control.

Effects of Calorie Restriction on Health Span and Insulin Resistance: Classic Calorie Restriction Diet vs. Ketosis-Inducing Diet

As the incidence of Chronic Non-Communicable Diseases (CNCDs) increases, preventive approaches become more crucial. In this review, calorie restriction (CR) effects on human beings were evaluated, comparing the benefits and risks of different CR diets: classic CR vs. ketosis-inducing diets, including intermittent fasting (IF), classic ketogenic diet (CKD), fasting mimicking diet (FMD), very-low-calorie ketogenic Diet (VLCKD) and Spanish ketogenic Mediterranean diet (SKMD). Special emphasis on insulin resistance (IR) was placed, as it mediates metabolic syndrome (MS), a known risk factor for CNCD, and is predictive of MS diagnosis. CR is the most robust intervention known to increase lifespan and health span, with high evidence and known biochemical mechanisms. CR improves cardiometabolic risk parameters, boosts exercise insulin sensitivity response, and there may be benefits of implementing moderate CR on healthy young and middle-aged individuals. However, there is insufficient evidence to support long-term CR. CKD is effective for weight and MS management, and may have additional benefits such as prevention of muscle loss and appetite control. SKMD has extreme significance benefits for all the metabolic parameters studied. Studies show inconsistent benefits of IF compared to classic CR. More studies are required to study biochemical parameters, reinforce evidence, identify risks, and seek effective and safe nutritional CR approaches.

Acetyl-CoA Metabolism and Histone Acetylation in the Regulation of Aging and Lifespan

Acetyl-CoA is a metabolite at the crossroads of central metabolism and the substrate of histone acetyltransferases regulating gene expression. In many tissues fasting or lifespan extending calorie restriction (CR) decreases glucose-derived metabolic flux through ATP-citrate lyase (ACLY) to reduce cytoplasmic acetyl-CoA levels to decrease activity of the p300 histone acetyltransferase (HAT) stimulating pro-longevity autophagy. Because of this, compounds that decrease cytoplasmic acetyl-CoA have been described as CR mimetics. But few authors have highlighted the potential longevity promoting roles of nuclear acetyl-CoA. For example, increasing nuclear acetyl-CoA levels increases histone acetylation and administration of class I histone deacetylase (HDAC) inhibitors increases longevity through increased histone acetylation. Therefore, increased nuclear acetyl-CoA likely plays an important role in promoting longevity. Although cytoplasmic acetyl-CoA synthetase 2 (ACSS2) promotes aging by decreasing autophagy in some peripheral tissues, increased glial AMPK activity or neuronal differentiation can stimulate ACSS2 nuclear translocation and chromatin association. ACSS2 nuclear translocation can result in increased activity of CREB binding protein (CBP), p300/CBP-associated factor (PCAF), and other HATs to increase histone acetylation on the promoter of neuroprotective genes including transcription factor EB (TFEB) target genes resulting in increased lysosomal biogenesis and autophagy. Much of what is known regarding acetyl-CoA metabolism and aging has come from pioneering studies with yeast, fruit flies, and nematodes. These studies have identified evolutionary conserved roles for histone acetylation in promoting longevity. Future studies should focus on the role of nuclear acetyl-CoA and histone acetylation in the control of hypothalamic inflammation, an important driver of organismal aging.

Acute Nutritional Ketosis and Its Implications for Plasma Glucose and Glucoregulatory Peptides in Adults with Prediabetes: A Crossover Placebo-Controlled Randomized Trial

BACKGROUND

The potential of a ketone monoester (β-hydroxybutyrate; KEβHB) supplement to rapidly mimic a state of nutritional ketosis offers a new therapeutic possibility for diabetes prevention and management. While KEβHB supplementation has a glucose-lowering effect in adults with obesity, its impact on glucose control in other insulin-resistant states is unknown.

OBJECTIVES

The primary objective was to investigate the effect of KEβHB-supplemented drink on plasma glucose in adults with prediabetes. The secondary objective was to determine its impact on plasma glucoregulatory peptides.

METHODS

This randomized controlled trial [called CETUS (Cross-over randomizEd Trial of β-hydroxybUtyrate in prediabeteS)] included 18 adults [67% men, mean age = 55 y, mean BMI (kg/m2) = 28.4] with prediabetes (glycated hemoglobin between 5.7% and 6.4% and/or fasting plasma glucose between 100 and 125 mg/dL). Participants were randomly assigned to receive KEβHB-supplemented and placebo drinks in a crossover sequence (washout period of 7-10 d between the drinks). Blood samples were collected from 0 to 150 min, at intervals of 30 min. Paired-samples t tests were used to investigate the change in the outcome variables [β-hydroxybutyrate (βHB), glucose, and glucoregulatory peptides] after both drinks. Repeated measures analyses were conducted to determine the change in concentrations of the prespecified outcomes over time.

RESULTS

Blood βHB concentrations increased to 3.5 mmol/L within 30 minutes after KEβHB supplementation. Plasma glucose AUC was significantly lower after KEβHB supplementation than after the placebo [mean difference (95% CI): -59 (-85.3, -32.3) mmol/L × min]. Compared with the placebo, KEβHB supplementation led to significantly greater AUCs for plasma insulin [0.237 (0.044, 0.429) nmol/L × min], C-peptide [0.259 (0.114, 0.403) nmol/L × min], and glucose-dependent insulinotropic peptide [0.243 (0.085, 0.401) nmol/L × min], with no significant differences in the AUCs for amylin, glucagon, and glucagon-like peptide 1.

CONCLUSIONS

Ingestion of the KEβHB-supplemented drink acutely increased the blood βHB concentrations and lowered the plasma glucose concentrations in adults with prediabetes. Further research is needed to investigate the dynamics of repeated ingestions of a KEβHB supplement by individuals with prediabetes, with a view to preventing new-onset diabetes. This trial was registered at www.clinicaltrials.gov as NCT03889210.

Exogenous Ketone Supplementation and Keto-Adaptation for Endurance Performance: Disentangling the Effects of Two Distinct Metabolic States

Ketone bodies (KB) provide an alternative energy source and uniquely modulate substrate metabolism during endurance exercise. Nutritional ketosis (blood KBs > 0.5 mM) can be achieved within minutes via exogenous ketone supplementation or days-to-weeks via conforming to a very low-carbohydrate, ketogenic diet (KD). In contrast to short-term (< 2 weeks) KD ingestion, chronic adherence (> 3 weeks) leads to a state of keto-adaptation. However, despite elevating blood KBs to similar concentrations, exogenous ketone supplementation and keto-adaptation are not similar metabolic states as they elicit diverse and distinct effects on substrate availability and metabolism during exercise; meaning that their influence on endurance exercise performance is different. In contrast to contemporary, high(er)-carbohydrate fuelling strategies, inducing nutritional ketosis is rarely ergogenic irrespective of origin and, in fact, can impair endurance performance. Nonetheless, exogenous ketone supplementation and keto-adaptation possess utility for select endurance events and individuals, thus warranting further research into their performance effects and potential strategies for their optimisation. It is critical, however, that future research considers the limitations of measuring blood KB concentrations and their utilisation, and assess the effect of nutritional ketosis on performance using exercise protocols reflective of real-world competition. Furthermore, to reliably assess the effects of keto-adaptation, rigorous dietary-training controls of sufficient duration should be prioritised.

