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HMB: An Old Dog with New Tricks!


Dwayne N. Jackson, PhD


Intermittent fasting (IF) is one of the fastest-growing diet trends for fat loss. However, it generally means going for 12 to 24 hours without ingesting calories of any kind. Millions of people have benefitted from the rapid weight loss associated with IF, but restricting nourishment, especially without protein or amino acids for hours runs the risk of elevating cortisol (a catabolic hormone) and putting the body in a state of catabolism—potentially sacrificing your hard-earned gains. A recent study published in The British Journal of Nutrition suggests that β-Hydroxy β-methyl butyrate, commonly known as HMB- Free Acid (HMB-FA), may be an ideal supplement for those who partake in the practice of IF.



For those of you who don’t know, HMB is an active anabolic metabolite of the essential branched-chain amino acid leucine, which resides in all human muscle cells. HMB is found in foods like avocado, alfalfa, catfish, and citrus fruits. In a recent study, researchers from Texas Tech University assessed the effects of HMB-FA supplementation on catabolism (muscle breakdown), cortisol release, testosterone (an anabolic hormone), and resting energy expenditure (REE), during a period of acute fasting.  Eleven healthy males and females participated in this randomized, double-blind, and placebo-controlled cross-over trial, where they received an HMB-FA supplement or a placebo (1g, 3x/day) during a 3-day meat-free diet, followed by a 24-hour fast.


Urinary HMB concentrations confirmed compliance with supplementation. Interestingly, markers of catabolism were unaffected by acute fasting, so there was no observed impact of HMB on muscle breakdown. However, with HMB supplementation, the fasting cortisol response was blunted by 32%, with no effect in the placebo group! In males, the testosterone to cortisol ratio (T: C) increased 162% from 0 to 24 h of fasting with HMB-FA, but not placebo, this was mainly due to reductions in cortisol.


ACTION POINT: So, if you are using IF as a dieting strategy or if you just want to keep cortisol managed, it seems that HMB-FA might provide some supplemental support. According to HMB research, the best to dose HMB is at 38 mg/kg body mass (approximately 17 mg/lb) of body weight daily, split into 3 equal doses. Take 1 dose 30-60 before training, another immediately after training, and another with a meal. On rest days, take your 3 doses with breakfast, lunch, and dinner. You will notice the greatest effects of HMB after 2 weeks of supplementation and chronic consumption is deemed safe.



Tinsley G, Givan AH, Graybeal AJ, Villarreal MI, Cross AG. β-Hydroxy β-methyl butyrate free acid alters cortisol responses, but not myofibrillar proteolysis, during a 24-h fast. Br J Nutr. 2018 Mar;119(5):517-526.




BCAAs: Friends with benefits!


Of the 9 essential amino acids, the three BCAAs: leucine, isoleucine, and valine, play a key role in protein synthesis and energy metabolism— accounting for approximately 20% of your total protein intake (dairy has an abundance of BCAAs). BCAAs also make up about 35% of the essential amino acids in muscle proteins and 40% of the human requirement for preformed amino acids, which is why they’re so critical for athletes.


BUT…..BCAAs are much more than components of proteins, in fact, most of the benefits for athletes come from their direct impact on energy production and fatigue resistance, noted when taken pre-workout.  BCAAs are readily broken down (catabolized) during exercise. The status of BCAA breakdown is dependent on the branched-chain alpha-keto acid dehydrogenase complex (BCKDH) activity, which is relatively dormant under resting conditions and becomes activated with exercise. When we train hard, BCAAs are reduced to their basic components and are used as fuel. Based on this fact alone, it’s obvious why BCAA supplementation may benefit those undergoing a heavy exercise regimen: They’re being used for energy purposes, so you better have enough of them hanging around. Either you supply them by taking BCAAs as supplements or your body will find them on its own – and by that route, it will strip them off protein chains that could have instead been used for building muscle.


Over the past decade, BCAA supplements have been shown to help with fat burning, energy production, fatigue, glucose regulation, glucose transportation, gut health, embryo development, and immunity!


ACTION POINT: As always we recommend taking 5-10 g of BCAAs, 3 times per day, in the form of 2:1:1 Leucine:Isoleucine: Valine. On rest days, take BCAAs once in the morning and 2 other times throughout the day between meals (for a shot of energy). On training days, take 5-10g pre-workout and another 5-10g Intra workout. For an added Intra workout anabolic spike, take 5g of BCAAs with 5 grams of essential amino acids during your training session. Post-workout, take 20-30 g of Whey Protein Isolate, which naturally contains high levels of BCAAs.



Zhang S, Zeng X, Ren M, Mao X, Qiao S. Novel metabolic and physiological functions of branched-chain amino acids: a review. J Anim Sci Biotechnol. 2017 Jan 23;8:10. doi: 10.1186/s40104-016-0139-z. eCollection 2017.




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