β-Hydroxy β-methylbutyrate free acid alters cortisol responses, but not myofibrillar proteolysis, during a 24-h fast

The Influence of Energy Balance and Availability on Resting Metabolic Rate: Implications for Assessment and Future Research Directions

Resting metabolic rate (RMR) is a significant contributor to an individual's total energy expenditure. As such, RMR plays an important role in body weight regulation across populations ranging from inactive individuals to athletes. In addition, RMR may also be used to screen for low energy availability and energy deficiency in athletes, and thus may be useful in identifying individuals at risk for the deleterious consequences of chronic energy deficiency. Given its importance in both clinical and research settings within the fields of exercise physiology, dietetics, and sports medicine, the valid assessment of RMR is critical. However, factors including varying states of energy balance (both short- and long-term energy deficit or surplus), energy availability, and prior food intake or exercise may influence resulting RMR measures, potentially introducing error into observed values. The purpose of this review is to summarize the relationships between short- and long-term changes in energetic status and resulting RMR measures, consider these findings in the context of relevant recommendations for RMR assessment, and provide suggestions for future research.

EXERCISE-INDUCED HORMONAL RESPONSES TO HMB ADMINISTRATION: A SYSTEMATIC REVIEW AND META-ANALYSIS

ABSTRACT Introduction: The β-hydroxy β-methyl butyrate (HMB) is an amino acid leucine metabolite with several ergogenic benefits. It is known that it can benefit testosterone and cortisol concentration in athletes. However, no systematic review and meta-analysis has focused on the effects of HMB supplementation on testosterone and cortisol in trained athletes. Objectives: The meta-analysis evaluates the effect of HMB supplementation on testosterone and cortisol in trained athletes and verifies conflicting results between studies. Methods: A systemic review was performed in Scopus, Medline, and Google scholar databases of articles published until August 2021. The Cochrane Collaboration tool was used to assess the risk of bias and assess the quality of the studies. Random effects model, weighted mean difference (WMD), and 95% confidence interval (CI) were used to estimate the overall effect. Results: Although the meta-analysis showed that HMB consumption does not alter cortisol and testosterone concentration, subgroup analysis based on exercise type exhibited a significant decrease in cortisol concentration in resistance training exercises (P<0.05) and a significant increase in testosterone concentration in combined aerobic and anaerobic sports (P<0.05). Conclusion: The results indicate that HMB supplementation in athletes can reduce cortisol concentration in endurance exercise and increase testosterone concentration in combined aerobic and anaerobic exercise. Evidence Level II; Therapeutic Studies – Investigating the results.

Testosterone and cortisol responses to ß‐hydroxy ß‐methylbutryate consumption and exercise: A meta‐analysis

Background

β‐hydroxy β‐methylbutryate (HMB) is a metabolite of leucine amino acid and it has several ergogenic benefits. Previous studies also showed that it may affect beneficially the testosterone and cortisol concentration in athletes. Due to the contradiction results between studies, we aimed to conduct this meta‐analysis to assess the HMB supplementation effect on testosterone and cortisol in trained athletes.

Methods

Scopus, Medline, and Google scholar were systematically searched up to August 2021. The Cochrane Collaboration tool for evaluating the risk of bias was applied for assessing the studies' quality. Random‐effects model, weighted mean difference (WMD), and 95% confidence interval (CI) were used for estimating the overall effect. Between‐study heterogeneity was evaluated applying the chi‐squared and I² statistic.

Results

Seven articles were included in the meta‐analysis. Although the meta‐analysis generally showed that HMB consumption did not have any effect on the cortisol and testosterone concentration (p > .05), subgroup analysis based on the exercise type showed a significant decrease in the cortisol concentration in resistance training exercises (WMD = −3.30; 95% CI: −5.50, −1.10; p = .003) and a significant increase in the testosterone concentration in aerobic and anaerobic combined sports (WMD = 1.56; 95% CI: 0.07, 3.05; p = .040).

Conclusion

The results indicate that HMB supplementation in athletes can reduce the concentration of cortisol in resistance exercises and increase the concentration of testosterone in aerobic and anaerobic combined exercises. Nevertheless, more studies are required to confirm these results.