14-Day Ketone Supplementation Lowers Glucose and Improves Vascular Function in Obesity: A Randomized Crossover Trial

CONTEXT

Postprandial hyperglycemia increases systemic inflammation and is a risk factor for cardiovascular disease. A ketone monoester (KME) drink containing β-hydroxybutyrate (β-OHB) rapidly lowers plasma glucose, which may be a strategy protecting against postprandial hyperglycemia.

OBJECTIVE

We hypothesized that KME would attenuate 2-hour postprandial glucose, lower systemic inflammation, and improve vascular function in adults with obesity.

METHODS

In a randomized crossover design, 14 participants with obesity (age = 56 ± 12 years; body mass index = 32.8 ± 7.7 kg/m2) consumed KME (12 g β-OHB) or placebo 15 minutes prior to each meal for 14 days with all meals provided and matched between conditions. Postprandial glycemia was assessed by continuous glucose monitoring. Vascular function and inflammation were assessed before and after treatment periods.

RESULTS

Postprandial glucose was 8.0% lower in KME versus placebo (g = 0.735; P = 0.011) and 24-hour average glucose reduced by 7.8% (g = 0.686; P = 0.0001). Brachial artery flow-mediated dilation increased from 6.2  ±  1.5% to 8.9 ± 3.3% in KME (g = 1.05; P = 0.0004) with no changes in placebo (condition × time interaction, P = 0.004). There were no changes in plasma cytokines; however, lipopolysaccharide-stimulated monocyte caspase-1 activation was lower following KME supplementation versus placebo (stimulation × condition × time interaction; P = 0.004). The KME supplement was well tolerated by participants and adherence to the supplementation regimen was very high.

CONCLUSIONS

In adults with obesity, 14 days of premeal KME supplementation improves glucose control, enhances vascular function, and may reduce cellular inflammation. KME supplementation may be a viable, nonpharmacological approach to improving and protecting vascular health in people with heightened cardiometabolic risk.

Ketone Therapy for Heart Failure: Current Evidence for Clinical Use

During conditions that result in depleted circulating glucose levels, ketone bodies synthesized in the liver are necessary fuel substrates for the brain. In other organs such as the heart, the reliance on ketones for generating energy is less life threatening as the heart can utilize alternative fuel sources such as fatty acids. However, during pathophysiological conditions such as heart failure, cardiac defects in metabolic processes that normally allow for sufficient energy production from fatty acids and carbohydrates contribute to a decline in contractile function. As such, it has been proposed that the failing heart relies more on ketone bodies as an energy source than previously appreciated. Furthermore, it has been suggested that ketone bodies may function as signaling molecules that can suppress systemic and cardiac inflammation. Thus, it is possible that intentionally elevating circulating ketones may be beneficial as an adjunct treatment for heart failure. Although many approaches can be used for 'ketone therapy', each of these has their own advantages and disadvantages in the treatment of heart failure. Thus, we summarize current preclinical and clinical studies involving various types of ketone therapy in cardiac disease and discuss the advantages and disadvantages of each modality as possible treatments for heart failure.

Toxicological evaluation of the ketogenic ester bis hexanoyl (R)-1,3-butanediol: Subchronic toxicity in Sprague Dawley rats

Bis-hexanoyl (R)-1,3-butanediol (BH-BD) is novel ketone ester undergoing development as a food ingredient to achieve nutritional ketosis in humans. Male and female Crl:CD(SD) rats were administered BH-BD twice daily at 9000, 12,000 or 15,000 mg/kg/day, by oral gavage in a 90-day toxicity study with 28-day recovery period; and an interim 28-day phase. Test substance-related early deaths occurred in four females at 15,000 mg/kg/day. A dose-dependent increase in acute transient postdose (1-3 h) observations of incoordination at ≥12,000 mg/kg/day and decreased activity at all dose levels were noted in both sexes. Postdose observations were likely associated with peak ketonemia and were considered adverse at 15,000 mg/kg/day. These daily observations decreased over the study without any persistent effects, as determined during weekly pre-dose observations. Adverse histopathological changes included ulceration/erosion in non-glandular stomach at ≥ 12,000 mg/k/day and in glandular stomach at 15,000 mg/kg/day. These histopathological findings were not noted after 28-days of recovery. Due to unlikely human relevance of the rat non-glandular stomach effects for BH-BD and test substance-related mortality at 15,000 mg/kg/day, the no-observed-adverse-effect level (NOAEL) for subchronic toxicity of BH-BD was determined to be 12,000 mg/kg/day.

Therapeutic Potential of Ketone Bodies for Patients With Cardiovascular Disease: JACC State-of-the-Art Review

Metabolic perturbations underlie a variety of cardiovascular disease states; yet, metabolic interventions to prevent or treat these disorders are sparse. Ketones carry a negative clinical stigma as they are involved in diabetic ketoacidosis. However, evidence from both experimental and clinical research has uncovered a protective role for ketones in cardiovascular disease. Although ketones may provide supplemental fuel for the energy-starved heart, their cardiovascular effects appear to extend far beyond cardiac energetics. Indeed, ketone bodies have been shown to influence a variety of cellular processes including gene transcription, inflammation and oxidative stress, endothelial function, cardiac remodeling, and cardiovascular risk factors. This paper reviews the bioenergetic and pleiotropic effects of ketone bodies that could potentially contribute to its cardiovascular benefits based on evidence from animal and human studies.

Different Weight Loss Intervention Approaches Reveal a Lack of a Common Pattern of Gut Microbiota Changes

Options for treatment of obesity include dietary approaches and bariatric surgery. Previous studies have shown that weight loss interventions have an impact on gut microbiota. However, a pattern of gut microbiota changes associated with weight loss independently of the type of intervention has not been described yet. This study includes 61 individuals who followed different weight loss strategies in three different trials: 21 followed a hypocaloric Mediterranean diet (MedDiet), 18 followed a very-low-calorie ketogenic diet (VLCKD) and 22 patients underwent sleeve gastrectomy bariatric surgery (BS). Gut microbiota profile was assessed by next-generation sequencing. A common taxon that had significantly changed within the three weight loss interventions could not be find. At the family level, Clostiridiaceae significantly increased its abundance with MedDiet and VLCKD, whilst Porphyromonadacean and Rikenellaceae significantly increased with VLCKD and BS. At genus level, in VLCKD and BS, Parabacteroides and Alistipes significantly increased their abundance whilst Lactobacillus decreased. At the species level, BS and VLCKD produced an increase in Parabacteroidesdistasonis and a decrease in Eubactieriumventriosum and Lactobacillusrogosae, whilst Orodibactersplanchnicus increased its abundance after the BS and MedDiet. Predicted metagenome analysis suggested that most of the changes after VLCKD were focused on pathways related to biosynthesis and degradation/utilization/assimilation, while BS seems to decrease most of the biosynthesis pathways. MedDiet was enriched in several pathways related to fermentation to short-chain fatty acids. Our results show that weight loss is not associated with a specific pattern of gut microbiota changes independently of the strategy used. Indeed, gut microbiota changes according to type of weight loss intervention.

Bicarbonate Unlocks the Ergogenic Action of Ketone Monoester Intake in Endurance Exercise

PURPOSE

We recently reported that oral ketone ester (KE) intake before and during the initial 30 min of a 3 h 15 min simulated cycling race (RACE) transiently decreased blood pH and bicarbonate without affecting maximal performance in the final quarter of the event. We hypothesized that acid-base disturbances due to KE overrules the ergogenic potential of exogenous ketosis in endurance exercise.

METHODS

Nine well-trained male cyclists participated in a similar RACE consisting of 3 h submaximal intermittent cycling (IMT180') followed by a 15-min time trial (TT15') preceding an all-out sprint at 175% of lactate threshold (SPRINT). In a randomized crossover design, participants received (i) 65 g KE, (ii) 300 mg·kg-1 body weight NaHCO3 (BIC), (iii) KE + BIC, or (iv) a control drink (CON), together with consistent 60 g·h-1 carbohydrate intake.

RESULTS

KE ingestion transiently elevated blood D-ß-hydroxybutyrate to ~2-3 mM during the initial 2 h of RACE (P < 0.001 vs CON). In KE, blood pH concomitantly dropped from 7.43 to 7.36 whereas bicarbonate decreased from 25.5 to 20.5 mM (both P < 0.001 vs CON). Additional BIC resulted in 0.5 to 0.8 mM higher blood D-ß-hydroxybutyrate during the first half of IMT180' (P < 0.05 vs KE) and increased blood bicarbonate to 31.1 ± 1.8 mM and blood pH to 7.51 ± 0.03 by the end of IMT180' (P < 0.001 vs KE). Mean power output during TT15' was similar between KE, BIC, and CON at ~255 W but was 5% higher in KE + BIC (P = 0.02 vs CON). Time to exhaustion in the sprint was similar between all conditions at ~60 s (P = 0.88). Gastrointestinal symptoms were similar between groups.

DISCUSSION

The coingestion of oral bicarbonate and KE enhances high-intensity performance at the end of an endurance exercise event without causing gastrointestinal distress.

A comparison of the satiating properties of medium-chain triglycerides and conjugated linoleic acid in participants with healthy weight and overweight or obesity

PURPOSE

Inconsistent evidence exists for greater satiety after medium-chain triglycerides (MCT) or conjugated linoleic acid (CLA) compared to long-chain triglycerides (LCT). Furthermore, the mechanisms are poorly understood and effects in people with a healthy weight and those with overweight/obesity have not been compared. This study aimed to compare appetite responses in these groups and examine the mechanisms behind any differences.

METHODS

Fifteen participants with healthy weight (BMI: 22.7 ± 1.9 kg·m-2) and fourteen participants with overweight/obesity (BMI: 30.9 ± 3.9 kg·m-2) consumed a breakfast containing either 23.06 g vegetable oil (CON), 25.00 g MCT oil (MCT), or 6.25 g CLA and 16.80 g vegetable oil (CLA). Appetite, peptide YY (PYY), total ghrelin (TG), β-hydroxybutyrate, and gastric emptying (GE) were measured throughout. Energy intake was assessed at an ad libitum lunch and throughout the following ~ 36 h.

RESULTS

Neither MCT nor CLA decreased ad libitum intake; however MCT decreased day 1 energy intake (P = 0.031) and the 48-h period (P = 0.005) compared to CON. MCT delayed GE (P ≤ 0.01) compared to CON, whereas CLA did not. PYY and TG concentrations were not different (P = 0.743 and P = 0.188, respectively), but MCT increased β-hydroxybutyrate concentrations compared to CON (P = 0.005) and CLA (P < 0.001). β-hydroxybutyrate concentrations were higher in participants with overweight/obesity (P = 0.009).

CONCLUSION

Consumption of MCT reduces energy intake in the subsequent 48 h, whereas CLA does not. Delayed gastric emptying or increased β-hydroxybutyrate concentrations may mediate this.

Exogenous Ketones Lower Post-exercise Acyl-Ghrelin and GLP-1 but Do Not Impact Ad libitum Energy Intake

Ketosis and exercise are both associated with alterations in perceived appetite and modification of appetite-regulating hormones. This study utilized a ketone ester (R)-3-hydroxybutyl (R)-3-hydroxybutyrate (KE) to examine the impact of elevated ketone body D-β-hydroxybutyrate (βHB) during and after a bout of exercise on appetite-related hormones, appetite perception, and ad libitum energy intake over a 2 h post-exercise period. In a randomized crossover trial, 13 healthy males and females (age: 23.6 ± 2.4 years; body mass index: 25.7 ± 3.2 kg·m⁻²) completed an exercise session @ 70% VO_2peak for 60 min on a cycling ergometer and consumed either: (1) Ketone monoester (KET) (0.5 g·kg⁻¹ pre-exercise + 0.25 g·kg⁻¹ post-exercise); or (2) isocaloric dextrose control (DEX). Transient ketonaemia was achieved with βHB concentrations reaching 5.0 mM (range 4.1–6.1 mM) during the post-exercise period. Relative to the dextrose condition, acyl-ghrelin (P = 0.002) and glucagon-like peptide-1 (P = 0.038) were both reduced by acute ketosis immediately following exercise. AUC for acyl-ghrelin was lower in KET compared to DEX (P = 0.001), however there were no differences in AUC for GLP-1 (P = 0.221) or PYY (P = 0.654). Perceived appetite (hunger, P = 0.388; satisfaction, P = 0.082; prospective food consumption, P = 0.254; fullness, P = 0.282) and 2 h post-exercise ad libitum energy intake (P = 0.488) were not altered by exogenous ketosis. Although KE modifies homeostatic regulators of appetite, it does not appear that KE acutely alters energy intake during the post-exercise period in healthy adults.

Nutritional Ketosis as a Potential Treatment for Alcohol Use Disorder

Alcohol use disorder (AUD) is a chronic, relapsing brain disorder, characterized by compulsive alcohol seeking and disrupted brain function. In individuals with AUD, abstinence from alcohol often precipitates withdrawal symptoms than can be life threatening. Here, we review evidence for nutritional ketosis as a potential means to reduce withdrawal and alcohol craving. We also review the underlying mechanisms of action of ketosis. Several findings suggest that during alcohol intoxication there is a shift from glucose to acetate metabolism that is enhanced in individuals with AUD. During withdrawal, there is a decline in acetate levels that can result in an energy deficit and could contribute to neurotoxicity. A ketogenic diet or ingestion of a ketone ester elevates ketone bodies (acetoacetate, β-hydroxybutyrate and acetone) in plasma and brain, resulting in nutritional ketosis. These effects have been shown to reduce alcohol withdrawal symptoms, alcohol craving, and alcohol consumption in both preclinical and clinical studies. Thus, nutritional ketosis may represent a unique treatment option for AUD: namely, a nutritional intervention that could be used alone or to augment the effects of medications.