Physiological responses to acute fasting: implications for intermittent fasting programs

Intermittent fasting (IF) is a dietary strategy that involves alternating periods of abstention from calorie consumption with periods of ad libitum food intake. There is significant interest in the body of literature describing longitudinal adaptations to IF. Less attention has been given to the acute physiological responses that occur during the fasting durations that are commonly employed by IF practitioners. Thus, the purpose of this review was to examine the physiological responses - including alterations in substrate metabolism, systemic hormones, and autophagy - that occur throughout an acute fast. Literature searches were performed to locate relevant research describing physiological responses to acute fasting and short-term starvation. A single fast demonstrated the ability to alter glucose and lipid metabolism within the initial 24 hours, but variations in protein metabolism appeared to be minimal within this time frame. The ability of an acute fast to elicit significant increases in autophagy is still unknown. The information summarized in this review can be used to help contextualize existing research and better inform development of future IF interventions.

Long-Term Effect of Combination of Creatine Monohydrate Plus β-Hydroxy β-Methylbutyrate (HMB) on Exercise-Induced Muscle Damage and Anabolic/Catabolic Hormones in Elite Male Endurance Athletes

Creatine monohydrate (CrM) and β-hydroxy β-methylbutyrate (HMB) are widely studied ergogenic aids. However, both supplements are usually studied in an isolated manner. The few studies that have investigated the effect of combining both supplements on exercise-induced muscle damage (EIMD) and hormone status have reported controversial results. Therefore, the main purpose of this study was to determine the effect and degree of potentiation of 10 weeks of CrM plus HMB supplementation on EIMD and anabolic/catabolic hormones. This study was a double-blind, placebo-controlled trial where participants (n = 28) were randomized into four different groups: placebo group (PLG; n = 7), CrM group (CrMG; 0.04 g/kg/day of CrM; n = 7), HMB group (HMBG; 3 g/day of HMB; n = 7), and CrM-HMB group (CrM-HMBG; 0.04 g/kg/day of CrM plus 3 g/day of HMB; n = 7). Before (baseline, T1) and after 10 weeks of supplementation (T2), blood samples were collected from all rowers. There were no significant differences in the EIMD markers (aspartate aminotransferase, lactate dehydrogenase, and creatine kinase) among groups. However, we observed significant differences in CrM-HMBG with respect to PLG, CrMG, and HMBG on testosterone (p = 0.006; η2p = 0.454) and the testosterone/cortisol ratio (T/C; p = 0.032; η2p = 0.349). Moreover, we found a synergistic effect of combined supplementation on testosterone (CrM-HMBG = -63.85% vs. CrMG + HMBG = -37.89%) and T/C (CrM-HMBG = 680% vs. CrMG + HMBG = 57.68%) and an antagonistic effect on cortisol (CrM-HMBG = 131.55% vs. CrMG + HMBG = 389.99%). In summary, the combination of CrM plus HMB showed an increase in testosterone and T/C compared with the other groups after 10 weeks of supplementation. Moreover, this combination presented a synergistic effect on testosterone and T/C and an antagonistic effect on cortisol compared with the sum of individual or isolated supplementation.

Effect of Ten Weeks of Creatine Monohydrate Plus HMB Supplementation on Athletic Performance Tests in Elite Male Endurance Athletes

Creatine monohydrate (CrM) and β-hydroxy β-methylbutyrate (HMB) are common ergogenic aids in the field of sports and are frequently used in an isolated way. However, there are a few studies that have investigated the effect of combining both supplements on different variables related to performance, with controversial results. Therefore, the main purpose of this study was to determine the efficacy and the degree of potentiation of 10 weeks of CrM plus HMB supplementation on sports performance, which was measured by an incremental test to exhaustion in elite male traditional rowers. In this placebo-controlled, double-blind trial, 10-week study, participants (n = 28) were randomized to a placebo group (PLG; n = 7), CrM group (0.04 g/kg/day of CrM; n = 7), HMB group (3 g/day of HMB; n = 7) and CrM-HMB group (0.04 g/kg/day of CrM plus 3 g/day of HMB; n = 7). Before and after 10 weeks of different treatments, an incremental test was performed on a rowing ergometer to calculate the power that each rower obtained at the anaerobic threshold (WAT), and at 4 mmol (W4) and 8 mmol (W8) of blood lactate concentration. There were no significant differences in WAT and W4 among groups or in body composition. However, it was observed that the aerobic power achieved at W8 was significantly higher in the CrM-HMB group than in the PLG, CrM and HMB groups (p < 0.001; η2p = 0.766). Likewise, a synergistic effect of combined supplementation was found for the sum of the two supplements separately at WAT (CrM-HMBG = 403.19% vs. CrMG+HMBG = 337.52%), W4 (CrM-HMBG = 2736.17% vs. CrMG+HMBG = 1705.32%) and W8 (CrM-HMBG = 1293.4% vs. CrMG+HMBG = 877.56%). In summary, CrM plus HMB supplementation over 10 weeks showed a synergistic effect on aerobic power (measured as WAT, W4, and W8) during an incremental test but had no influence muscle mass.