Beta-Hydroxybutyrate, Friend or Foe for Stressed Hearts

One of the characteristics of the failing human heart is a significant alteration in its energy metabolism. Recently, a ketone body, β-hydroxybutyrate (β-OHB) has been implicated in the failing heart’s energy metabolism as an alternative “fuel source.” Utilization of β-OHB in the failing heart increases, and this serves as a “fuel switch” that has been demonstrated to become an adaptive response to stress during the heart failure progression in both diabetic and non-diabetic patients. In addition to serving as an alternative “fuel,” β-OHB represents a signaling molecule that acts as an endogenous histone deacetylase (HDAC) inhibitor. It can increase histone acetylation or lysine acetylation of other signaling molecules. β-OHB has been shown to decrease the production of reactive oxygen species and activate autophagy. Moreover, β-OHB works as an NLR family pyrin domain-containing protein 3 (Nlrp3) inflammasome inhibitor and reduces Nlrp3-mediated inflammatory responses. It has also been reported that β-OHB plays a role in transcriptional or post-translational regulations of various genes’ expression. Increasing β-OHB levels prior to ischemia/reperfusion injury results in a reduced infarct size in rodents, likely due to the signaling function of β-OHB in addition to its role in providing energy. Sodium-glucose co-transporter-2 (SGLT2) inhibitors have been shown to exert strong beneficial effects on the cardiovascular system. They are also capable of increasing the production of β-OHB, which may partially explain their clinical efficacy. Despite all of the beneficial effects of β-OHB, some studies have shown detrimental effects of long-term exposure to β-OHB. Furthermore, not all means of increasing β-OHB levels in the heart are equally effective in treating heart failure. The best timing and therapeutic strategies for the delivery of β-OHB to treat heart disease are unknown and yet to be determined. In this review, we focus on the crucial role of ketone bodies, particularly β-OHB, as both an energy source and a signaling molecule in the stressed heart and the overall therapeutic potential of this compound for cardiovascular diseases.

Exogenous Ketones as Therapeutic Signaling Molecules in High-Stress Occupations: Implications for Mitigating Oxidative Stress and Mitochondrial Dysfunction in Future Research

High-stress occupations (ie, firefighters, military personnel, police officers, etc.) are often plagued by cardiometabolic diseases induced by exposure to chronic stressors. Interrupted sleep cycles, poor dietary patterns, lack of physical activity, and smoke exposure along with simultaneous psychological stressors promote chronic low-grade inflammation and excessive oxidative stress. Collectively, these data suggest that practical interventions which might mitigate the underlying pathologies of these cardiometabolic diseases are warranted. Ketones, specifically R-βHB, modulates intracellular signaling cascades such as the cellular redox ratios of NAD+/NADH, the activity of NAD dependent deacetylases SIRT1 and SIRT3, and promotes a robust mitochondrial environment which favors reductions in oxidative stress and inflammation. To date, the literature examining R-βHB as a signaling metabolite has mostly been performed from endogenous R-βHB production achieved through nutritional ketosis or cell culture and mouse models using exogenous R-βHB. To the authors knowledge, only 1 study has attempted to report on the effects of exogenous ketones and the mitigation of oxidative stress/inflammation. Therefore, the scope of this review is to detail the mechanisms of R-βHB as a signaling metabolite and the role that exogenous ketones might play in mitigating diseases in individuals serving in high-stress occupations.

Beta-hydroxybutyrate, an endogenous NLRP3 inflammasome inhibitor, attenuates anxiety-related behavior in a rodent post-traumatic stress disorder model

Accumulating evidence suggests that elevated inflammation contributes to the pathophysiology of post-traumatic stress disorder (PTSD) and that anti-inflammatory drugs might be a new treatment strategy for PTSD. It has been reported that beta-hydroxybutyrate (BHB), one of the main ketone bodies produced, can have an anti-inflammatory and antidepressant effect. Here, we investigated the potential anti-anxiety and anti-inflammatory effects of BHB using a rodent PTSD model, induced by single prolonged stress (SPS). Male, Sprague–Dawley rats were employed in this study. Repeated administration of BHB attenuated SPS-induced anxiety-related behaviors evaluated by the elevated plus maze test. SPS increased the serum levels of TNF-α and IL-1β. In contrast, BHB administration partially attenuated the increase of serum TNF-α. These findings demonstrate that BHB exerts its anxiolytic effects, possibly by inhibiting systemic TNF-α. Hence, BHB may be a novel therapeutic candidate for the treatment of PTSD.

Association Between Ketosis and Changes in Appetite Markers with Weight Loss Following a Very Low-Energy Diet

OBJECTIVE

The purpose of this study was to examine whether the degree of ketosis, measured as plasma β-hydroxybutyrate (βHB) in fasting, was associated with changes in appetite feelings and plasma concentration of appetite-related hormones after weight loss.

METHODS

A total of 87 individuals with obesity (BMI: 36.5 ± 4.0 kg/m² ; age: 42.4 ± 9.7 years; 39 males) underwent 8 weeks of a very low-energy diet. Body weight/composition, plasma concentration of βHB, and appetite-related hormones (active ghrelin, active glucagon-like peptide 1 [GLP-1], total peptide YY, cholecystokinin [CCK], and insulin) and subjective appetite feelings were measured at baseline and week 9.

RESULTS

Participants lost 17.7 ± 4.1 kg and were ketotic (βHB: 1.24 ± 0.82 mmol/L in fasting) at week 9. A negative association was found between βHB in fasting at week 9 and changes in basal (r = -0.315, P = 0.003) and postprandial ghrelin concentration (r = -0.286, P = 0.008), and a positive association was found with the change in postprandial GLP-1 (r = 0.244, P = 0.025) and CCK (r = 0.228, P = 0.035). No association was seen between βHB in fasting and changes in peptide YY or subjective feelings of appetite.

CONCLUSIONS

βHB plasma concentration in fasting is associated with lower concentrations of the hunger hormone ghrelin and increased concentrations of the satiety hormones GLP-1 and CCK. Future studies should explore the molecular mechanisms by which βHB modulates the secretion of gut hormones.

In vitro stability and in vivo pharmacokinetics of the novel ketogenic ester, bis hexanoyl (R)-1,3-butanediol

A novel ketone ester, bis hexanoyl (R)-1,3-butanediol (BH-BD), has been developed as a means to elevate blood ketones, for use as an energy substrate and a signaling metabolite. The metabolism of BH-BD and its effects on blood beta-hydroxybutyrate (BHB) levels was evaluated in various in vitro matrices and through analysis of plasma collected from Sprague Dawley rats and C57/BL6 mice in two oral gavage studies. A well-characterized ketone ester, (R)-3-hydroxybutyl (R)-3-hydroxybutyrate (HB-BHB), was used as an active control throughout. In vitro assay results demonstrated that BH-BD likely remains intact in the stomach and is hydrolyzed in the small intestine into hexanoate and (R)-1,3-butanediol. If absorbed intact, BH-BD is subject to hydrolysis by non-CYP enzymes in liver and esterases in plasma. If BH-BD reaches the lower intestine it is metabolized by gut flora. Plasma BHB delivery increased in a dose-dependent manner in rats and mice following oral administration of BH-BD. All doses of BH-BD were well tolerated. At doses over 3 g/kg, BHB delivery was similar between BH-BD and HB-BHB. The results of these studies support the hydrolysis of BH-BD into hexanoate and (R)-1,3-butanediol which are metabolized into BHB, delivering a well-tolerated, sustained and dose-dependent increase in plasma BHB in rodents.

Islet Health, Hormone Secretion, and Insulin Responsivity with Low-Carbohydrate Feeding in Diabetes

Exploring new avenues to control daily fluctuations in glycemia has been a central theme for diabetes research since the Diabetes Control and Complications Trial (DCCT). Carbohydrate restriction has re-emerged as a means to control type 2 diabetes mellitus (T2DM), becoming increasingly popular and supported by national diabetes associations in Canada, Australia, the USA, and Europe. This approval comes from many positive outcomes on HbA1c in human studies; yet mechanisms underlying their success have not been fully elucidated. In this review, we discuss the preclinical and clinical studies investigating the role of carbohydrate restriction and physiological elevations in ketone bodies directly on pancreatic islet health, islet hormone secretion, and insulin sensitivity. Included studies have clearly outlined diet compositions, including a diet with 30% or less of calories from carbohydrates.

Potential Therapeutic Effects of Exogenous Ketone Supplementation for Type 2 Diabetes: A Review

Type 2 diabetes (T2D) is among the most prevalent non-communicable lifestyle diseases. We propose that overnutrition and low levels of physical activity can contribute to a vicious cycle of hyperglycemia, inflammation and oxidative stress, insulin resistance, and pancreatic β-cell dysfunction. The pathophysiological manifestations of T2D have a particular impact on the vasculature and individuals with T2D are at high risk of cardiovascular disease. Targeting aspects of the vicious cycle represent therapeutic approaches for improving T2D and protecting against cardiovascular complications. The recent advent of exogenous oral ketone supplements represents a novel, non-pharmacological approach to improving T2D pathophysiology and potentially protecting against cardiovascular disease risk. Herein, we review the emerging literature regarding the effects of exogenous ketone supplementation on metabolic control, inflammation, oxidative stress, and cardiovascular function in humans and highlight the potential application for breaking the vicious cycle of T2D pathophysiology.

Oral D/L-3-Hydroxybutyrate Stimulates Cholecystokinin and Insulin Secretion and Slows Gastric Emptying in Healthy Males

BACKGROUND

D-3-hydroxybutyrate (D-3-OHB) is a ketone body that serves as an alternative nutritional fuel but also as an important signaling metabolite. Oral ketone supplements containing D/L-3-OHB are becoming a popular approach to achieve ketosis.

AIM

To explore the gut-derived effects of ketone supplements.

METHODS

Eight healthy lean male volunteers were investigated on 2 separate occasions:An acetaminophen test was performed to evaluate gastric emptying and blood samples were obtained consecutively throughout the study period.

RESULTS

We show that oral consumption of D/L-3-OHB stimulates cholecystokinin release (P = 0.02), elevates insulin (P = 0.03) and C-peptide (P < 0.001) concentrations, and slows gastric emptying (P = 0.01) compared with matched intravenous D/L-3-OHB administration. Measures of appetite and plasma concentrations of glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) were unaffected by interventions.

CONCLUSION

Our findings show that D/L-3-OHB exert incretin effects and indicate luminal sensing in the gut endothelium. This adds to our understanding of ketones as signaling metabolites and displays the important difference between physiological ketosis and oral ketone supplements.

Low carbohydrate ketogenic therapy as a metabolic treatment for binge eating and ultraprocessed food addiction

PURPOSE OF REVIEW

The aim of this study was to highlight the recent advancements and future directions for potential use of a low carbohydrate ketogenic dietary approach to treat binge eating and ultraprocessed food addiction. Herein, we explore proposed mechanisms of why a diet low in refined carbohydrates, processed sugar and higher fat content may be helpful in alleviating symptoms.

RECENT FINDINGS

Emerging evidence suggests there may be a metabolic role in development of maladaptive eating. These findings broaden our understanding of eating psychopathology causes. Ultraprocessed, refined or high glycemic index carbohydrates are a possible trigger mediating neurochemical responses similar to addiction. The carbohydrate-insulin model of obesity supports observations of these foods triggering abnormal blood sugar and insulin spikes subsequently leading to changes in metabolic and neurobiological signaling. This results in overeating symptoms and hunger exacerbation, which differs from observed effects of healthy fat consumption and lack of similar insulin spikes. As supported in recent case series, significantly reducing or abstaining from these addictive-like ultraprocessed foods and highly refined carbohydrates could be considered a treatment approach.

SUMMARY

The current review highlights recent and pertinent evidence with respect to theoretical and practical application of low carbohydrate ketogenic therapeutic approaches for ultraprocessed food addiction and binge eating symptoms. VIDEO ABSTRACT:.

Ketonemia and Glycemia Affect Appetite Levels and Executive Functions in Overweight Females During Two Ketogenic Diets

OBJECTIVE

This study sought to investigate how glycemia and ketonemia variations during two ketogenic diet protocols affect appetite, executive functions, and mood in young women with overweight.

METHODS

Fifty healthy young females with overweight were randomly assigned to (1) a ketogenic diet without any restriction on energy intake, (2) a commercial energy-restricted ketogenic Mediterranean diet, and (3) an energy-restricted Mediterranean diet for 10 days. A visual analogue scale was used to test appetite, and one mood test and two cognitive tasks (working memory and inhibition control) were performed. Moreover, body composition, fasting blood glucose, and β-hydroxybutyrate (BHB) were measured.

RESULTS

A positive correlation was found between glycemia and appetite (P = 0.019), unfullness score (P =  0.001), and desire to eat (P = 0.030) (pre- and postdiet levels). Postdiet BHB levels showed a positive correlation with fullness score (P = 0.002) and a negative correlation with appetite (P = 0.022) and desire to eat (P = 0.009). A positive correlation was found between prediet levels of glycemia and reaction times in the go-trials of the executive function test (P = 0.018). Postdiet BHB level showed a negative correlation with the accuracy of the no-go trials (P = 0.027).

CONCLUSIONS

Ketogenic diets, compared with a Mediterranean diet, have a greater effect in terms of appetite reduction but might affect inhibition functions.

Prior ingestion of a ketone monoester supplement reduces postprandial glycemic responses in young healthy-weight individuals

The main objective of this study was to determine whether acute ingestion of a ketone monoester (KME) supplement impacted mixed-meal tolerance test (MMTT) glucose area under the curve (AUC). Nineteen healthy young volunteers (10 males/9 females; age, 24.7 ± 4.9 years; body mass index, 22.7 ± 2.4 kg/m²) participated in a double-blind, placebo-controlled crossover study. Following overnight fasting (≥10 h), participants consumed 0.45 mL/kg of a KME supplement or taste-matched placebo followed by an MMTT 15 min later. Blood samples were collected every 15-30 min over 2.5 h. KME supplementation acutely raised β-hydroxybutyrate AUC (590%, P < 0.0001, d = 2.4) and resulted in decreases in blood glucose AUC (-9.4%, P = 0.03, d = 0.56) and nonesterified fatty acid (NEFA) AUC (-27.3%, P = 0.023, d = 0.68) compared with placebo. No differences were found for plasma insulin AUC (P = 0.70) or gastric emptying estimated by co-ingested acetaminophen AUC (P = 0.96) between ketone and placebo. Overall, results indicate that KME supplementation attenuates postprandial glycemic and NEFA responses when taken 15 min prior to a mixed meal in young healthy individuals. Future studies are warranted to investigate whether KME supplementation may benefit individuals with impaired glycemic control. Novelty: Acute ketone monoester supplementation 15 min prior to a mixed meal decreased postprandial glucose and NEFA levels without significantly impacting postprandial insulin or estimates of gastric emptying. Glucose- and NEFA-lowering effects of ketone monoester supplementation are apparently not mediated by changes in insulin release or gastric emptying.