Effect of the Combination of Creatine Monohydrate Plus HMB Supplementation on Sports Performance, Body Composition, Markers of Muscle Damage and Hormone Status: A Systematic Review

Although there are many studies showing the isolated effect of creatine monohydrate (CrM) and β-hydroxy β-methylbutyrate (HMB), it is not clear what effect they have when they are combined. The main purpose of this systematic review was to determine the efficacy of mixing CrM plus HMB in comparison with their isolated effects on sports performance, body composition, exercise induced markers of muscle damage, and anabolic-catabolic hormones. This systematic review was carried out in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement guidelines and the PICOS model, for the definition of the inclusion criteria. Studies were found by searching PubMed/MEDLINE, Web of Science (WOS), and Scopus electronic databases from inception to July 3rd 2019. Methodological quality and risk of bias were assessed by two authors independently, and disagreements were resolved by third-party evaluation, in accordance with the Cochrane Collaboration Guidelines samples. The literature was examined regarding the effects of the combination of CrM plus HMB on sport performance using several outcome variables (athletic performance, body composition, markers of muscle damage, and hormone status). This systematic review included six articles that investigated the effects of CrM plus HMB on sport performance (two on strength performance, showing improvements in one of them; three on anaerobic performance, presenting enhancements in two of them; and one on aerobic performance, not presenting improvements), body composition (three on body mass, showing improvements in one of them; two on fat free mass, presenting increases in one of them; and two on fat mass, showing decreases in one of them) and markers of muscle damage and hormone status (four on markers of muscle damage and one on anabolic-catabolic hormones, not showing benefits in any of them). In summary, the combination of 3–10 g/day of CrM plus 3 g/day of HMB for 1–6 weeks could produce potential positive effects on sport performance (strength and anaerobic performance) and for 4 weeks on body composition (increasing fat free mass and decreasing fat mass). However, this combination seems to not show positive effects relating to markers of exercise-induced muscle damage and anabolic-catabolic hormones.

Time-restricted feeding plus resistance training in active females: a randomized trial

BACKGROUND

A very limited amount of research has examined intermittent fasting (IF) programs, such as time-restricted feeding (TRF), in active populations.

OBJECTIVE

Our objective was to examine the effects of TRF, with or without β-hydroxy β-methylbutyrate (HMB) supplementation, during resistance training (RT).

METHODS

This study employed a randomized, placebo-controlled, reduced factorial design and was double-blind with respect to supplementation in TRF groups. Resistance-trained females were randomly assigned to a control diet (CD), TRF, or TRF plus 3 g/d HMB (TRFHMB). TRF groups consumed all calories between 1200 h and 2000 h, whereas the CD group ate regularly from breakfast until the end of the day. All groups completed 8 wk of supervised RT and consumed supplemental whey protein. Body composition, muscular performance, dietary intake, physical activity, and physiological variables were assessed. Data were analyzed prior to unblinding using mixed models and both intention-to-treat (ITT) and per protocol (PP) frameworks.

RESULTS

Forty participants were included in ITT, and 24 were included in PP. Energy and protein intake (1.6 g/kg/d) did not differ between groups despite different feeding durations (TRF and TRFHMB: ∼7.5 h/d; CD: ∼13 h/d). Comparable fat-free mass (FFM) accretion (+2% to 3% relative to baseline) and skeletal muscle hypertrophy occurred in all groups. Differential effects on fat mass (CD: +2%; TRF: -2% to -4%; TRFHMB: -4% to -7%) were statistically significant in the PP analysis, but not ITT. Muscular performance improved without differences between groups. No changes in physiological variables occurred in any group, and minimal side effects were reported.

CONCLUSIONS

IF, in the form of TRF, did not attenuate RT adaptations in resistance-trained females. Similar FFM accretion, skeletal muscle hypertrophy, and muscular performance improvements can be achieved with dramatically different feeding programs that contain similar energy and protein content during RT. Supplemental HMB during fasting periods of TRF did not definitively improve outcomes. This study was prospectively registered at clinicaltrials.gov as NCT03404271.