Very low calorie ketogenic diets in overweight and obesity treatment: Effects on anthropometric parameters, body composition, satiety, lipid profile and microbiota

According to the World Health Organization (WHO) the prevalence of obesity tripled worldwide since 1975. Obesity prevention and treatment is based upon lifestyle changes involving eating habits, physical activity and behaviour therapy. Various dietary patterns have been used as nutritional strategies and, in recent years, interest has been shown in very low calorie ketogenic diets (VLCKD) that provide less than 800 calories (kcal), no more than 20-50 g/day of carbohydrates and 0.8-1.5 g/kg ideal body weight of protein. We conducted a literature review of all clinical trials published between January 2014-November 2019 on people with obesity (PWO) that evaluated VLCKD effects on anthropometric parameters, body composition, satiety, lipid profile and microbiota. Findings from literature showed that VLCKD could be useful to ameliorate the quality of life and sleep of PWO. It leads to a rapid weight loss and results in improvements in body mass index (BMI = kg/m²), waist circumference and fat mass reduction preserving lean body mass and resting metabolic rate. This eating pattern reduced the desire to eat and increased satiety. Little is known regarding the effects of VLCKD on the microbiota of PWO for which it is important to conduct further studies.

Appetite control: hormones or diet strategies?

PURPOSE OF REVIEW

Appetite control results from metabolic, behavioral, and environmental factors that influence hunger and the desire to eat. We summarize the latest advances in the hormonal and nutritional strategies to control appetite and reduce hunger.

RECENT FINDINGS

The fed-hunger-state is regulated by central and peripheric hormones, which modulate energy balance. Leptin, insulin, ghrelin, peptide YY (PYY), and other gut-derived peptides represent the main appetite controllers. The role of orexins, obestatin, and liver-expressed antimicrobial peptide 2 has been uncovered recently. New insights have demonstrated the role of hippocampal activity as a possible mechanism of action. Glucagon-like peptide 1 (GLP1) receptor agonists are well known agents controlling appetite. Association of GLP1 receptor agonist, PYY, or glucose-dependent insulinotropic polypeptide agonists have been tested as new approaches. Appetite-control hormones have also risen as factors involved in the efficacy of bariatric procedures. High-protein, ketogenic diet, and intermittent fasting have been described as nutritional strategies to reduce appetite, although the physiological mechanism and long-term safety remains unclear.

SUMMARY

Appetite control has been an important target for the treatment of obesity and associated disorders. New studies have demonstrated promising adoption of dietary approaches, hormone-based drugs, and bariatric surgery to control energy intake. Further research will establish a significant association, benefits, and safety of these new therapies.

Caloric restriction, resting metabolic rate and cognitive performance in Non-obese adults: A post-hoc analysis from CALERIE study

Physical activity (PA) has been proposed as a determinant of cognitive function and is one component of energy balance (EB). EB is the difference between energy intake (EI) and the total daily energy expenditure (TDEE). TDEE is a combination of resting metabolic rate (RMR), thermic effect of food and PA. The potential role of each of these components on cognitive function has not yet been systemically investigated. We aim to evaluate the association between each component of EB on cognition, using baseline and longitudinal data from a clinical trial of caloric restriction (CR). This is a parallel-group, randomized clinical trial comparing two years of 25% CR with two years of ad libitum diet (AL), with 220 healthy volunteers of both sex, aged between 21 and 50 years and initial BMI ≥ 22 kg/m2 and <28 kg/m2. Body weight, fat mass (FM), fat-free mass (FFM), and bone mineral content were evaluated, as well as RMR, TDEE, cognitive performance and baseline energy intake. A 30 min/day of a moderate level on a minimum of 5 days/week was advised as PA measure. Longitudinal analysis demonstrated that the influence of CR in the improvement of cognitive performance was moderated by changes in RMR, suggesting that in individuals submitted to CR, the cognitive performance and the RMR improved proportionally, independently of changes in EI and body mass. EB and homeostasis are crucial to modulate the RMR. Moreover, RMR presents an important influence on cognitive function in individuals submitted to CR in a long term.

The Implication of Gut Hormones in the Regulation of Energy Homeostasis and Their Role in the Pathophysiology of Obesity

PURPOSE OF REVIEW

This review provides an update on the role of gut hormones and their interactions in the regulation of energy homeostasis, describes gut hormone adaptations in obesity and in response to weight loss, and summarizes the current evidence on the role of gut hormone-based therapies for obesity treatment.

RECENT FINDINGS

Gut hormones play a key role in regulating eating behaviour, energy and glucose homeostasis. Dysregulated gut hormone responses have been proposed to be pathogenetically involved in the development and perpetuation of obesity. Summarizing the major gut hormone changes in obesity, obese individuals are characterized by blunted postprandial ghrelin suppression, loss of premeal ghrelin peaks, impaired diurnal ghrelin variability and reduced fasting and postprandial levels of anorexigenic peptides. Adaptive alterations of gut hormone levels are implicated in weight regain, thus complicating hypocaloric dietary interventions, and can further explain the profound weight loss and metabolic improvement following bariatric surgery. A plethora of compounds mimicking gut hormone changes after bariatric surgery are currently under investigation, introducing a new era in the pharmacotherapy of obesity. The current trend is to combine different gut hormone receptor agonists and target multiple systems simultaneously, in order to replicate as closely as possible the gut hormone milieu after bariatric surgery and circumvent the counter-regulatory adaptive changes associated with dietary energy restriction. An increasing number of preclinical and early-phase clinical trials reveal the additive benefits obtained with dual or triple gut peptide receptor agonists in reducing body weight and improving glycaemia. Gut hormones act as potent regulators of energy and glucose homeostasis. Therapeutic strategies targeting their levels or receptors emerge as a promising approach to treat patients with obesity and hyperglycaemia.

Mental, emotional, and behavioral effects of ketogenic diet for non-epileptic neuropsychiatric conditions

Ketogenic diet (KD) is comprised of a distinct macronutrient combination: i.e. 90% fat, 8% of protein and 2% of carbohydrates, typically characterized as a high-fat low-carbohydrate diet. KD's efficacy was largely established for treatment resistant epilepsy in children, but its mental, emotional and behavioral effects remain largely unknown. Nevertheless, the efficacious effects of KD in childhood epilepsy provide rationale for repurposing this approach for other brain-based disorders. Consequently, clinicians and researchers should be aware of the evidence regarding efficacy, as well as the benefits and risks of adopting this diet. Results from animals and humans studies provide equivocal evidence across multiple domains of psychopathology. Conceptually, KD shows promise to serve as an efficacious treatment for mental disorders.

Nutritional ketosis improves exercise metabolism in patients with very long-chain acyl-CoA dehydrogenase deficiency

A maladaptive shift from fat to carbohydrate (CHO) oxidation during exercise is thought to underlie myopathy and exercise-induced rhabdomyolysis in patients with fatty acid oxidation (FAO) disorders. We hypothesised that ingestion of a ketone ester (KE) drink prior to exercise could serve as an alternative oxidative substrate supply to boost muscular ATP homeostasis. To establish a rational basis for therapeutic use of KE supplementation in FAO, we tested this hypothesis in patients deficient in Very Long-Chain acyl-CoA Dehydrogenase (VLCAD). Five patients (range 17-45 y; 4 M/1F) patients were included in an investigator-initiated, randomised, blinded, placebo-controlled, 2-way cross-over study. Patients drank either a KE + CHO mix or an isocaloric CHO equivalent and performed 35 minutes upright cycling followed by 10 minutes supine cycling inside a Magnetic Resonance scanner at individual maximal FAO work rate (fatmax; approximately 40% VO₂ max). The protocol was repeated after a 1-week interval with the alternate drink. Primary outcome measures were quadriceps phosphocreatine (PCr), Pi and pH dynamics during exercise and recovery assayed by in vivo ³¹ P-MR spectroscopy. Secondary outcomes included plasma and muscle metabolites and respiratory gas exchange recordings. Ingestion of KE rapidly induced mild ketosis and increased muscle BHB content. During exercise at FATMAX, VLCADD-specific plasma acylcarnitine levels, quadriceps glycolytic intermediate levels and in vivo Pi/PCr ratio were all lower in KE + CHO than CHO. These results provide a rational basis for future clinical trials of synthetic ketone ester supplementation therapy in patients with FAO disorders. Trial registration: ClinicalTrials.gov. Protocol ID: NCT03531554; METC2014.492; ABR51222.042.14.

No Benefit of Ingestion of a Ketone Monoester Supplement on 10-km Running Performance

PURPOSE

Preexercise ingestion of exogenous ketones alters the metabolic response to exercise, but effects on exercise performance have been equivocal.

METHODS

On two occasions in a double-blind, randomized crossover design, eight endurance-trained runners performed 1 h of submaximal exercise at approximately 65% V˙O2max immediately followed by a 10-km self-paced time trial (TT) on a motorized treadmill. An 8% carbohydrate-electrolyte solution was consumed before and during exercise, either alone (CHO + PLA), or with 573 mg·kg of a ketone monoester supplement (CHO + KME). Expired air, HR, and RPE were monitored during submaximal exercise. Serial venous blood samples were assayed for plasma glucose, lactate, and β-hydroxybutyrate concentrations.

RESULTS

CHO + KME produced plasma β-hydroxybutyrate concentrations of approximately 1.0 to 1.3 mM during exercise (P < 0.001), but plasma glucose and lactate concentrations were similar during exercise in both trials. V˙O2, running economy, respiratory exchange ratio, HR, and RPE were also similar between trials. Performance in the 10-km TT was not different (P = 0.483) between CHO + KME (mean, 2402 s; 95% confidence interval, 2204-2600 s) and CHO + PLA (mean, 2422 s; 95% confidence interval, 2217-2628 s). Cognitive performance, measured by reaction time and a multitasking test, did not differ between trials.

CONCLUSIONS

Compared with carbohydrate alone, coingestion of KME by endurance-trained athletes elevated plasma β-hydroxybutyrate concentrations, but did not improve 10-km running TT or cognitive performance.

Exogenous ketosis impacts neither performance nor muscle glycogen breakdown in prolonged endurance exercise

Available evidence indicates that ketone bodies inhibit glycolysis in contracting muscles. Therefore, we investigated whether acute exogenous ketosis by oral ketone ester (KE) intake early in a simulated cycling race can induce transient glycogen sparing by glycolytic inhibition, thereby increasing glycogen availability in the final phase of the event. In a randomized crossover design, 12 highly trained male cyclists completed a simulated cycling race (RACE), which consisted of 3-h intermittent cycling (IMT_180′), a 15-min time trial (TT_15′), and a maximal sprint (SPRINT). During RACE, subjects received 60 g carbohydrates/h combined with three boluses (25, 20, and 20 g) (R)-3-hydroxybutyl (R)-3-hydroxybutyrate (KE) or a control drink (CON) at 60 and 20 min before and at 30 min during RACE. KE intake transiently increased blood d-β-hydroxybutyrate to ~3 mM (range: 2.6–5.2 mM) during the first half of RACE (P < 0.001 vs. CON). Blood pH concomitantly decreased from approximately 7.42 to 7.36 (range: 7.29–7.40), whereas bicarbonate dropped from 26.0 to 21.6 mM (range: 20.1–23.7; both P < 0.001 vs. CON)_. Net muscle glycogen breakdown during IMT_180′ [KE: −78 ± 30 (SD); CON: −60 ± 22 mmol/kg wet wt; P = 0.08] and TT_15′ (KE: −9 ± 18; CON: −18 ± 18 mmol/kg wet wt; P = 0.35) was similar between KE and CON. Accordingly, mean power output during TT_15′ (KE: 273 ± 38; CON: 272 ± 37 W; P = 0.83) and time-to-exhaustion in the SPRINT (KE: 59 ± 16; CON: 58 ± 17 s; P = 0.66) were similar between conditions. In conclusion, KE intake during a simulated cycling race does not cause glycogen sparing, nor does it affect all-out performance in the final stage of a simulated race.

NEW & NOTEWORTHY Exogenous ketosis produced by oral ketone ester ingestion during the early phase of prolonged endurance exercise and against the background of adequate carbohydrate intake neither causes muscle glycogen sparing nor improves performance in the final stage of the event. However, such exogenous ketosis may decrease buffering capacity in the approach of the final episode of the event. Furthermore, ketone ester intake during exercise may reduce appetite immediately after exercise.

Alternative substrate metabolism depends on cerebral metabolic state following traumatic brain injury

Decreases in energy metabolism following traumatic brain injury (TBI) are attributed to impairment of glycolytic flux and oxidative phosphorylation. Glucose utilization post-TBI is decreased while administration of alternative substrates has been shown to be neuroprotective. Changes in energy metabolism following TBI happens in two phases; a period of hyper-metabolism followed by prolonged hypo-metabolism. It is not understood how different cerebral metabolic states may impact substrate metabolism and ultimately mitochondrial function. Adult male or female Sprague Dawley rats were given sham surgery or controlled cortical impact (CCI) and were assigned one of two administration schemes. Glucose, lactate or beta-hydroxybutyrate (BHB) were infused i.v. either starting immediately after injury or beginning 6 h post-injury for 3 h to reflect the hyper- and hypo-metabolic stages. Animals were euthanized 24 h post-injury. The peri-contusional cortex was collected and assayed for mitochondrial respiration peroxide production, and citrate synthase activity. Tissue acetyl-CoA, ATP, glycogen and HMGB1 were also quantified. Sex differences were observed in injury pattern. Administration based on cerebral metabolic state identified that only early lactate and late BHB improved mitochondrial function and peroxide production and TCA cycle intermediates in males. In contrast, both early and late BHB had deleterious effects on all aspects of metabolic measurements in females. These data stress there is no one optimal alternative substrate, but rather the fuel type used should be guided by both cerebral metabolic state and sex.

Biomarkers of appetite: is there a potential role for metabolomics?

Knowing the biological signals associated with appetite control is crucial for understanding the regulation of food intake. Biomarkers of appetite have been defined as physiological measures that relate to subjective appetite ratings, measured food intake, or both. Several metabolites including amino acids, lipids and glucose were proposed as key molecules associated with appetite control over 60 years ago, and along with bile acids are all among possible appetite biomarker candidates. Additional metabolites that have been associated with appetite include endocannabinoids, lactate, cortisol and β-hydroxybutyrate. However, although appetite is a complex integrative process, studies often investigated a limited number of markers in isolation. Metabolomics involves the study of small molecules or metabolites present in biological samples such as urine or blood, and may present a powerful approach to further the understanding of appetite control. Using multiple analytical techniques allows the characterisation of molecules, such as carbohydrates, lipids, amino acids, bile acids and fatty acids. Metabolomics has proven successful in identifying markers of consumption of certain foods and biomarkers implicated in several diseases. However, it has been underexploited in appetite control or obesity. The aim of the present narrative review is to: (1) provide an overview of existing metabolites that have been identified in human biofluids and associated with appetite control; and (2) discuss the potential of metabolomics to deepen understanding of appetite control in humans.

Low and reduced carbohydrate diets: challenges and opportunities for type 2 diabetes management and prevention

Low-carbohydrate diets (LCD) have been promoted for weight control and type 2 diabetes (T2D) management, based on an emerging body of evidence, including meta-analyses with an indication of publication bias. Proposed definitions vary between 50 and 130 g/d, or <10 and <40 % of energy from carbohydrate, with no consensus on LCD compositional criteria. LCD are usually followed with limited consideration for other macronutrients in the overall diet composition, introducing variance in the constituent foods and in metabolic responses. For weight management, extensive evidence supports LCD as a valid weight loss treatment, up to 1-2 years. Solely lowering carbohydrate intake does not, in the medium/long term, reduce HbA1c for T2D prevention or treatment, as many mechanisms interplay. Under controlled feeding conditions, LCD are not physiologically or clinically superior to diets with higher carbohydrates for weight-loss, fat loss, energy expenditure or glycaemic outcomes; indeed, all metabolic improvements require weight loss. Long-term evidence also links the LCD pattern to increased CVD risks and mortality. LCD can lead to micronutrient deficiencies and increased LDL-cholesterol, depending on food selection to replace carbohydrates. Evidence is limited but promising regarding food choices/sources to replace high-carbohydrate foods that may alleviate the negative effects of LCD, demanding further insight into the dietary practice of medium to long term LCD followers. Long-term, high-quality studies of LCD with different food sources (animal and/or plant origins) are needed, aiming for clinical endpoints (T2D incidence and remission, cardiovascular events, mortality). Ensuring micronutrient adequacy by food selection or supplementation should be considered for people who wish to pursue long-term LCD.

Medium Chain Triglycerides induce mild ketosis and may improve cognition in Alzheimer's disease. A systematic review and meta-analysis of human studies

INTRODUCTION/AIM

The brain in Alzheimer's disease shows glucose hypometabolism but may utilize ketones for energy production. Ketone levels can potentially be boosted through oral intake of Medium Chain Triglycerides (MCTs). The aim of this meta-analysis is to investigate the effect of MCTs on peripheral ketone levels and cognitive performance in patients with mild cognitive impairment and Alzheimer's disease.

METHODS

Medline, Scopus and Web of Science were searched for literature up to March 1, 2019. Meta-analyses were performed by implementing continuous random-effects models and outcomes were reported as weighted Mean Differences (MDs) or Standardized Mean Differences (SMDs).

RESULTS

Twelve records (422 participants) were included. Meta-analysis of RCTs showed that, compared with placebo, MCTs elevated beta-hydroxybutyrate [MD = 0.355; 95 % CI (0.286, 0.424), I² = 0 %], showed a trend towards cognitive improvement on ADAS-Cog [MD = -0.539; 95% CI (-1.239, -0.161), I² = 0 %], and significantly improved cognition on a combined measure (ADAS-Cog with MMSE) [SMD = -0.289; 95 % CI (-0.551, -0.027), I² = 0 %].

CONCLUSIONS

In this meta-analysis, we demonstrated that MCTs can induce mild ketosis and may improve cognition in patients with mild cognitive impairment and Alzheimer's disease. However, risk of bias of existing studies necessitates future trials.

Effects of mycoprotein on glycaemic control and energy intake in humans: a systematic review

Mycoprotein is a food high in both dietary fibre and non-animal-derived protein. Global mycoprotein consumption is increasing, although its effect on human health has not yet been systematically reviewed. This study aims to systematically review the effects of mycoprotein on glycaemic control and energy intake in humans. A literature search of randomised controlled trials was performed in PubMed, Embase, Web of Science, Google Scholar and hand search. A total of twenty-one studies were identified of which only five studies, totalling 122 participants, met the inclusion criteria. All five studies were acute studies of which one reported outcomes on glycaemia and insulinaemia, two reported on energy intake and two reported on all of these outcomes. Data were extracted, and risk-of-bias assessment was then conducted. The results did not show a clear effect of acute mycoprotein on blood glucose levels, but it showed a decrease in insulin levels. Acute mycoprotein intake also showed to decrease energy intake at an ad libitum meal and post-24 h in healthy lean, overweight and obese humans. In conclusion, the acute ingestion of mycoprotein reduces energy intake and insulinaemia, whereas its impact on glycaemia is currently unclear. However, evidence comes from a very limited number of heterogeneous studies. Further well-controlled studies are needed to elucidate the short- and long-term effects of mycoprotein intake on glycaemic control and energy intake, as well as the mechanisms underpinning these effects.

Impact of ketosis on appetite regulation-a review

To reduce the health burden of obesity, it is important to identify safe and practical treatments that are effective for weight loss while concurrently preventing weight regain. Diet-induced weight loss is usually followed by a concomitant increase in ghrelin secretion and feelings of hunger, which may compromise weight loss goals and increase the risk of weight regain. The aim of this review is to describe the status of knowledge regarding the impact of ketosis, induced by diet or exogenous ketones (ketone esters), on appetite and the potential mechanisms involved. Ketogenic diets (KDs) have been shown to prevent an increase in ghrelin secretion, otherwise seen with weight loss, as well as to reduce hunger and/or prevent hunger. However, the exact threshold of ketosis needed to induce appetite suppression, as well as the exact mechanisms that mediate such an effect, has yet to be elucidated. Use of exogenous ketones may provide an alternative to KDs, which have poor long-term adherence due to their restrictive nature. Ketone esters have been shown to have concentration-dependent effects on food intake and body weight in rodent models, with effects becoming apparent when 30% of total dietary energy comes from ketone esters (threshold effect). In humans, acute consumption of a ketone ester drink reduced feelings of hunger and increased satiety compared to a dextrose drink. With the emerging widespread acceptance of KDs and exogenous ketones in mainstream media and the diet culture, it is important to fully understand their role on appetite control and weight management and the potential mechanisms mediating this role.

β-hydroxybutyrate Impedes the Progression of Alzheimer's Disease and Atherosclerosis in ApoE-Deficient Mice

β-hydroxybutyrate (β-OHB) has been shown to exert an anti-inflammatory activity. Apolipoprotein-E (ApoE) is strongly associated with atherosclerosis and Alzheimer's disease (AD). This study aimed to explore the therapeutic effect of β-OHB in the brain and the aorta of high-fat diet (HFD)-fed ApoE-deficient mice. We found in Apo-E deficient mice that β-OHB attenuated lipid deposition in the choroid plexus (ChP) and decreased amyloid plaque in the substantia nigra pars compacta. We also found decreased CD68-positive macroglia infiltration of the ChP in β-OHB-treated ApoE-deficient mice. β-OHB treatment ameliorated IgG extravasation into the hippocampal region of the brain. In vitro study using ChP mice cell line revealed that β-OHB attenuated oxidized low-density lipoprotein-induced ApoE-specific differentially expressed inflammatory ChP genes. Treatment with β-OHB reduced aortic plaque formation without affecting blood lipid profiles and decreased serum production of resistin, a well-established risk factor for both AD and atherosclerosis. Thus, the current study suggests and describes the therapeutic potential of β-OHB for the treatment of AD and atherosclerosis.